My first self made EVAP

[MikeHolm]

It's my first EVAP, just a fan, TXV, sensors and coil. Everything else is indoors but i won't show that to you yet as the wiring sucks and I have to clean it up:D Take note BF.

[chillerman2006]

Hi Mike

nice shiny black mate looks pretty and neat job

picture is decieving - is there an opening at the bottom for air intake

at first glanc it looked like it was sitting on the ground and balancing

on 6 inches of earth. haha my eyes, must be age catching me up

R's Chillerman

[MikeHolm]

It is off the ground by about 24" for drainage and it's British racing green, being a 60's BRM and Lotus fan, I thought that appropriate. Quiet as a church mouse. I was wondering if anyone would say anything....except for mumbling "what a pile of shyte":D

[chillerman2006]

now you say it, my eyes can see its brg

whats 'brm' ?

and now my turn for the questions, with a cooling system you select the evap for required work

then add compressor/condensor/txv to match

How do you design a heat pump ?

Do you start with the condensor and then match components ?

R's chillerman

[chilliwilly]

Did you make the coil yourself or did you buy it?

[MikeHolm]

now you say it, my eyes can see its brg

whats 'brm' ?

and now my turn for the questions, with a cooling system you select the evap for required work

then add compressor/condensor/txv to match

How do you design a heat pump ?

Do you start with the condensor and then match components ?

R's chillerman


BRM was British Racing Motors who made some great racers in the 50s and 60s and Lotus is....well....Lotus.

I had a comp from a 12kw (give or take) heat pump that someone smashed up badly. it is a ZP40 and the only other good thing in it was the TXV and a couple of pressure switches. That was my starting point and the house is not too large so it may be a reasonable fit.

I used the least scientific method available to determine the coil, I added up the tubing surface area of the busted up wrap around (standard north american type) and the aluminum fin surface area and the volume of the tubing and using all the discussions with all you guys and a s**tload of research, I drew up the coil and had it made by a local establishment. I'll look for a coil end photo to post but I basically wanted a horizontal coil which appears to be the best for defrosting. The coil is 30" by 60", 4 row, 2 evenly split runs.

It will still take me a long time to get used to things like coolpacks so I didn't rely on it for anything although I tried. I don't know enough yet to use it with any certainty.

I picked 40C as my target temp for the buffer (450L, UFH and no dhw). I used the SWEP design software for the condenser (which I think may be a little bit small, but we will see as the year goes on) and I have bought lots of Hx from them before so I like the product. I cheated in that I didn't have to size a TXV (assuming my evap is sized right) so we will have to see how it runs, so far so good.

Real seat of the pants flying.

[chillerman2006]

Hi Mike

your method appears logical mate

you have evap/comp/txv already matched, replaced evap with equal volume evap

then matched condensor to system, an half educated thought would be on setup

you will need to balance the system by air flow across evap and suction superheat/mass flow

to get your desired condensor temp but taking into account compressor protection

nice one mate, design is way beyond me now but maybe one day :)


R's chillerman

[MikeHolm]

Thanks CM, I know my liquid fluid flow quite well but I'm still a novice in the "art" of refrigeration so it is actually a big step for me (old hat for many here I suspect)

[Bigfreeze]

It's my first EVAP, just a fan, TXV, sensors and coil. Everything else is indoors but i won't show that to you yet as the wiring sucks and I have to clean it up:D Take note BF.

Nicely done Mike. You'll have good defrost draining from that design and protection from snow. Also the height of the ground and lack of legs makes a back build of ice also impossible. Good work mate.

If only I could progress my own projects as quickly:o

[Goober]

What a pile of shyte!

Sorry...couldn't resist. It is very nice looking though.

[mad fridgie]

Where is the fan, is this induced draft or forced draft.?
The does the air blow up out of the evap or down out of the evap?

[mikeref]

Mike, this now explains why you are difficult to find. Goober, just keep that office chair polished ;) and think about the fun you are missing out on by not being on the tools :p..Mike.

[MikeHolm]

7900
It had just finished raining so it looks wet. it is an updraft VSD unit. I haven't gotten to insulating the piping when i took the pic but it's done now.

[MikeHolm]

All this will put me in the poor house for sure but it is great fun. I love the challenge.

[mad fridgie]

Lets look at this as a purist
We do we want for efficiency, the highest possible air entering temperature, and air that is easiest to move.
So ,looking at the picture we can see that we are in fact pulling the coldest possible air (from the ground and recirculated air) into the evap coil, and driving air against its natural tendency to fall. air will fall naturally out of the evap coil.

[chillerman2006]

Hi Mike

did not want to load up your thread with info you already have

so have started a new one, some maybe of assistance

http://www.refrigeration-engineer.com/forums/showthread.php?33278-Heat-Pump-Theory

Also the attached doc is referring to uk temps that rarely hit minus 15*c (norm -5*c where I am)

& lists ashp's as not economical with low ambients !

R's chillerman

[MikeHolm]

Lets look at this as a purist
We do we want for efficiency, the highest possible air entering temperature, and air that is easiest to move.
So ,looking at the picture we can see that we are in fact pulling the coldest possible air (from the ground and recirculated air) into the evap coil, and driving air against its natural tendency to fall. air will fall naturally out of the evap coil.

The air movement as you state will be working against nature so I suspect the electrical draw might be a little bit higher but given the current draw I doubt it will be much. I haven't seen any heat pumps here that would be a downdraft because they are almost the units are offshoots of AC units.

The ground temp at the house will be a few deg warmer than the ground 1m away from the house because it is not that well insulated. I had contemplated having the heat recovery exhaust exit the house under the unit or even within the box but it was technically difficult to do.

If your air on and air off temps are only a few deg different and given the heat loss of the building at ground level (there is a full basement), I'm not sure that it will be an issue. 25 years ago we regularly had temps of -25 in the depths of the winter but the last few winters I can count very nights below -15C with most at -5 to -10. I use -15 as a goal which is why I was interested in the digital scrolls performance.

[MikeHolm]

Hi Mike

did not want to load up your thread with info you already have

so have started a new one, some maybe of assistance

http://www.refrigeration-engineer.com/forums/showthread.php?33278-Heat-Pump-Theory

Also the attached doc is referring to uk temps that rarely hit minus 15*c (norm -5*c where I am)

& lists ashp's as not economical with low ambients !

R's chillerman


CM, the description as written probably needs some editing as it may be more true in the American context but from what I have seen, European heat pumps are designed quite differently. American units focus on air heating, starts with cooling (residential units) and heating usually an afterthought. I may be wrong but most of the resi HPs in Europe use a slab coil for the evap (comp indoors and designed for heating load) and most US ones use a wrap around coil with the comp in the middle.

[MikeHolm]

Lets look at this as a purist
We do we want for efficiency, the highest possible air entering temperature, and air that is easiest to move.
So ,looking at the picture we can see that we are in fact pulling the coldest possible air (from the ground and recirculated air) into the evap coil, and driving air against its natural tendency to fall. air will fall naturally out of the evap coil.

Mad, what do you think the performance change would be if the the fan was removed from the picture?

[mad fridgie]

What yo have built is an excellent cond, (and this is what everybody does, even in this application)
Here NZ the ground temp in the morning can be a good 6C below air temp,
So for example if the fan where underneath, drawing air downwards and discharging along the ground, it is possible that the SST could be 6C higher (in the above case), that could increase duty by close to 15%.
(off the top of my head)

[MikeHolm]

What yo have built is an excellent cond, (and this is what everybody does, even in this application)
Here NZ the ground temp in the morning can be a good 6C below air temp,
So for example if the fan where underneath, drawing air downwards and discharging along the ground, it is possible that the SST could be 6C higher (in the above case), that could increase duty by close to 15%.
(off the top of my head)


Food for thought, as they say, I will have to look up norms but local temps (local meaning within a 1m or so) are very influenced by what is around them. Is the wasted heat through the wall of the house going to influence the air on temp when the coil is 600mm above the ground. I have never seen a study on this but I am sure it exists....somewhere

[Bigfreeze]

I'd have to disagree with you there Mad. There would be almost no difference in the air temp a 300mm off the ground and that off air 1.3m off the ground. I would say almost none tbh. The disadvantage of downdraft in Mikes design is that it could encourage short cycling of air, which would be much worse than any potential gain.

[MikeHolm]

I'd have to disagree with you there Mad. There would be almost no difference in the air temp a 300mm off the ground and that off air 1.3m off the ground. I would say almost none tbh. The disadvantage of downdraft in Mikes design is that it could encourage short cycling of air, which would be much worse than any potential gain.

Even tho it is 600mm off the ground and has free air on 3 sides? Maybe i am not getting the meaning of short cycling correct...

[chillerman2006]

Hi Mike

obviously these Gents understand these systems well

what I can see from their comments are

updraught could short cycle if air off is not ejected far enough away from the unit, as air off being cooler than ambient will natuarally fall once out of air flow - induced draught in this case would through the air further (I think)

downdraft could short cycle if unit is too close to the ground and in the morning when the ground is cooler than ambient and air off

but once the ground is at or above ambient then the air should naturally disperse along the ground

stuck in between two possiblities here, I would be inclined to go for down draft

I would then use a smoke stick, to be sure of air flow and if short cycling still then add a chimney to the air on

Once all finalised the unit and chimney if required can be covered and made to fit in with the surroundings

your other point mentioned of wrap around coil seems to also have advantage, as wasted heat from the compressor can be transfered to the evap, but not something you considered ?

R's chillerman

[MikeHolm]

CM, the wrap around coil is a space saver but does nothing for ability to defrost properly which, going through most of the problem posts here, is the root of the issue. Short and effective defrost is one key to a trouble free cost efficient system. There are benefits to a downdraft in terms of fan electrical cost but it think it is slim at this point.

[mad fridgie]

I'd have to disagree with you there Mad. There would be almost no difference in the air temp a 300mm off the ground and that off air 1.3m off the ground. I would say almost none tbh. The disadvantage of downdraft in Mikes design is that it could encourage short cycling of air, which would be much worse than any potential gain.
The comment is not particular to this evap, The air is drawn past the ground to enter the evap, hence must be colder, the air exiting is colder and more dense than the ambient so will fall to low level, encouraging short cycling.
Many other factors do need to be considered exiting air velocity, free area in which it is to be mounted.
Not to say that you would just mount the fan underneath.

[MikeHolm]

Here is the next Evap I had in mind,
7921

In the winter The solar panels are often unable to reach the temp needed to help the DHW tank but does contain enough heat to add to the evap. The question is, at what sustained temp would the coil be considered to be overheated? 40C? Assume 410A. Probably not enough info;) typical eh...

[chillerman2006]

CM, the wrap around coil is a space saver but does nothing for ability to defrost properly which, going through most of the problem posts here, is the root of the issue. Short and effective defrost is one key to a trouble free cost efficient system. There are benefits to a downdraft in terms of fan electrical cost but it think it is slim at this point.
Hi Mike

I was not thinking of defrost issues when commenting on wrap arounds, as I am still playing catch up with you's on HP's

not knowing/seeing how wrap arounds are configured, I was thinking of compressor heat, how ever minimal transfered to the cooling coil, would be a welcome increase at low ambients

I know I am missing a big part here (again) with defrost issues (still to learn) but I would have thought mounting in the traditional upright way on the houses wall, would be beneficial, as you would then have the warmest air possible as air on, that being warmer than ambient due to heat loss of the property... My reasoning here is if I park my vehicle facing the house my windscreen rarely freezes with minus ambients but if facing away it always freezes

R's chillerman

[MikeHolm]

Hi Mike

I was not thinking of defrost issues when commenting on wrap arounds, as I am still playing catch up with you's on HP's

not knowing/seeing how wrap arounds are configured, I was thinking of compressor heat, how ever minimal transfered to the cooling coil, would be a welcome increase at low ambients

I know I am missing a big part here (again) with defrost issues (still to learn) but I would have thought mounting in the traditional upright way on the houses wall, would be beneficial, as you would then have the warmest air possible as air on, that being warmer than ambient due to heat loss of the property... My reasoning here is if I park my vehicle facing the house my windscreen rarely freezes with minus ambients but if facing away it always freezes

R's chillerman

Take a look at most of the people coming on with a poorly preforming HP. A big majority use Japanese (or their Chinese knock offs) HPs with placement or airflow issues due to defrost.

Google any york or lennox AC unit and you will see a picture. I would say they make up 95% of North American HPs.

[al]

mike

i love the build, you're going to find out so much from this!!

This is something i saw last year:

http://www.irishecoplumbing.com/thermodynamic-solar-panels

Have you seen these BigFreeze?

as i said before, best air source i've seen, standard cold room evaporator outside with a condensing unit made from off the shelf parts.

al

[chillerman2006]

This is something i saw last year:

http://www.irishecoplumbing.com/thermodynamic-solar-panels

Have you seen these BigFreeze?

as i said before, best air source i've seen, standard cold room evaporator outside with a condensing unit made from off the shelf parts.

al

Hi Al

it all looks very neat......but So Much of it ! (massive)

I am at early stages of deciding what to fit to my house

and this lot would turn a large double room into a single or loose half my garage !

Would I need all this for a 3 x double bed house ???

R's chillerman

[MikeHolm]

Al, do you know this guy? Irish EcoPlumbing? It looks like a neat enough job but the there is no way that the panel does much for the system.

It is basically the same performance as a plastic swimming pool panel, and you need 20m2 to get any heat from them. Also, because they are not enclosed in a greenhouse (glass, insulation, aluminum frame etc) like water heating panels are supposed to be (or vacuum tubes), they will only work during sunny periods when the ambient is above 15C. Otherwise they will re-emit as much energy to the environment as they absorb. I really hope no one buys it. It can be improved but it is an iffy technology as is.

I spoke a bit too soon....

Just had a look at the system and it is a 134A based panel that looks like it is about 1m2 or so. I suspect that while it would get more heat output than a regular system of the same size, would it be 8 times? doubtful. also, how would they deal with fridge lines that go up 3 storeys, for example). Knowing how many issues we have with regular solar systems, this one must have been fun to perfect.

[MikeHolm]

CM, you have seen my website. There are lots of pics of 2 panel systems that would provide 50-70% of the DHW for your house. If you want to tie it in with a heat pump, it will be more involved but whatever you do, if you want to use solar for space heating you should have a lot more panel area and 75-100L of storage for every m2 of panel area. There are some exceptions to this rule but it would involve a trip to the UK, and lots of beer.:D

[al]

MikeH

There's a guy by the name of quentin gargin (fairly unique name!), he's based in west cork and knows lots about renewables, i've spoken briefly with him and come to the conclusion that solar isn't economical at the minute.

i don't know who is behind the product i mentioned, just purely as a different way of looking at it, i have the same questions about ice buildup etc.

CM, if you can get all that gear at cost price then go for it but it wouldn't be for me! Reinsulate the house first, then worry about heating.

al

[al]

Some interesting debate here and some good info too:

http://www.boards.ie/vbulletin/forumdisplay.php?f=1041

not sure if you have to register to view or not.

al

[chillerman2006]

Hi Mike

argh, am with it now thanx

was looking at that lot for just an ashp set up and was shocked

now I see its solar heating too, will have a closer look through your site tomorrow, cheers

bed for me now and will speak with the brewery here asap

R's chillerman

[chillerman2006]

CM, if you can get all that gear at cost price then go for it but it wouldn't be for me! Reinsulate the house first, then worry about heating.

al

Hi Al

very good point mate, not long fitted (2year ago) new hot water/heating system

and loft and walls need insulating for sure, cheers

R's chillerman

[Bigfreeze]

mike

i love the build, you're going to find out so much from this!!

This is something i saw last year:

http://www.irishecoplumbing.com/thermodynamic-solar-panels

Have you seen these BigFreeze?

as i said before, best air source i've seen, standard cold room evaporator outside with a condensing unit made from off the shelf parts.

al

Have seen them alright Al. Same principle as the ice stick and same fundamental problem, once the outside temp goes to 7C or under you get ice formation on the panel which causes evap temp to drop, which creates more ice and so on so forth. I looked at something similar myself years ago but passed on them as they are only good for producing hot water in mild weather.

The reason a cold room evap works well is that its designed to work with moisture. Most AC type units aren't.

[Bigfreeze]

Hi Al

very good point mate, not long fitted (2year ago) new hot water/heating system

and loft and walls need insulating for sure, cheers

R's chillerman

Have you rads or ufh CM?

[al]

That was what i thought BF, i wonder could you harness solar to defrost the unit, but on overcast days you're still left with an iced evaporator and bugger all heat.

al

[Bigfreeze]

The investment isn't worth it and on warmish days they'll pretty much defrost themselves. Best bet is to avoid air to waters as much as possible in the first place and fit ground loops where possible. Simplifies everything and better returns.

[chillerman2006]

Hi BF

I have all new rads with individual stats

R's chillerman

[chillerman2006]

That was what i thought BF, i wonder could you harness solar to defrost the unit, but on overcast days you're still left with an iced evaporator and bugger all heat.

al


The investment isn't worth it and on warmish days they'll pretty much defrost themselves. Best bet is to avoid air to waters as much as possible in the first place and fit ground loops where possible. Simplifies everything and better returns.

Gents

I have no water meter and was wondering my mains supply stays between 10*c & 16*c all year round

would this suit a wshp, although I presume the water board would not appreciate my usage (if they knew)

R's chillerman

[Bigfreeze]

You'd probably need about 2000L per hr for a water source unit CM, so you'll never run it from the mains.

I'd also second Al's advice and say put your money into insulation first. A poorly insulated house with rads is a no no for a heat pump no matter what some manufacturers and salesmen will tell you. You can look at a HP down the line, but bring your insulation level as high as possible first.

[chillerman2006]

Hi BF

thanx mate, I will get the insulation sorted, loft first, probably this/next weekend and look into getting the walls done asap, not happy with this gas system though as a couple of years back, gas was about £80 a month in winter, this summer its been £40 a month for hot water (3 x baths a day)....Got the boiler serviced and it shot up £80 a month......twat that serviced it, upped the system pressure and when heating, it lifted the prv and never closed as the filler loop was not capped off and was letting by, first I new about it was when I found green algae on back of house on day off....she said ''thats been like that for months, I wondered what the water was'' :(

Have it all sorted now but still £40 a month without heating, Gas is just toooo expensive

R's chillerman

[Bigfreeze]

Hi BF

thanx mate, I will get the insulation sorted, loft first, probably this/next weekend and look into getting the walls done asap, not happy with this gas system though as a couple of years back, gas was about £80 a month in winter, this summer its been £40 a month for hot water (3 x baths a day)....Got the boiler serviced and it shot up £80 a month......twat that serviced it, upped the system pressure and when heating, it lifted the prv and never closed as the filler loop was not capped off and was letting by, first I new about it was when I found green algae on back of house on day off....she said ''thats been like that for months, I wondered what the water was'' :(

Have it all sorted now but still £40 a month without heating, Gas is just toooo expensive

R's chillerman

Not sure of gas or oil prices in the UK but here in Ireland you need a COP of 2.2 to match oil and with the upcoming increases in electricity you'll need a COP of 2.5-2.6. You won't match that in cold weather with an air source heat pump and rads, so investing in one is wasted money, especially where insulation is poor.

Insulate the nuts out of it, see whats the lowest temp you can manage to keep the rads at and keep the house warm and then you can decide whether a HP is suited. Any possibility of drilling a borehole?

[chillerman2006]

Not sure of gas or oil prices in the UK but here in Ireland you need a COP of 2.2 to match oil and with the upcoming increases in electricity you'll need a COP of 2.5-2.6. You won't match that in cold weather with an air source heat pump and rads, so investing in one is wasted money, especially where insulation is poor.

Insulate the nuts out of it, see whats the lowest temp you can manage to keep the rads at and keep the house warm and then you can decide whether a HP is suited. Any possibility of drilling a borehole?

Hi BF

I dont know pricing here or how it works out either, all I know is the system I got was supposed to be more efficient (condensing boiler) yet my bills have doubled in two years, with gas price increases, so am at a loss to know if and how much benefit I have out of this system, the new rads I presume were a good choice as others were at least 15 years old and rooms heat quicker now, although having three floors is a pain as each floor is hotter than one below

Should be able to drill a borehole here mate, as there is rear access and as far as aware no obstuctions, the sewage runs through each rear garden but only about 1.5 metres from house. A figure of 16*c comes to mind (cant recall why) with gshp. What sort of depth/temp would I need for gshp and am wondering now also, why Mike has not taken this route with such low ambients

Mike

was this not an option for yourself or was it you just wished to overcome the issues of ashp

R's chillerman

[Bigfreeze]

I think Mikes issues lied with the cost of drilling in Canada, local regulations and drillers just being difficult to work with in general.

If you give me the insulation spec and dimensions for the house I'll do a heat calc for you and work out a borehole depth and HP size

[MikeHolm]

Hi BF

thanx mate, I will get the insulation sorted, loft first, probably this/next weekend and look into getting the walls done asap, not happy with this gas system though as a couple of years back, gas was about £80 a month in winter, this summer its been £40 a month for hot water (3 x baths a day)....Got the boiler serviced and it shot up £80 a month......twat that serviced it, upped the system pressure and when heating, it lifted the prv and never closed as the filler loop was not capped off and was letting by, first I new about it was when I found green algae on back of house on day off....she said ''thats been like that for months, I wondered what the water was'' :(

Have it all sorted now but still £40 a month without heating, Gas is just toooo expensive

R's chillerman


CM, get rid of your vented system(it is really old school), just cap it then put in an expansion tank on the return side of the boiler and you will have a more stable system and no risk of corrosion in those steel rads of yours.

[chillerman2006]

I think Mikes issues lied with the cost of drilling in Canada, local regulations and drillers just being difficult to work with in general.

If you give me the insulation spec and dimensions for the house I'll do a heat calc for you and work out a borehole depth and HP size

Hi BF

that will be great thanx, will get the insulation all done first, mate

R's chillerman

[MikeHolm]

I think Mikes issues lied with the cost of drilling in Canada, local regulations and drillers just being difficult to work with in general.

If you give me the insulation spec and dimensions for the house I'll do a heat calc for you and work out a borehole depth and HP size

Yea, BF is right, all of the above but also, where I work the houses can have quite a small area for drilling and our code is that we must design for -20C even tho we rarely see it. The average house here would need 4-5 boreholes 200-250ft deep to meet the loads and the holes MUST be at least 10ft apart to keep from freezing the ground.

[chillerman2006]

Yea, BF is right, all of the above but also, where I work the houses can have quite a small area for drilling and our code is that we must design for -20C even tho we rarely see it. The average house here would need 4-5 boreholes 200-250ft deep to meet the loads and the holes MUST be at least 10ft apart to keep from freezing the ground.

Hi Mike

wow! when BF first mentioned borehole to me, my first thought was I wonder if I can dig that myself :confused: and save some money.... I would not have needed any heating for the house, I would have finished my days out digging my life away, haha:D

R's chillerman

[MikeHolm]

Much easier where the heat loads are lower, like most of the UK. Some areas here have design temps of -35 to -40 so it is a bit of a chore to design the system but that is not the norm.

Seriously, for your system, right now you can adjust things to lower the bill. How big is the house and what is the boiler input?

[chillerman2006]

CM, get rid of your vented system(it is really old school), just cap it then put in an expansion tank on the return side of the boiler and you will have a more stable system and no risk of corrosion in those steel rads of yours.

Hi Mike

missed this post earlier, mate

I have an expansion tank in the tank cupboard along with the pump

am presuming now its an expansion tank

if it is, can I just cap off the overflow/prv outlet ?

R's chillerman

[MikeHolm]

Now you have me a bit confused. I think that what I am looking at is a DHW cylinder, pump and an expansion tank. In some places there is a check valve (non return valve I think you call it) on the cold water coming in and to take up expansion when the tank heats up the exp tank must be there. But this may have nothing to do with space heating (not enough info).

Where is the boiler? Is there a heat exchanger in the tank?

[chillerman2006]

Hi Mike

house is three storeys, tank in picture above is on 1st floor, boiler is on ground floor, dimensions are 6x8 metres (per floor) could not find any info on bolier apart from model, as on attached pic...this was a right bogit & scarper install by one of her relatives, who dare not come round since and face me, wrecked the house, holes left in ceiling, ran skill saw along next to joists, then screwed 2x2 timber to joists and relayed floor, carpet deteriated along the gaps left behind, [deep breath] but still better than what was here which was gravity fed system with tank on first floor, very little flow to 2nd floor!

I think there is heat exchanger in tank, as bolier is not a combi boiler

R's chillerman

[MikeHolm]

OK, that boiler is a Baxi product with a max output of 15kw. IF your house is enclosed on two sides and the windows and air infiltration are reasonable, it should have no trouble keeping up with the demand. I see from the pic that there is a 3 way valve that divides between the heating the tank and the rads. I assume that the valve is normally set to heating.

Was the tank there before or or it new? Often tanks like that have a small HX and the boiler must stay on quite a while and at high temp to keep it heated. It is also possible that the setup syphons heat from the tank to the rads and the tank must call for heat more often. That part is just conjecture in regards to your system.

Why did the service guy turn up the gas pressure or was it just the water pressure?

[chillerman2006]

Hi Mike

the water tank was installed with boiler and yes it heats house no problem, in the winter I leave heating on 24/7 and just control temp via rad stats, one rad in hallway groundfloor has no rad stat, main wall stat normally set to, 21-25*c....yes inclosed 2 sides and new double glazing windows and doors, both heating and hot water work/heat up quickly

I called for service due to high gas bills this year and he adjusted the water pressure but left filler loop connected afterwards and this was now letting by, increasing system to mains water pressure, and when boiler came on, lifted prv and she just watched hot water come out of overflow for months, before I spotted algae on rear wall of house

Even though it works ok, I want to rip it out and start again at some point and I dont want any tube connections under the floor as want to lay new floor boards through out and dont want them lifted for anything once laid, I also have water tank in the loft/attic that I want shot of, which currently gravity feeds cold water to hot water tank/bathroom and toilets...the kitchen and boiler are all thats on mains water

need to work out what would be best to install here and get it all fitted next summer

R;s chillerman

[knighty]

what;s your boiler temperature set to ?

anything more than 55'C and the boiler stops being a condensing boiler and just acts as a normal boiler
(return water is too hot for the hot moisture to condense on) and efficiency plummets (lower than a normal boiler)

also, make sure that stat on your hot water tank is set lower than the boiler temperature !


when my parents had there new heating installed, the boiler was set to 60'c, but the hot water tank to 80'C... so the tank always called for more heat, but the boiler could never take it over 60'c....

the boiler ran 27/7 trying to heat the hot water tank up.... I knocked it down to 50'C and now the boiler hardly ever runs ! :-)


can you take some more photos of the tank and plumbing there ?


by the look of it (and some of it is guess work here because I can't see everything)

you have a system boiler - so it just heats the same water pumping it round and round...

the 3 way valve picks where the water coming out of the boiler goes... it'll either go through the hot water tank heat exchanger or through the radiators.... there'll normally be a pressure valve here too so if there's a flow restriction etc.. some of the water will bypass from just before the valve and back down the return to the boiler (some valves can even split the flow between the tank/radiators)

if you have mains pressure hot water (looks like you do) the cold water into the bottom of your tank will come straight from the water main, with a non return valve and your expansion tank connected just after it (to take the pressure as the water heats and expands)

but... it looks a bit like your expansion tank is fitted to the heating water... I've never seen a system like that before.... but I'm not a heating engineer so it could be normal... you only need a small expansion tank here... and most boilers have one internally...

[chillerman2006]

Hi Mike

what temp can I take tank down to ?

boiler is mains fed for (manual) top up only, tank is gravity fed from water tank in loft

could be half my problem is 3 storey town house,

when its comfortable on ground floor, 1st floor is hot and top floor baking!

thinking of ducting top floor to ground in attempt to balance it out

R's chillerman

[MikeHolm]

There is a lot here.
First,if the boiler is set to 50-52 and the tank is set to 50, it won't turn off. Either increase the boiler temp or decrease the tank temp at least 5 deg.

Second, what is the mains pressure? It needs to be 2.5- 3 bar for the DHW to work properly and the heating for a 3 story house needs to be minimum of 1.2bar. It is possible that the mains is low and the exp tank is there for that but i doubt it. One problem is that you appear to have both an bladder type exp tank (which is turned upside down and should not be) and a old style fill tank on the top floor.

As I said before, get rid of the top one and cap the line. How many rads do you have in the house? I suspect you need a bit bigger exp tank than the white one, probably 25L or so as there is none in the boiler. You will need a pressure reducing valve from the cold water to the heating loop (placed beside the exp tank and all this should be on the suction side of the pump).

Condensing boilers do need to run at lower temps then non condensing but unless your natural gas is different than ours (which I doubt), condensing will start at 60C return water temp and gets better as you go down in temp. Even if you run the boiler at 80C you still will not get worse than the non condensing boiler but you are wasting energy.

[MikeHolm]

EXP tank in pic is on the wrong side of the pump. Turn down the stats on the top floor (DUH, I'm sure you have done that already.) I assume the boiler is not weather compensated>

Off to work now so i will blab on more when i get home.

Cheers

[chillerman2006]

There is a lot here.
First,if the boiler is set to 50-52 and the tank is set to 50, it won't turn off. Either increase the boiler temp or decrease the tank temp at least 5 deg.

Second, what is the mains pressure? It needs to be 2.5- 3 bar for the DHW to work properly and the heating for a 3 story house needs to be minimum of 1.2bar. It is possible that the mains is low and the exp tank is there for that but i doubt it. One problem is that you appear to have both an bladder type exp tank (which is turned upside down and should not be) and a old style fill tank on the top floor.

As I said before, get rid of the top one and cap the line. How many rads do you have in the house? I suspect you need a bit bigger exp tank than the white one, probably 25L or so as there is none in the boiler. You will need a pressure reducing valve from the cold water to the heating loop (placed beside the exp tank and all this should be on the suction side of the pump).

Condensing boilers do need to run at lower temps then non condensing but unless your natural gas is different than ours (which I doubt), condensing will start at 60C return water temp and gets better as you go down in temp. Even if you run the boiler at 80C you still will not get worse than the non condensing boiler but you are wasting energy.

Hi Mike

turned boiler off and used some hot water, static pressure is 1.4bar

tank set to 50*c, turned on boiler

and cut out at flow 72*c and return 61*c with pressure @ 1.8bar

Temps taken with strap probes 10cm from boiler and pressure gauge is on return

mains water pressure here is over 5bar

am pretty sure tank fill comes from loft/attic cold water tank, which gravity feeds from roughly 6 metres above and feeds into rear/bottom of HW tank

there are 7 rads (6 x rad stats, hallway ground floor no rad stat, runs off wall stat on first floor)

top floor rad stats now set to 3 of 5 and blob silicone so can check they not been fiddling with them

and will get the DHW set up on mains with pressure reducing valve and do away with loft tank and move expansion tank to other side of pump, this summer as I can send them on holiday then whilst I get it all sorted

for now turning boiler down to 55*c and tank to 45*c, should see some improvement ?

you say exp tank is upside down, is this an issue ?
thanx mate :)

R's chillerman



EXP tank in pic is on the wrong side of the pump. Turn down the stats on the top floor (DUH, I'm sure you have done that already.) I assume the boiler is not weather compensated>

Off to work now so i will blab on more when i get home.

Cheers

ps: boiler temp adjustment is useful :rolleyes: nice of them to mark out temps

[Bigfreeze]

You can't remove the header tank without replacing it with something else. Its against regs for mains water to be sent to toilets etc. There must be a break tank installed. Also you've have no water if mains goes.

Don't know why you have an expansion tank at all. I can see no purpose on an open system with a gravity feed tank supplying the pressure. Although it is possible that the boiler/rads circuit is pressurised.

The tank will have one coil which the boiler water runs through and heats the tank. I'd imagine the 3 way valve is to divert flow either to rads or tank depending on demand.

[chillerman2006]

You can't remove the header tank without replacing it with something else. Its against regs for mains water to be sent to toilets etc. There must be a break tank installed. Also you've have no water if mains goes.

Don't know why you have an expansion tank at all. I can see no purpose on an open system with a gravity feed tank supplying the pressure.

The tank will have one coil which the boiler water runs through and heats the tank. I'd imagine the 3 way valve is to divert flow either to rads or tank depending on demand.

Evening BF

header tank will have to remain then, cheers

the expansion tank, would this be for the heating system

from what I can make of this, there are two seperated circuits

the hot water which is gravity fed and

the heating circuit which is sealed? and mains fed

without expansion tank, how is system pressure controlled ?

R's chillerman

[Bigfreeze]

Hi CM,

The water is gravity fed to the bottom of the hot water tank which pushes the hot water out the top of the tank and off to your taps. The boiler circuit is closed loop, circulating from the boiler to the rads or through coil in tank depending on demand. Pressure of 1-1.5 bar is fine here as the water going up will be balanced by the water on way down. The pressurisation is mainly to keep air out of the system, for rad performance and corrosion issues. The exp tank, as Mike said, should be tee'd in on the inlet side of the pump. I don't think any of this would affect your gas bills though

[chillerman2006]

Hi BF

thanx for the step by step mate, seems the setup is not as bad as first thought then, apart from need to move the exp tank and bring my temps down a bit, cheers

R's chillerman

[Bigfreeze]

No its fine, just messy looking. Had a look at the pics there. Can't make out if the arrow on the pump is pointing down or up. I assume its up, so then the exp tank would be better on otherside but not the end of the world either.

[MikeHolm]

Hi BF

thanx for the step by step mate, seems the setup is not as bad as first thought then, apart from need to move the exp tank and bring my temps down a bit, cheers

R's chillerman

Guys, we are talking about the same thing. I was pointing out that there is no need for an expansion tank and a gravity feed/expansion tank so get rid of one or the other.

The water feed i was talking about drops mains down to 1bar and is adjustable. Add an approved check valve and you won't lose your boiler water if the mains go down. Every boiler system in North america works this way. Use a proper sized exp tank and you can keep the water oxygen free for years so your rads will last a long time and there will be no need to bleed rads every year as some people need to do.

[MikeHolm]

No its fine, just messy looking. Had a look at the pics there. Can't make out if the arrow on the pump is pointing down or up. I assume its up, so then the exp tank would be better on otherside but not the end of the world either.

The problem with exp tanks with the port up is that sometimes air gets lodged in there and if the bladder doesn't stay wet, it doesn't last as long. That is why i keep them the other way around.

[chillerman2006]

Thanx Gents

will get a larger exp tank and mount up the other way and other side of pump, as there was loads of air in the system, pipes hammering for weeks, drove me mad, I presume I will get two tell tale signs if the bladder goes prior to moving/changing it, one being a pressure drop and two the outer wall will get hot to the touch, currently cool, all the info appreciated cheers

R's chillerman

[Bigfreeze]

Guys, we are talking about the same thing. I was pointing out that there is no need for an expansion tank and a gravity feed/expansion tank so get rid of one or the other.

The water feed i was talking about drops mains down to 1bar and is adjustable. Add an approved check valve and you won't lose your boiler water if the mains go down. Every boiler system in North america works this way. Use a proper sized exp tank and you can keep the water oxygen free for years so your rads will last a long time and there will be no need to bleed rads every year as some people need to do.

You need the header tank in this situation Mike as we have different regs in the UK and Ireland regarding mains water,than the US and Europe do

[MikeHolm]

BF, you have said that mains water is not allowed to go to toilets...what water goes to the toilets?

is the drawing below not allowed in the UK and Ireland?

7936

[Bigfreeze]

No, afaik you need a break tank. Basicly a tank 200-300L where the mains water is collected and then distributed to taps, showers, toilets etc by either gravity feed or pump. You only run mains to the kitchen sink (drinking water) and an outside tap.

[MikeHolm]

The above is the most common set up here. I wonder if it is only historical reasons for not allowing other methods because we are as paranoid about legionnaires and other issues as Europe and the UK are. Using your method, the volume of water per shower may be less but no one cared about that 50 years ago so I cannot see the benefit of the system.

[chillerman2006]

Hi MIke

Maybe it was just in case the mains water supply was lost, when I was kid I remember this was a quite common occurance...those without water tanks, knocking on neighbours for a kettle full for some rosey lea

Cant remember the last time this happened as so long ago, but if thats due to where I now live (modern supply network, old addresses in London was victorian, I think....I know the sewers still are) and newer installations are less prone to leaks or if it was a case of supply issues back then, no idea

R's chillerman

[MikeHolm]

Morning CM. Are you doing this on a mobile while pissing away your employers time? LOL Or is it lunch time and you are in the pub.:D

You are probably right about the historical stuff but I would think it would change by now. One benefit of the the lower pressure from the tank is less water consumption from showers. Toilets will fill slow tho. How do those toilets that work on 3 bar pressure to flush work in the UK?

[chillerman2006]

Hi Mike

back on track for you, as we swayed off subject slightly,

R's chillerman


It's my first EVAP, just a fan, TXV, sensors and coil. Everything else is indoors but i won't show that to you yet as the wiring sucks and I have to clean it up:D Take note BF.


Hi Mike

nice shiny black mate looks pretty and neat job

picture is decieving - is there an opening at the bottom for air intake

at first glanc it looked like it was sitting on the ground and balancing

on 6 inches of earth. haha my eyes, must be age catching me up

R's Chillerman


It is off the ground by about 24" for drainage and it's British racing green, being a 60's BRM and Lotus fan, I thought that appropriate. Quiet as a church mouse. I was wondering if anyone would say anything....except for mumbling "what a pile of shyte":D


now you say it, my eyes can see its brg

whats 'brm' ?

and now my turn for the questions, with a cooling system you select the evap for required work

then add compressor/condensor/txv to match

How do you design a heat pump ?

Do you start with the condensor and then match components ?

R's chillerman


Did you make the coil yourself or did you buy it?


BRM was British Racing Motors who made some great racers in the 50s and 60s and Lotus is....well....Lotus.

I had a comp from a 12kw (give or take) heat pump that someone smashed up badly. it is a ZP40 and the only other good thing in it was the TXV and a couple of pressure switches. That was my starting point and the house is not too large so it may be a reasonable fit.

I used the least scientific method available to determine the coil, I added up the tubing surface area of the busted up wrap around (standard north american type) and the aluminum fin surface area and the volume of the tubing and using all the discussions with all you guys and a s**tload of research, I drew up the coil and had it made by a local establishment. I'll look for a coil end photo to post but I basically wanted a horizontal coil which appears to be the best for defrosting. The coil is 30" by 60", 4 row, 2 evenly split runs.

It will still take me a long time to get used to things like coolpacks so I didn't rely on it for anything although I tried. I don't know enough yet to use it with any certainty.

I picked 40C as my target temp for the buffer (450L, UFH and no dhw). I used the SWEP design software for the condenser (which I think may be a little bit small, but we will see as the year goes on) and I have bought lots of Hx from them before so I like the product. I cheated in that I didn't have to size a TXV (assuming my evap is sized right) so we will have to see how it runs, so far so good.

Real seat of the pants flying.


Hi Mike

your method appears logical mate

you have evap/comp/txv already matched, replaced evap with equal volume evap

then matched condensor to system, an half educated thought would be on setup

you will need to balance the system by air flow across evap and suction superheat/mass flow

to get your desired condensor temp but taking into account compressor protection

nice one mate, design is way beyond me now but maybe one day :)


R's chillerman


Thanks CM, I know my liquid fluid flow quite well but I'm still a novice in the "art" of refrigeration so it is actually a big step for me (old hat for many here I suspect)


Nicely done Mike. You'll have good defrost draining from that design and protection from snow. Also the height of the ground and lack of legs makes a back build of ice also impossible. Good work mate.

If only I could progress my own projects as quickly:o


Where is the fan, is this induced draft or forced draft.?
The does the air blow up out of the evap or down out of the evap?


Mike, this now explains why you are difficult to find. Goober, just keep that office chair polished ;) and think about the fun you are missing out on by not being on the tools :p..Mike.


7900
It had just finished raining so it looks wet. it is an updraft VSD unit. I haven't gotten to insulating the piping when i took the pic but it's done now.


All this will put me in the poor house for sure but it is great fun. I love the challenge.


Lets look at this as a purist
We do we want for efficiency, the highest possible air entering temperature, and air that is easiest to move.
So ,looking at the picture we can see that we are in fact pulling the coldest possible air (from the ground and recirculated air) into the evap coil, and driving air against its natural tendency to fall. air will fall naturally out of the evap coil.


The air movement as you state will be working against nature so I suspect the electrical draw might be a little bit higher but given the current draw I doubt it will be much. I haven't seen any heat pumps here that would be a downdraft because they are almost the units are offshoots of AC units.

The ground temp at the house will be a few deg warmer than the ground 1m away from the house because it is not that well insulated. I had contemplated having the heat recovery exhaust exit the house under the unit or even within the box but it was technically difficult to do.

If your air on and air off temps are only a few deg different and given the heat loss of the building at ground level (there is a full basement), I'm not sure that it will be an issue. 25 years ago we regularly had temps of -25 in the depths of the winter but the last few winters I can count very nights below -15C with most at -5 to -10. I use -15 as a goal which is why I was interested in the digital scrolls performance.


Mad, what do you think the performance change would be if the the fan was removed from the picture?


What yo have built is an excellent cond, (and this is what everybody does, even in this application)
Here NZ the ground temp in the morning can be a good 6C below air temp,
So for example if the fan where underneath, drawing air downwards and discharging along the ground, it is possible that the SST could be 6C higher (in the above case), that could increase duty by close to 15%.
(off the top of my head)


Food for thought, as they say, I will have to look up norms but local temps (local meaning within a 1m or so) are very influenced by what is around them. Is the wasted heat through the wall of the house going to influence the air on temp when the coil is 600mm above the ground. I have never seen a study on this but I am sure it exists....somewhere


I'd have to disagree with you there Mad. There would be almost no difference in the air temp a 300mm off the ground and that off air 1.3m off the ground. I would say almost none tbh. The disadvantage of downdraft in Mikes design is that it could encourage short cycling of air, which would be much worse than any potential gain.


Even tho it is 600mm off the ground and has free air on 3 sides? Maybe i am not getting the meaning of short cycling correct...


The comment is not particular to this evap, The air is drawn past the ground to enter the evap, hence must be colder, the air exiting is colder and more dense than the ambient so will fall to low level, encouraging short cycling.
Many other factors do need to be considered exiting air velocity, free area in which it is to be mounted.
Not to say that you would just mount the fan underneath.


Here is the next Evap I had in mind,
7921

In the winter The solar panels are often unable to reach the temp needed to help the DHW tank but does contain enough heat to add to the evap. The question is, at what sustained temp would the coil be considered to be overheated? 40C? Assume 410A. Probably not enough info;) typical eh...

[chillerman2006]

Morning CM. Are you doing this on a mobile while pissing away your employers time? LOL Or is it lunch time and you are in the pub.:D

You are probably right about the historical stuff but I would think it would change by now. One benefit of the the lower pressure from the tank is less water consumption from showers. Toilets will fill slow tho. How do those toilets that work on 3 bar pressure to flush work in the UK?

Hi Mike

Mobile Internet (HSDPA) 2mb connection, pukka, can work and play at the same time

R's chillerman

[MikeHolm]

Pulling a vacuum eh? bored?

Still looking for thoughts on a combined coil? I don't know if there are any other combi coils there (boiler or other options)

[chillerman2006]

Hi Mike

when in defrost, I presume the fan is off ?

would it be worth insulating the box the evap sits in ?

also you are going for an angled evap this time, whats the benefit here ?

R's chillerman

(maintenance - get 8 hours for what takes me max 4)

[MikeHolm]

Yes, the fan is off for defrost, I may use hot solar heated water when available to defrost but we will see. The angled coil will aid in getting rid of liquid during defrost and it means I can mount the unit between the houses when there is only 1.8m of space, without pissing off the neighbour.

[chillerman2006]

Hi Mike

many ventures all in one here, mate, certainly keep you busy and hopefully fat wallet when finalised

another gremlin you have which warmer climates dont suffer is a drop in specific heat transfer

if looking at -20*c .... glycol mix needs to be to -30*c ..... which I think is roughly 50/50

cp of water is 4.18 where glycol is 2.36 ....... lowering efficiency of the already lower temps, heat transfer

was thinking too that maybe during winter you often get clear skys and low sun as we do here, making your solar systems more available for work, but 'think' I recall you saying panels require +15*c to work well and winter sun is not as strong

certainly got your work cut out here mate, finding the right balance of heat/energy/heat

R's chillerman

Argh ! A thought - what about magnification of the sun onto solar ?

[MikeHolm]

Nope, the normal hot water panels I use produce good heat in -15C -20C as long as it is sunny, which it often is in the winter but i may only get 30C from the panels and not 70-80C that i would like.

Water/Glycol is 60/40 typical. There are additives that help the freeze/boil characteristics somewhat but you are right, transfer is not great. We are used to it in this business as there is not a lot of option except for system that drainback the water to an inside storage tank when not in use.

All in all, solar does work well but financially, not unless you have some subsidy as you have.

[chillerman2006]

Hi Mike

thats good, got my +/- round wrong way

you can start fires with a magnifying glass, is this something that can be used to increase heat

or is this something that is already part of a solar panel (built in)

seems strange how some western countries subsidise some products and not others

R's chillerman

[MikeHolm]

I had a lot of t-stat and pump wiring to do before I started up the HP. Yesterday started it up for the first time with a floor heating load, got very high pressures for the first couple of minutes (tank was cold too???) then it settled down but pressure is getting near 400psi at 40C water temp and TXV is hunting a bit. I think I will put in a receiver tank if it will help the hunting issue. I really want something to keep the the pressure from passing the 400psi mark but I'm not sure what the best method should be...any ideas?

superheat is running between 15-16F with a cold tank and 6F when it is near setpoint. DT on the water side in and out of the tank is about 4-5F

[chillerman2006]

Hi Mike

if valve hunting, first confirm you have liquid feed by taking discharge pressure and convert to saturated temp, then check you have a lower temp on liquid line, if sure you have liquid feed then its just a case of getting the valve set up right

you can increase discharge temp by increasing suction superheat, this will then give you a higher discharge temp at a lower pressure but on the flip side higher suction superheat will reduce mass and compressor work is increased to move the same mass ...

what refrigerant are you using ? R410a for instance has high pressures but lower temp to pressure than other common refrigerants

400psi is 27.2 bar which if R410a is fine

R's chillerman

[MikeHolm]

Thanks CM, I will look at it again during the week.

[Bigfreeze]

Ignore the fact you have low discharge temps from cold. Its always the case when starting a heat pump. Only when the floors return water temp is 20C plus can you really zero in on whats happening in the fridge circuit.

Starting the machine in cold weather you should actually help your discharge temps by slowing the pump speed until return is about 20C.

What gas are you running. 407C i assume? 400psi is pretty high in that case. What are your inlet outlet temps across HX on water side?

I would install a receiver. Just to give yourself a bit of leeway when it comes to refrigerant charge.

[MikeHolm]

HI BF, it is a 410 machine but I will have to go back and take measurements tomorrow. Problem is that I am only running on stage one as i haven't put a 2nd stage switch on it yet and I am wondering what the best way would be to do that. Like I said above, I'm getting 10.5A @230VAC on stage one and this seems a bit high to me.

[Bigfreeze]

HI BF, it is a 410 machine but I will have to go back and take measurements tomorrow. Problem is that I am only running on stage one as i haven't put a 2nd stage switch on it yet and I am wondering what the best way would be to do that. Like I said above, I'm getting 10.5A @230VAC on stage one and this seems a bit high to me.

If its 410a then you're not a million miles out at 400psi. Your condensing temp should be about the same as your outlet temp give or take a degree or two. 400psi would be about 47C condensing.

Dual stage? As in two compressors? I assume they're two 7kw units. If so, again you're not a million miles away assuming that that figure includes the fan motor and the fact you're running up towards 50C.

Are you running a seperate coil for each compressor?

[MikeHolm]

It is a ZPS two stage copeland,

8195

8196

On full output it should pull 9.4A at 10C evaporating and 40 condensing and I will check what pressures we are running today, but last i checked, I was drawing more power than that and i hadn't reached a 40C tank temp yet.

[Bigfreeze]

Are you sure its evaporating at 10C. That would be high for this time of year. 0C would be more likely. According to the weather service its 11C in Toronto today, so no way its evaporating a 10C. 3C maybe.

[MikeHolm]

I stand corrected, I meant that ambient was 10C. I haven't been down to the job today as they are finishing the wood stairs and I can't get in the basement. I will see tomorrow.

[MikeHolm]

OK, the R410A HP seemed to be running well enough while the weather was a bit warmer. What bugged me most was the high current draw 15.5A when the data sheet says it should be 10.5A.

I put on the gauges and I get suction 4.72Bar, -10C,
discharge is 28 Bar, 48.3C
Liquid from the buffer is 49C and out is 53C

air on 9C and off is about 5C (comp stopped as it was going down and I was about to take pipe measurements on the evap) and the sun went down anyway.

I was going over in the morning and when I got there the EVAP was a solid block of ice.

I think it is overcharged but I have a feeling there is something else as well (perhaps condenser is too small). Any thoughts?

[Bigfreeze]

OK, the R410A HP seemed to be running well enough while the weather was a bit warmer. What bugged me most was the high current draw 15.5A when the data sheet says it should be 10.5A.

I put on the gauges and I get suction 4.72Bar, -10C,
discharge is 28 Bar, 48.3C
Liquid from the buffer is 49C and out is 53C

air on 9C and off is about 5C (comp stopped as it was going down and I was about to take pipe measurements on the evap) and the sun went down anyway.

I was going over in the morning and when I got there the EVAP was a solid block of ice.

I think it is overcharged but I have a feeling there is something else as well (perhaps condenser is too small). Any thoughts?

I'd definitely expect that kind of ampage draw on that size compressor with that much differential between low and high side. Try to keep the outlet temp down to 45C if possible. Running at high temps in heating mode will write off your compressor in a short space of time.

Could well be overcharged as your condensing temp and water outlet temp should be within 1C of one another and right now they're 4-5C apart. Your subcooling should be close to your return temp too.

Whats controling defrost and what type of defrost is it?

[MikeHolm]

That's the problem, it is a York board with defrost built in. The manual gives no indication except that there are jumpers across pins depending on the size of unit. I assume that is for defrost time. There is a bonnet sensor, defrost sensor as well an ambient sensor.

I assume it just triggers the reversing valve.

It also mentions something called "Hot heat pump" but does not define what that means.

Bugger....

The above temp is the highest the unit gets to as my tank setpoint is 49C

[mad fridgie]

I would say cond side is very good, suction does seem very low for that ambient and condensing pressure.
(when dealing with temps and pressure which are very close, you may just find it is the accuracy of the instruments that you are using.)
The amps are spot on, for those conditions.
You need to work out why your suction is so low, at 9C and high SCT you should be well above freezing.
Do you have sight glass in the liquid line?
what is suction return temperature at the comp inlet.

[MikeHolm]

Suction return about 6" from the inlet was -10C.

I am thinking of putting in a bigger pump to get a bit more out of the condenser. What do you think?

As BF says try to narrow the gap some....I thought the condenser was a bit small

[MikeHolm]

Unfortunately there is no sight glass, my next concoction will have one

[mad fridgie]

Your SCT is 48.3C and water onto the cond is 49C, can not any better than that! (well that is actually impossible)

[mad fridgie]

I would say that you either a coil design problem or not enough airflow (my guess)
What is your air onto the coil temp, not ambient

[MikeHolm]

Tomorrow I will put the digi-cools on and take a pic under the conditions. It is supposed to be 10C out tomorrow. I cannot decide if I need more gas or a bit less.
I still don't like the elevated current draw. Not that efficient really...

The defrost is really worrying me but it must just be an electrical setting.

[MikeHolm]

They are about equal, within .5 deg

[Bigfreeze]

Your SCT is 48.3C and water onto the cond is 49C, can not any better than that! (well that is actually impossible)

He's condensing at 48.3C which should be equal to outlet temp. Subcooled temp would be lower. Closer to return temp. At the moment his condensing temp is equal to his return temp, which is too low.

Check your super heat. Should be floating around 3-4K.

[mad fridgie]

The outlet temp can be higher than SCT, I would say there is a slight error in the readings.
But there is nothing wrong with side.
The low SST is the issue.
With -10C suction temp. nothing wrong with charge.

[MikeHolm]

I can't get the bloody thing to defrost and I can't get to the entire coil to do it with hot water (design improvement #1 coming up). Luckly it will be 14C tomorrow. I can't ever remember having these temps at this time of the year.
New reading shortly

[MikeHolm]

Here are a couple of pics that should tell a tale. EVAP Air on is 11.7C air off is 5.7. SH stayed steady around 7-8C, SC started off around -6-7C and by the end was around -17. The biggest issue is the Dt measured right at the discharge and 6cm from the suction, 55C by the time it reached limit. My 450L tank was to be heated from 20 to 39C. It took 50min...too long.

833583368337

I was keeping a 2-3C differential on the liquid side of the condenser.

[MikeHolm]

I was looking at the high subcooling, reasonable superheat and thought i might have a bit of a high charge (I thought there might be some backup into the condenser) but not too high. So I took a bit out, and i didn't have a scale but it was a couple of seconds on vapour side. Now my SC goes as high as 30 deg and SH is down to around 4 deg. The rest of the above conditions are roughly the same.

Could I be looking at a liquid line restriction?

[mad fridgie]

Mike not enough info.
Forget what you are using for just for a moment
So what info do we need
Water entering the condenser
Water leaving the condenser
Flow rate if possible
Air temp entering the evap (not ambient)
Air temp leaving the evap.
saturated suction temperature ( SST) pressure/temp relationship
refrigerant temp leaving the evap
refrig temp entering the compressor
Saturated discharge temperature (SCT) pressure/temp relationship (at the comp)
Discharge Temperature (just after the comp outlet)
Liquid temp leaving the condenser
Liquid entering the TEV
Liquid Pressure ( at the TEV inlet if possible)
Current draw of the compressor

[mikeref]

This seems to be beyond me as i need to actually SEE this working to do any figuring. However if i may put my 2 cents worth in, could your evaporator have too closely spaced fins for those temperatures? Maybe the depth of your evaporator is allowing too much T.D. As we all know, once ice forms, it continues to grow and insulates evaporators, reducing performance and reducing air velocity.

[MikeHolm]

Mike not enough info.
Forget what you are using for just for a moment
So what info do we need
Water entering the condenser
Water leaving the condenser
Flow rate if possible
Air temp entering the evap (not ambient)
Air temp leaving the evap.
saturated suction temperature ( SST) pressure/temp relationship
refrigerant temp leaving the evap
refrig temp entering the compressor
Saturated discharge temperature (SCT) pressure/temp relationship (at the comp)
Discharge Temperature (just after the comp outlet)
Liquid temp leaving the condenser
Liquid entering the TEV
Liquid Pressure ( at the TEV inlet if possible)
Current draw of the compressor

Mad, I can get all that again with exception of the pressure at the EVAP( the pressure tap is within 1.5m of the tev). Excuse my ignorance but I assume SST or SCT includes the SH or SC. They should just record the suction temp and discharge temp separately.

My biggest fear is causing damage to the comp in the short term with such a high pressure differential (20bar).

[MikeHolm]

This seems to be beyond me as i need to actually SEE this working to do any figuring. However if i may put my 2 cents worth in, could your evaporator have too closely spaced fins for those temperatures? Maybe the depth of your evaporator is allowing too much T.D. As we all know, once ice forms, it continues to grow and insulates evaporators, reducing performance and reducing air velocity.

Mike, the coil designer has a lot of experience with heat pumps and long before I came to him for this coil, we talked a bit about how he designs his coils. He would rather have a larger spacing than have a tight package. There is a problem with defrost on this unit but I think it is electrical in nature. The coil is a 5 row and I will post a pic of the tube arrangement when I can find it.

[mad fridgie]

"SST and SCT" are in other words "Te & Tc", or the gauge pressure converted into a temperature. They are not subcooling or superheat
Example R410a 20Barg = 35C, if this was the discharge pressure then SCT would be 35C, not to be confused with discharge temperature, or liquid pressure or liquid temperature.

[mad fridgie]

What size tube are using in the evap coil and how many circuits are there?

[MikeHolm]

Hi Mad,
Here is a pic of a similar coil. The liquid line should be in front of the discharge line facing in the same direction (up). All tubing is 0.5" od and there are 4 circuits coming to a common 1.375" manifold which you can see in the pic. The overall coil size is 30" by 48" long. The tube rows are 1" apart and the U bends are 1.25' on centre.

According the the pic I posted above, what the digi-cools show is the SST (0C) and SCT (46C). I'm still getting used to everything.

8340
Disregard the ends that you can see at the corners. It is not quite the same coil

[MikeHolm]

Well, my issues with defrost were all down to an improperly grounded RV wire from the defrost control. whenever the control wanted to go into defrost, that wire went to ground and the valve didn't move. All seems well now.

[Bigfreeze]

Thats a weight off your mind. Not sorry to put that to bed I'm sure

[MikeHolm]

Yes, well...on to the next thing which is programming a control that will do everything needed in one product. I am being pushed by Jens (the old Dane HP builder) to use the TAC Xenta controller and control all pumps, mixing valves and fans. I don't know if there is a difference between this type of controller and and equivalent PLC from Siemens or Allen Bradley. Any idea? As we have seen with most of the package North American stuff, it still uses 30 year old control technology and it can be improved on.

[Bigfreeze]

Whats wrong with the Lodam? Have you hooked it up to your own unit yet?
Better interface and more complete solution for your purpose than the other products I think

[MikeHolm]

The problem with the Lodam is that it is not capable of controlling many different loads other than the Heat pump itself. For example, I would like to be able to have a back up electric element which i can schedule based on off peak power rates. i also would like to be able to program the HP cycling and motorized mixing valve positions to blend water from a storage tank or solar to the evap. I don't think most of this is available with the Lodam.

I haven't installed it on a HP yet but I will over the winter. I have 5 Viessmann boilers and a number of solar systems to install first. .... where does the time go?

[Magoo]

Hi Mike H.
have you concidered a small micro PLC they are realtively cheap these days, come with analogue and digital inputs/outputs. Then set up the whole lot to what you want

[MikeHolm]

Howdy Mr Magoo,
I have thought of that and before I decide I was told that the TAC Xenta was different than a standard PLC and there are cost savings as some of the output output relays are included BUT I haven't been able to find a good comparison guide between the different products. Once I get a system going, I 'd like to stick with it.

[MikeHolm]

The bugger went off on a LOW pressure lock out. I wasn't there to see it but that is the fault code. First thing I will do is to get a low pressure timer so the switch has to stay open for a period of time before the lockout occurs. Odd thing is that it hasn't been very cold the last few weeks (-3 to +6) so I don't think it is weather related.

I will also get a receiver for it. It has about 5.5kg of refrigerant in so I should get a receiver to hold that charge, is this correct? Also, any idea what time is reasonable for LP switch timer 1m, 2m ,5m?

[Bigfreeze]

I wouldn't hold out the LP switch for more than 20secs. If it staying in low pressure for longer than that its there for a reason. How high or low is the switch set. About 3-3.5 bar would be about right on a 410a system.

[MikeHolm]

I'm not sure what the rating is for the LP switch but the control allows 4 soft lockouts (of 5 sec each)then makes a hard lockout which needs to be manually reset. This appears to be what happened.

[paceinternet]

A couple of months have gone by now Mike. Any more interesting experiences with the system to share?

[MikeHolm]

Well, now that you have mentioned it....a lot has happened. I decided to use the stock York board for archery target practice and get the TAC control put in. It seems the lockouts I had were partally due to the board not accepting one or the other stage turning off without the other one. Seems I cannot make it work so out it comes and in with the new control. Stay tuned.

[MikeHolm]

Long day yesterday. FINALLY got a control on my ASHP and charged up the system, but it is only for cooling right now. It is TAC because we had a few 301s and the old man knows them well enough. The problem is, he always had someone to do the programming and it seems the changes since Schneider bought them, results in no access t the proprietary cable for downloading the programming so the one we put in will now do cooling only as there is no defrost function fitted (it was meant for GSHP). Still looking for the right control. Lodam is a nice control but has its limitations, defo better for replacement or standard setups rather than original designs tho.

Anyway, It is running very nicely but our evap is a bit big for this system (we dropped the comp to 8kw from 10kw) but should do quite well in heat mode.