PDA

View Full Version : High Wall up and down



mad fridgie
16-10-2009, 10:14 AM
In NZ floor consols are very expensive (can be almost twice that of a comparable high wall heat pump)
I fundementally disagree with high walls for heating.
(cooling great)
Should we fit high walls at low level? (150-200 mm from the floor)
Reasons for or against?

Yuri B.
16-10-2009, 02:29 PM
Hello Mad Fridge.
I may be wrong about the exact place but I believe homes in Australia need more cooling than heating throughout the year. Floor units are probably more expensive because they are less popular (hence rare, what allows vendors to ask more for them) - for the above reason.


Should we fit high walls at low level?
In such case when cooling season comes someone will wish to drag them up to the ceiling.
I would be installing the high wall ones there where they are intended to be and played only with air flows (heating downwards, cooling horizontally).

mad fridgie
16-10-2009, 08:25 PM
Hi Yuri, In Australia, yes you need cooling, in New Zealand (I am in the south Island we need heating and very little cooling)
Just you let you know I (we) have fitted nearly 5000 high wall units at low level. This does cause some arguments in the industry.
Some manufacturers void the warranty and others do not.

momo
21-10-2009, 01:43 AM
Regulations in Spain suggest that naturally occuring layering of air by temperature should be made use of. What good is it to cool above 2mts (5') from the ground where we walk and live? So let us concentrate on cooling and heating what is used. I have applied this domestically and for heating it works well avoiding the "cold feet" problem. For cooling: the cooler air tends to lie at up to about 1m50cm (good for office work height) but that is dependant on air flows in the room. Manufacturers (Mitsi, General, Daikin...) charge a heavy premium on these units well in excess of the additional cost of a second fan and outlet etc. The problems I see with using normal wall mounts is they are more easy to damage and difficult to access; and will be "adjusted" to control tempèratures associated with height (some ceiling/low wall units have a switch to set according to use.) The angle of the airflows will not be ideal if placed too near the floor and can re-circulate. (Shows that some ideas travel throough the world like cosmic rays! ;-) )

mad fridgie
21-10-2009, 03:36 AM
Hi Momo, you are right about the airflow, To save any issues we disconnect the swing motor (client dependent) set the parrallel with the floor (a small amount silicon to hold in place), no recirc at all.
On cooling when we occasionally need it, if the roomis unoccupied for a while the air does stratify quite cool at floor level. Never actually had a complaint on the cooling side.
As far as damage it would "seem" to be a problem, but never seen it as an actual problem. (did see a damaged one up high, they hung the clothes, with a hanger of the rips on the outer case, yes they snapped off)
I believe that mounted high walls down low for heating, they are between 30-50% cheaper to run. Some fundemental science and lower set points because your feet are warm.
I feel those cosmic rays!!!!!!

cadillackid
25-10-2009, 02:49 AM
often the reason with wall splits mounted low that you "feel" warmer is that in effect the unit is Overshooting your desired temperature...
wall splits mounted high often have programming in them that if you set the temperature at 72f it will heat at the unit to say 75 or 76 or sometimes higher depending on the design before it reduces or shuts down...

this is for a couple reasons... one that most times in heat the indoor fan shuts down and these is residual heat on the coil and in the plastic cabinet (most wall splits the temp sensor is located on the intake part of the coil so it stays warm longer than the room)...

also the temp sensor takes into account it is warmer up higher so the occupants of the room feel just fine and close to setpoint temp at occupant level..

mounting wall splits low usually results in the actual room temperature at occupant level being above the setpoint by a few degrees so obviously they feel warmer......
-Christopher

Magoo
25-10-2009, 02:57 AM
mad frigdie.
have any of your suppliers given an actual real logical reason for not mounting them at low level. Interesting as to why. Could it be that all the geeks are outside their comfort zone, and reason is not in the manual. ( cover ar#e mode ) Good on you for thinking outside the circle for your clients sake.

martin

mad fridgie
25-10-2009, 07:38 AM
often the reason with wall splits mounted low that you "feel" warmer is that in effect the unit is Overshooting your desired temperature...
wall splits mounted high often have programming in them that if you set the temperature at 72f it will heat at the unit to say 75 or 76 or sometimes higher depending on the design before it reduces or shuts down...

this is for a couple reasons... one that most times in heat the indoor fan shuts down and these is residual heat on the coil and in the plastic cabinet (most wall splits the temp sensor is located on the intake part of the coil so it stays warm longer than the room)...

also the temp sensor takes into account it is warmer up higher so the occupants of the room feel just fine and close to setpoint temp at occupant level..

mounting wall splits low usually results in the actual room temperature at occupant level being above the setpoint by a few degrees so obviously they feel warmer......
-Christopher

How true, some units the off set is as high as 5C (8F) We tend to find that to be comfortable we set to late teens.
Of course this off set actually affects the discharge pressure (as the air on in not really 20C, as per test data) So efficiency is never as good as therory would suggest. In NZ the houses are not thta well insulated, so you tend to find on the cold days that units up high are set very high, just to get the heat to a low level. (Cold feet)

mad frigdie.
have any of your suppliers given an actual real logical reason for not mounting them at low level. Interesting as to why. Could it be that all the geeks are outside their comfort zone, and reason is not in the manual. ( cover ar#e mode ) Good on you for thinking outside the circle for your clients sake.

martin
Logical reasons for not putting down low.
Cooling does not work as well (I agree with this point)
The biggest reason is "Because they always go up high"
We will not warrant them.
The filter will get dirty quicker. (no difference)
Increase in Asthma. (blowing all the dirt of the floor)
An animal my pee on it.
Air will short cycle. (yes you need to ensure that the air runs parrell with the floor, actually the air is laminar flow and actually draws a vacuum "venturi effect" and draws air away from the unit
looks ungly (well they all do!)
The electronic eye does not work (i can agree but would not even consider these units)
Kids will spill drinks into it.
Set point is wrong (I agree,you set the remote a little cooler).
So really no one has ever come up with a tech reason for not putting them down.
What are the real problems!
When positioning ensure you do not have the air blowing directly at the seating. (when the unit stops or goes on a defrost they tend to feel a cold draft when in fact they are actually missing the heat!
If you have spilled or have a remnence of carpet cleaning fliuid, you can get a dark mark "drop" (in the carpet cleaning industry) where the air blows.
Apart from that they are great, for heating I have no problem sizing 30% small in comparrision to a unit mounted high.

cadillackid
25-10-2009, 07:53 PM
I built mine into the existing Zoned system in my house and they work like a champ...

built my own coil boxes... they hang in the basement.. the central variable speed blower assures proper air over the coils and the computer control does its job well... that way I have the benefits of multi-zone inverters without those ugly units on the wall..
-Christopher

back2space
26-10-2009, 12:41 AM
I built mine into the existing Zoned system in my house and they work like a champ...

built my own coil boxes... they hang in the basement.. the central variable speed blower assures proper air over the coils and the computer control does its job well... that way I have the benefits of multi-zone inverters without those ugly units on the wall..
-Christopher

Wouldbe interesting to see some pics mate.

Magoo
26-10-2009, 01:41 AM
Mad Fridgie,
have you considered developing your own console unit using the hi wall coil system and controls.

mad fridgie
26-10-2009, 02:17 AM
Mad Fridgie,
have you considered developing your own console unit using the hi wall coil system and controls.
We did work heavily with Toshiba and Carrier, and asked about a simple change in the electronic (a toogle switch for uphigh or low down operation, adjusting the off sets and louve positioning) Also asked to change the plastic outer case, just for looks. (that just about applies to all of the units, dare i say some of LG models look the best)
The market is to small in NZ was simply the answer, they felt that there was NO tech issues with mounting low for primary heating.
I moved out of this market about 4 years ago, it has be come to flooded with sparkies who do the job for nothing.
The reason I bought this up was due to a govt depts new NZ policy. I friend of mine who also mounts low has been asked to re-install, why, an archietects mother had one installed, she loves it (refuses to have it moved) he insists because it is called a high wall. The govt dept have directed that they must go up high and the contractors can not recommend it at all. I call this bueracratic BS
I can say the number of complaints from down low to those compared to up high is almost zero.

cadillackid
26-10-2009, 02:00 PM
here ya go guys... I have some pics.. hopefully you can see them through my web portal... im still working this system so not 100% is finished but gives you an idea what i have been working on...

here is a couple of one of the coil boxes as I was building it and test fitting... the coil sits diagonally in the box.. these coils are designed for low velocity air... as you can see with a multi-fold coil there is a huge amount of coil area... on the mini split air is brought over the coil at low velocity and then turned to high velocity at the outlet... I have allowed for twice the airflow Size as the coil is diagonal and I want to keep a slow flow in the box... of courtse I dont push near as much air across it as the sizing of the hole in my box would suggest.. but it keeps turbulence down since I am causing the air to "turn".. and it works.. i have even temperatures across the whole coil..

http://www.cadillackid.com/images/hvac/coilbox1.jpg

http://www.cadillackid.com/images/hvac/coilbox2.jpg

http://www.cadillackid.com/images/hvac/coilbox3.jpg


and here is one of the unit boxes hung from the ceiling and installed... I had one running all summer and now fall.. these 2 are just recently put in and so I havent hooked up the drains yet.. dont need it for heating..

http://www.cadillackid.com/images/hvac/unit2.jpg

http://www.cadillackid.com/images/hvac/unit3.jpg


and now here is my prototype control interface board that I have made.. the unit's original indoor and outdoor control boards still control the compressor and such.. my board just sends these units several things..
1] it sends the unit its mode and temperature to run in.. I only use heat, cool, off.. I dont use any of the other modes..

2] it sets the unit always to "auto fan" even though its fan motor is not connected.. this allows me to see what the unit is 'thinking' as far as airflow.. so i can adjust my dampers and blower speed accordingly..

3] I "force feed" the unit's on board thermistor input whatever value I so choose... since these units are designed high wall mount I offset the temperatures and then send a 0-5 volt signal to it...

4] this is possible because these chigo units had an included wired controller so I had a hard wire 2 way interface to work with... I simply cracked the protocol and talk to it with my board..

5] my board then interfaces to my host PC... in the event of PC comm failures or over-temp conditions it can shut the unit box down... I have 3 temp sensors on board that measure.. coil inlet, coil outlet, and Leaving air temp...

http://www.cadillackid.com/images/hvac/unit2control.jpg


dont worry these are only prototype breadboards.. and no more than 10 volts DC anywhere on them.. after I know all the inputs and outputs I need are there.. ill make them real boards in real cases...

http://www.cadillackid.com/images/hvac/unit3control.jpg


here is the central gas furnace and blower i use to push air over these things... it has been outfitted with a MODBUS networked dual triac variable speed controller... Ive had the zoned system before I did the individual units.. ive been running this blower controller for 4 years now with no issues.. since it drives the primary AND aux windings off phase.. there is no motor buzz and it stays cool even at low air flows..

this is also my "AUX" heat.. since it is a 95% AFUE model.. ill likely only run the heatpumps down to about 35 degrees outdoor temperature (depending on humidity)...

this furnace also has modulating gas in it so that it can keep stack temperatures and supply air temps low during low load periods... this unit was my sole source of heat for the last 4 years.

http://www.cadillackid.com/images/hvac/gasfurnace.jpg


here is my economizer / fresh air intake.. this allows me to push 500 CFM of air from the outside into the system if I want "free cooling".. and filtered air without conditioning... it has a sure-seal damper on it.. so I can keep it closed.. open damper.. or select one of 2 speeds for the injection blower...

http://www.cadillackid.com/images/hvac/econ.jpg


and finally here is my diagnostic screen that I use to watch and adjust parameters on the new system...

http://www.cadillackid.com/images/hvac/hvacdiags.jpg


thats the system in a small nutshell... there is lots more to it.. but gives you an idea where i am going here..
-Christopher

mad fridgie
26-10-2009, 07:26 PM
Nice Effort, certainally some work gone into this project

back2space
26-10-2009, 09:24 PM
Looks great mate, your basement turned
into a dedicated plant room. How does the
conditioned air get to the rooms? Are they ducted?

cadillackid
26-10-2009, 10:13 PM
there are short runs of flex duct going from the boxes to the rooms...between 6 and 10 feet per run and mostly straight... im not big on flex duct but it seems everyone uses it these days and I guess its ok for shorter runs....

the house has returns in each bedroom and in the greatroom.. returns are high supply is low... the outlets are in the floors...

pretty standard duct setup for newer homes in the USA with basements....

I once worked on a system with a friend of mine where we reversed supply and return for summer and winter... and amazingly enough it really didnt seem to make a lot of difference for cooling.... when we played around and heated high and returned low it always felt cold... it always felt warm if we heated low and returned high..

in summer the ony difference of note was that when supplying high we felt more air blowing on us....

so my guess is thats why most homes are built supply low and return high....

I also left it so i can pull the end caps off of each box if i need to clean the drain or service the coil...... although those coils from china look to me to be pretty much throw-aways if they leak... Ive got them supported well and they are lightweight so I dont expect leaks....

these units are rated so that the outdoor unit could be located up to 5 meters above or below the indoor unit.. ive got less than 1 meter of total vertical traversal in the linesets....

they are rated at 7.5m of lineset with up to 6 90's... ive got 7.5m lineset with 1 or 2 90's.. and they are very wide 90's.. I like to keep linesets as straight as possible...

ive just always wondered about inverter splits and oil return with the evaporator below the compressor but many are installed this way and run fine...

just seems since they run at lower capacity most of the time the refrigerant velocity to pick up oil isnt there but they must do something im not aware of....
-Christopher

Gary
26-10-2009, 11:52 PM
ive just always wondered about inverter splits and oil return with the evaporator below the compressor but many are installed this way and run fine...

just seems since they run at lower capacity most of the time the refrigerant velocity to pick up oil isnt there but they must do something im not aware of....


I had understood that the whole point of inverters is to maintain constant capacity... am I wrong about this?

Magoo
27-10-2009, 12:05 AM
Mad Frigdie.
I can appreciate why you have given up with H/P market as everyman and his dog installing them. None of them can do a heat load calculation and only sell on price. Up here we have got plumbers installing them.
Several calls from disatisfied owners, saying that they are still cold and power account gone out the window. Plus a lot of complaints about these heat vent and condensation systems.
Remember NZ is the home of burocrats

cadillackid
27-10-2009, 01:47 AM
gary: inverters can vary their capacity for the conditions... which makes them nice because you can easier size them up.. plus they can adapt for temporary loads.. say conference rooms where you have large and small crowds..

in my case at my house i like to open the windows and then the house gets real hot and my old system took forever to cool it down... this one will give me quick cooling I need plus then it will vary itself down and run for light loads...
-Christopher

Gary
27-10-2009, 02:17 AM
gary: inverters can vary their capacity for the conditions... which makes them nice because you can easier size them up.. plus they can adapt for temporary loads.. say conference rooms where you have large and small crowds..

in my case at my house i like to open the windows and then the house gets real hot and my old system took forever to cool it down... this one will give me quick cooling I need plus then it will vary itself down and run for light loads...
-Christopher

I have little experience with inverters, so I may be wrong on this. As I understand it:

Under light load, the refrigerant is less dense, thus the mass flow/capacity tends to drop (underload). The compressor then speeds up to bring the flow up to optimum.

Under heavy load, the refrigerant is more dense, thus the mass flow/capacity tends to rise (overload). The compressor then slows down to bring the flow down to optimum.

So... the mass flow/capacity is held constant under varying conditions.

mad fridgie
27-10-2009, 02:32 AM
I have little experience with inverters, so I may be wrong on this. As I understand it:

Under light load, the refrigerant is less dense, thus the mass flow/capacity tends to drop (underload). The compressor then speeds up to bring the flow up to optimum.

Under heavy load, the refrigerant is more dense, thus the mass flow/capacity tends to rise (overload). The compressor then slows down to bring the flow down to optimum.

So... the mass flow/capacity is held constant under varying conditions.
Hi inverters are normally driven by the differece between set point and return air temp, the bigger the difference the higher the speed, early on they just a proportiainal (P) band, now they use a bit of "I" and pretty sure they do not as "D", other factors come in like motor current, discharge temps, coli temps (they are more like load limitors, more than a control )method

Gary
27-10-2009, 03:10 AM
I stand corrected then.

cadillackid
27-10-2009, 03:18 AM
they also often utilize electronic expansion valves too which alloows them to maintain optimum pressure across the coils... some use 2 EEV's to keep a precise pressure across the evaporator... the units im using have 3 sensors on the coil... inlet, middle, and outlet..

and of course as im not afraid to play I did just that by pulling those sensors out of the coil.. and boy did that confuse the controller...

you could watch the gauges change pressures even though the "real" temperatures didnt change only the sensors...

my heatpumps like to maintain 115 - 118 degrees center coil temp on heat.. if the room temp is less than 4 degrees warmer than setpoint... between 4 and 7 degrees above the system reduces capacity every 5 minutes until it reaches minimum.... run the room temp up to +7 over setpoint and the unit will cycle out...

about 45 coil midpoint on cool until I reach setpoint minus 1.. then it will reduce till minimum and then shut off if room temp goes to setpoint minus 2...

what this does for me is not only do I respond to the units with the amount of air to push over the coils, the units respond to me as well... if I drop the fan speed way way down it will reduce compressor to maintain the above coil temps.. if I want a slow run up i just tell my units their room temp is warmer or cooler than what it really is... this way i can keep the units running at less than full run-up..
-Christopher