Home made swimming pool heat pump

[Acuario]

Have you fitted a TEV yet or are you still trying to make it work with the capillary?

Ok, just watched a video on TXV's and their construction. Looks like it'll be an interesting addition. So, as usual some questions;

1. What rating of TXV do I need
2. Do I need one that has the ability to be externally equalized
3. At what point on the suction line does the bulb need to be placed.
4. How do I attach the bulb, a jubilee clip/tie wraps/tape?

Thanks to all!

Nigel

[monkey spanners]

Ok, just watched a video on TXV's and their construction. Looks like it'll be an interesting addition. So, as usual some questions;

1. What rating of TXV do I need
2. Do I need one that has the ability to be externally equalized
3. At what point on the suction line does the bulb need to be placed.
4. How do I attach the bulb, a jubilee clip/tie wraps/tape?

Thanks to all!

Nigel

1. I'd base the TXV capacity on the cooling duty of the original air con system.
2. Externally equalised would be best.
3. Just after the outlet of the evaporator. The equalising line is piped to just after the bulb.
4. The valve should come complete with a clamp, but a jubilee clip will get you going. The bulb needs to be insulated too.

Most TXV's have an instruction sheet in the box or printed on the box itself.

Jon

[nevgee]

Copper in chlorinated water. I've put a spare bit of tube in the filter basket on my pool pump which has to be one of the most volatile places for a tube to be as it has no chance of forming an oxide layer to protect itself from corrosion. So far no change, no degredation, it hasn't even lost its dullness which would be a sure sign of corrosion. I'm going to keep it in there just in case!

The clean copper in your system could also be due to the water scouring the metal and slowly erroding it. If the Ph is low, say less than 0.7 there will be a tendancy for the water to leech metal components. Hence shiny copper.

Oxide layers that form on copper in pool atmospheres are usually "Verdi Gris" which does not provide a protective layer. Over time pin hole penetration will occure, and with the refrig pipework, oil will slowly weep through causing the verdis gris to become pasty to touch.

On another note, There is now a following of operators using Copper ionisation in the pool water instead of chlorine. I believe it's a cheaper method. I have no invormation but yuo can search and find many sites that sell this product.

[Acuario]

1. I'd base the TXV capacity on the cooling duty of the original air con system.

I've no idea what that was, there is no label or anything. Only the model number and initial charge. The compressor is 3Kw and a COP of 3 so what would I expect, 9Kw cooling? From the video they talked about 'tonnes', how does this relate? What measurement do TXV's come in? Kw/Tonnes/something else?

[nevgee]

Some years back, a friend asked me to have alook at his fathers pool heater.

A basic set up with a condensing unit, maybe 1hp, situated within his large green house and a stainless steel cylinder with copper discharge pipework coil running through it. It looked like a home made jobby.

When I connected my gauges on the suction rotolock, water came out

When It was stripped in our workshop, the discharge copper coil was disintegrating,

I managed to replace it, dry out the existing condenser, rebuild it and re-install it back into his greenhouse. It's still going strong

I used 316 S/S tubing though, not copper in the re-build.

I haven't worked on any S & T HX's for pools since, only brazed plate HX's

I have come across many situations simillar to that you mention. We find if we test the water the PH tends to be down below 0.7. At this level the water leeches all metal components. In some cases I've had to return and redo the whole wash out within months of the first repair. One guy was an industrial chemist and thought checking his water 6 monthly would be adequate? every week is essential at the min.

I find worse case is when there are lots of children using the pool for other than swimming. Air born Chloramines rot all the metal work, stainless as well.

[monkey spanners]

I've no idea what that was, there is no label or anything. Only the model number and initial charge. The compressor is 3Kw and a COP of 3 so what would I expect, 9Kw cooling? From the video they talked about 'tonnes', how does this relate? What measurement do TXV's come in? Kw/Tonnes/something else?

A ton is 12000 btu is 3.5Kw.

Whats the model no. and make of your unit?

What make of expansion valve did they have at the wholesalers?

[nevgee]

Sounds like it to me - according to nobility table stainless steel is quite anodic and far away from copper which is cathodic with the result being that the copper will corrode.

There is always that possibility but the majority of corrosion in swim pool apps is not due to electrolytic wasting but chemical reaction. That's why it is essential the chemical balance of the water is kept spot on.

[Acuario]

Whats the model no. and make of your unit?

What make of expansion valve did they have at the wholesalers?

Fujitsu AOG25AWNL. Tecumseh AW5532A compressor.

I can't remember the make of the valves, they only had one make so little choice!

[Acuario]

Ok, went to the wholesalers to ask what they had. The units they sell are Danfoss TX2 devices. He asked which one and I had no idea! So, over to you guys!

[frank]

Your unit is rated at 7.2Kw nominal cooling so your TEX2-(N) needs to be externally equalised with a No.4 orifice (8Kw nominal)

The valve body is the DAN112. The orifice is a DAN208.
The valve will have 3/8" and 1/2" flare connections. The equalising port will have a 1/4" flare connection.
Do you have a flaring tool?

Don't buy the TX2 as this is internally equalised

[Acuario]

Yes, have a flaring tool so no problem. Will go and see if they have this one in stock in the morning and get it installed if they do.

Work interrupted pleasure today so I'll be building the second heat exchanger tomorrow. Have the unit turned off at the moment as I don't want to damage the compressor with excessive heat.

Beautiful sunny weather here at the moment so the solar panels are working hard.

[Acuario]

Your unit is rated at 7.2Kw nominal cooling so your TEX2-(N) needs to be externally equalised with a No.4 orifice (8Kw nominal)

The valve body is the DAN112. The orifice is a DAN208.
The valve will have 3/8" and 1/2" flare connections. The equalising port will have a 1/4" flare connection.
Do you have a flaring tool?

Don't buy the TX2 as this is internally equalised

What part numbers? There are several, I can't find any that has a reference of DAN112 or DAN208, the orifice I guess is part 68-2007.
http://www.kulde.org/CH8/TE2.pdf

Thanks!

[nevgee]

Just bought the bits to make the second condenser so will hopefully make it tomorrow. Still using a capillary but my suppliers have TXV's so will get one and try to work out how to install it. I guess it replaces the capillary, the one he showed me had 2 ports, what looked to be a point to adjust it and what looked like a bulb on the end of a thin coil. Where does this go?
Nigel

Based on your compressor model. The compressor duty at
4.5 barg suction
18 barg disch
has a duty 7.8kW. R22

Expansion valve required
Danfoss TEX2N (without MOP) has duty of 8.9 kW with press drop of 10 b evap at 5C. when using orifice No 03.
As you're able to braze then the better option of valve would be one you can braze into the sytem.

TEXN part number 068Z328400 (solder)
plus
Orifice 03 Part number 068 209300
plus 3/8 solder adaptor 068 206066


There is a 25% leaway with these valves on their duty and of course you may need to adjust the superheat once up and running.

[nevgee]

Your unit is rated at 7.2Kw nominal cooling so your TEX2-(N) needs to be externally equalised with a No.4 orifice (8Kw nominal)

The valve body is the DAN112. The orifice is a DAN208.
The valve will have 3/8" and 1/2" flare connections. The equalising port will have a 1/4" flare connection.
Do you have a flaring tool?

Don't buy the TX2 as this is internally equalised

Sorry to butt in here Frank.
I think you may be quoting nominal duty for the orifice wich is only based on a 2 bar dp across the valve. this application is most likely to have 10 bar dp across the valve. in that case an orifice No. 03 would be most suited as it's duty is 8.9 kW Whereas the no.04 orifice will have a duty of 13.3 kW ... too high I think.

[nevgee]

links where you can get details of the Danfoss valves.

http://www.ra.danfoss.com/TechnicalI...AA0A402_T2.pdf

http://www.ra.danfoss.com/TechnicalI...CPDAA0A402.pdf

[nevgee]

What part numbers? There are several, I can't find any that has a reference of DAN112 or DAN208, the orifice I guess is part 68-2007.

Thanks!

See above post

[nevgee]

This link may be helpfull ... Danfoss "Fitters notes" gives instructions on Expansion valves and setting them up.

http://ra.danfoss.com/TechnicalInfo/...chapter_01.pdf

[nevgee]

Parallel, pipe it is parallel. I would think the pressure drop is important. Des, Gary?

I think you're quite right here. Does Acuario have the necessary information to pipe up the second condenser, taking into consideration the gas flows to ensure even balancing and equal flow through both condensers?
Perhaps someone has got some typical pipework arrangements that he could follow. Otherwise I fear he may hook up the 2nd condenser and find his gas flows are wrong.

[nevgee]

Attached Danfoss pages with TEX selection data

[frank]

I was using the RPW Catalogue

[nevgee]

I was using the RPW Catalogue

Maybe you need to refresh your glass and try different brew?

[Acuario]

Well I opted for Heat Exchanger MKII instead of a second MKI in parallel, I could always parallel them up if necessary.

MKII has more coils; 3 to be precise, coil 1 wound on a 32mm former, coil 2 wound on a 50mm former and coil 3 wound on a 75mm former. All then fitted one inside the other and linked at either end. The pipe in each coil is 1/4" diameter. Coil 1 is about 6m long, coil 2 about 9m long and coil 3 about 15m long (now you're going to tell me they should all be the same!).

They are all contained in a 110mm diameter pipe 68cm long.

As I write I'm waiting for the glue to finish drying. I'll post pictures later.

My supplier isn't open saturday afternoons so I'll go and order/purchase the TXV on monday.

[nevgee]

Well I opted for Heat Exchanger MKII instead of a second MKI in parallel, I could always parallel them up if necessary.

MKII has more coils; 3 to be precise, coil 1 wound on a 32mm former, coil 2 wound on a 50mm former and coil 3 wound on a 75mm former. All then fitted one inside the other and linked at either end. The pipe in each coil is 1/4" diameter. Coil 1 is about 6m long, coil 2 about 9m long and coil 3 about 15m long (now you're going to tell me they should all be the same!).

Ideally, yes. You really need to try to ensure the gas flows are equal through the sections of the condenser.

Had you not considered using a tank instead of a pipe to contain the coils?

[nevgee]

I have come across many situations simillar to that you mention. We find if we test the water the PH tends to be down below 0.7. At this level the water leeches all metal components. In some cases I've had to return and redo the whole wash out within months of the first repair. .

Sorry for my error ..... should have read 7.0 not 0.7.

The ph of a swimpool water should ideally be 7.4

[MikeHolm]

If you are able to ensure roughly even flow over each of the coils, they should be of roughly equal lengths of tubing although, I believe, the coil with a larger helical diameter will have a slightly smaller pressure drop.

[Acuario]

Here we go again, a disaster, bad weather and work got in the way but at last I'm off again..
The disaster - I managed to leave a small unbrazed hole in HX MKII and flooded my evaporator etc . I also managed to dump my charge of R22 into the pool at the same time . So, a change of refrigerant and a bit of a clean up was in order..
Blew everything out with Nitrogen and it is up and seems to be running again. As there was no refrigerant left, and I was concerned about any moisture in the compressor (I'm sure there was) I added a filter dryer and at the same time cut out the capillary and installed a TXV.

The TXV is a Danfoss TX2, 068Z3206 and I fitted orifice No. 03, but without filter as that was all he had.

So, it's running again with a new refrigerant, RS44 (R424A), slightly different PT characteristics but it's a drop in replacement.

Measurements are (fan at full speed):
Compressor exit temperature: 53.5'C
Pressure 112psig
Condensor entry 53.1'C
Condensor exit 16'C
TXV entry 14'C
TXV exit (evaporator entry) -1.8'C
Evaporator exit 5.9'C
Suction pressure 37psig

Tuning advice welcome!

Nigel

[Gary]

Here we go again, a disaster, bad weather and work got in the way but at last I'm off again..
The disaster - I managed to leave a small unbrazed hole in HX MKII and flooded my evaporator etc . I also managed to dump my charge of R22 into the pool at the same time . So, a change of refrigerant and a bit of a clean up was in order..
Blew everything out with Nitrogen and it is up and seems to be running again. As there was no refrigerant left, and I was concerned about any moisture in the compressor (I'm sure there was) I added a filter dryer and at the same time cut out the capillary and installed a TXV.

The TXV is a Danfoss TX2, 068Z3206 and I fitted orifice No. 03, but without filter as that was all he had.

So, it's running again with a new refrigerant, RS44 (R424A), slightly different PT characteristics but it's a drop in replacement.

Measurements are (fan at full speed):
Compressor exit temperature: 53.5'C
Pressure 112psig
Condensor entry 53.1'C
Condensor exit 16'C
TXV entry 14'C
TXV exit (evaporator entry) -1.8'C
Evaporator exit 5.9'C
Suction pressure 37psig

Tuning advice welcome!

Nigel

112 psig for R22 (from P/T chart) is about 19C-16C (exit temp) =3K subcooling. Add refrigerant slowly until the subcooling is about 8.5K.

[Acuario]

I had a small leak so had to remove the gas, fix it and re-gas. Obviously readings changed...
I also spotted I put a wrong value - too many scribbles on my bit of paper!
A new bit of paper so no confusion!
Readings are:

Ambient: 15'C
Water: 20'C
Exit pressure: 167psig
Exit temp: 64'C
Condensor entry: 61'C
Condensor exit: 26'C
Evap exit: 11'C
Suction pressure: 38psig

So, following the above I have subcooling:
32.2 - 11 = 21.2K

Is this too high? Should I try to reduce it?

Nigel

[Gary]

I had a small leak so had to remove the gas, fix it and re-gas. Obviously readings changed...
I also spotted I put a wrong value - too many scribbles on my bit of paper!
A new bit of paper so no confusion!
Readings are:

Ambient: 15'C
Water: 20'C
Exit pressure: 167psig
Exit temp: 64'C
Condensor entry: 61'C
Condensor exit: 26'C
Evap exit: 11'C
Suction pressure: 38psig

So, following the above I have subcooling:
32.2 - 11 = 21.2K

Is this too high? Should I try to reduce it?

Nigel

That's 32C-26C=6K

[nevgee]

I had a small leak so had to remove the gas, fix it and re-gas. Obviously readings changed...
I also spotted I put a wrong value - too many scribbles on my bit of paper!
A new bit of paper so no confusion!
Readings are:

Ambient: 15'C
Water: 20'C
Exit pressure: 167psig
Exit temp: 64'C
Condensor entry: 61'C
Condensor exit: 26'C
Evap exit: 11'C
Suction pressure: 38psig

So, following the above I have subcooling:
32.2 - 11 = 21.2K

Is this too high? Should I try to reduce it?

Nigel

38psig = 2.6 barg = -9C sst Too low
super heat -9 -11 = 20C Far too high

Add gas as Gary suggests and open TX valve to reduce Sh. approx one full turn counter clockwise will give 4 C .. so 2 to 3 full turns might do the trick. Check instructions on box. Do it at 1 turn at a time and allow 10 - 15 mins for the system to settle down each time.