I emailed Pahlen and waiting to hear from them regarding their recomendations. In doing some research regarding hx's I came across lots of information on building them. I am researching possibly building one to test the potential in using the wshp to heat the pool. I came across some people that are using PEX to construst a solar hx and thought that may work for me. I am thinking of using a 55 gal poly drum and install inlet and outlet fittings for the pool side, then construct the coil for the heat pump out of PEX and pvc for a structure to hold it. I am not sure how many feet of tubing I could fit in there but it seems like I should be able to fit several hundred feet in there neatly spaced. Any thoughts on this idea?

Check out a product called Sanicube from Rotex.de
It is an unpressurised solar heated DHW tank and the DHW loop is PEX. It will give you some idea of the amount of heat that can be transferred into water. You should be able to figure out how much tubing is in the tank. Generally I like the idea but the most difficult part is sizing a refrigerant to water HX. Remember that the working pressure of the HP will be up to 450psi.

Posted By MikeSolar on 05 Jun 2012 05:58 PM
... Remember that the working pressure of the HP will be up to 450psi.

Water or Refrigerant ?

Posted By geodean on 05 Jun 2012 07:30 PM

Posted By MikeSolar on 05 Jun 2012 05:58 PM
... Remember that the working pressure of the HP will be up to 450psi.

Water or Refrigerant ?

Refrigerant, but water is only on one side of the HX. I assume the HP is w/a so the big issue is how to replace a air coil with a liquid HX. I tried that a while back with a 2 stage york unit and eventually had to change the control as it didn't like anything custom being done with it.

Better to build your own (if capable) or buy a w/w unit.

Mike I think you are a little confused.

The Air portion of the W/A will remain in tact to gather heat from the home and dump it into water to heat the pool. There will be no need to tamper with the refrigerant circuit.

Yes only on the water side. I found more information on hx's using thin walled nylon tubing because it has better heat transfer than the thicker pex tubing. In a water to water hx it performed as well as copper tubing. I think it would work ok since the water temerature would be under 100 degrees. My thoughts would be to use multiple 1/2 tubing coils neatly seperated to give the most surface area and flow.Then fit as much as I can in a 55 gallon poly drum with a removeable head.

Or throw some thin wall tubing in the bottom of the pool.

Posted By jonr on 06 Jun 2012 04:48 PM
Or throw some thin wall tubing in the bottom of the pool.

Drowning hazard.

Ya think?

Not to mention ugly and likely to interfere with cleaning operations.

Posted By geodude on 06 Jun 2012 07:04 AM
Mike I think you are a little confused.

The Air portion of the W/A will remain in tact to gather heat from the home and dump it into water to heat the pool. There will be no need to tamper with the refrigerant circuit.

DUH, of course

Posted By jonr on 06 Jun 2012 04:48 PM
Or throw some thin wall tubing in the bottom of the pool.

You could put the tubing down and gunnite it. Another skin, so to speak.

Great thread. We have a 15k indoor pool and right now, spring and fall, we heat the pool and cool the house and it works out well.

First we had to add a second heat exchanger (now we have two B-130's) in series with the first to try to keep the temps lower in the geo unit. What we found was the geo unit was running about 20F warmer than the pool. Which was ok in the pool heating, 88F to 108F on the geo. The problem was heating the hot tub up we had 100F on the pool side and 120F on the geo side. With two heat exchanger in series we are now running about 9-10F difference. Our pool pump is a 2hp two speed we run it in low speed 98% of the time, only cleaning do we switch it. When in high we do have a heat pump bypass valve to allow for the higher flows.

The next problem was control. Basically what I did was take a line from the furnace that when cooling is called for it closes the line to the geo heat call, so the house thermostat basically turns on the geo when house cooling is needed. With the pool being large it takes a LOT to swing it one degree either way. The geo is set up to either dump cold to the house or the field, manually switching between them. So sometimes, like now heating up the hot tub might cool the house off to much so I just flip it back to the field for a bit.

In summer I need more cooling that the pool needs heating, we also have a 2 ton air source heat pump, so I let the pool warm up and then switch over to the air source, I can run them both at once giving me 6 tons of cooling, nice for parties or really hot days, I just have to make sure I have bumped up the air flow to match.

For the first two years we didn't have the air source so I ran lines out to an 1000 gallon kiddie pool and let it heat it up like crazy. I found if it got to warm I would just leave the top off and a small fountain really dumped heat at night. I also could circulate the pool water to the radiant floor in the garage and dump heat that way, but having the garage 90+ got to be a bit crazy

And we have a de-superheater as well, it all works well together.

I would like to hear more about your set up and is there any way to get some pictures? What type of heat exchangers are you using for the pool heating? Do you have them inline with a buried ground loop? If you operated your heat pump in the summer for a normal cooling load would it overheat your pool?

Posted By gregs on 07 Jun 2012 08:30 PM
I would like to hear more about your set up and is there any way to get some pictures? What type of heat exchangers are you using for the pool heating? Do you have them inline with a buried ground loop? If you operated your heat pump in the summer for a normal cooling load would it overheat your pool?

The B-130 is the same as the Pahlen products except made by Secespol in Poland.

We have a 4-ton geo-comfort water to water, the unit is reversible. One side is plumbed to the pool the other side is switchable, via manual valves from a 4 ton coil after the furnace or the horizontal field. On the pool side it is the geo to the dual AIC B-130M heat exchangers. They are inline after the filter, with a bypass on the 2" lines

Yes we would overheat our pool if that was our only heat dump in summer, but remember our pool is inside and the shell of the pool was spray foamed before the shotcrete went in so it doesn't loose nearly as much as an outside pool would or could. Heating up the hot tub daily and maintaining the pool at 86F the geo unit runs about 7 hours a day, about 2.5 of that is the hot tub and 4.5 is pool maintaining. That also includes about 90% of our domestic hot water for our family of six.

Here are some pictures.
http://www.uwgb.edu/nevermab/pic/exchanger.jpg
http://www.uwgb.edu/nevermab/pic/geo1.jpg
http://www.uwgb.edu/nevermab/pic/geo2.jpg
http://www.uwgb.edu/nevermab/pic/geo3.jpg

When they did the load calcs on the pool they estimated the 4 ton would run 16-18 hours a day, I really didn't think the pool would loose that much, but I suppose if it were an un-insulated outside pool I suppose it could. We are on time of use or peak electric rates and don't need to run on peak at all for heating.

Thanks for the info and pictures. I am excited to see an actual set up in use and working. I am going to look into the hx you used. If you had to do it again would you have used 1 larger hx? Do you have a salt water pool? I see you have two pool pumps, is one for the pool and one for the spa?

My background is electrical engineering, so I am dangerous with HVAC things

I am not sure if just going larger with the hx or two inline is better. Obviously if the unit could handle a higher flow rate it would be simpler to plumb in a pool system. When working on the design initially HVAC did suggest a separate supply and return line from the pool and he would just use the same circulation pumps on the rest of the system, but after he talked to the pool guys and they discussed using the 2hp pool pump in low most of the time they decided to just plumb in line.

We don't have a salt water, chlorine right now, but when looking at the hx we specked one that could handle salt water just in case we switch down the road, it was also a more robust hx all around anyway. Yes the pump near the geo unit is the spa jets, we also have a 4 hp swim jet with 4 inch lines, moving 300+ gallons a minute

I checked on the AIC website and found some good information. They have a chart for when the B series is used for solar pool heating and recomend a larger B-300 for a 15k pool. Solar use may be similiar to geo in regards to the dT verses using a boiler to heat the pool. I am curious to see how many months of the year I could use the pool as my geo loop. Currently my open well loop just runs thru the hx of the heat pump, but if I go with the hx on the pool side I will need to change over to a closed loop with a circulating pump. So I should be able to add the well water with another set of valves to the new hx for when the pool temp gets to high and be able to switch back and forth as needed and not change the new closed circulating loop.

Well the B300 sounds like a good fit, since I have dual 130's I can confirm this.

I think you will be able to use the pool all summer long, if the pool get really warm you can use a fountain at night or leave it uncovered all the time. Or like you said for a couple of days you could just manually switch back to the well for cooling.

When I was just using our pool I had it up to about 94F and dumped about 3k gallons to get the TDS down and filling it with 55F city water cooled it back down to 85F and gave me some more room. It is kind of neat to sit in a pool at 94F at night, like a huge hot tub. Not so good for playing and swimming in on a hot sunny day though

Currently with the open pool we get a few degrees of solar gain during the day but will loose that with a screened enclosure. I also think with a fountain it would drop it back down at night. I am going to connect a timer I have on my geo unit to see how many hours a day its operating now to get an idea of how long the pool pump would operate. I have a salt water pool and the chlorine generator needs to run a minimum amount of time to generate enough chlorine for the pool. So I need to look into some type of control/timer that could track the run time of the heat pump and if the pool needed additional run time for the day it would operate it. I dont think it would be a problem during the summer but as the temps cool off (spring & fall) it may not operate the pool system long enough.