Hotspot FPH questions

[applegrcoug]

Last summer my AC decided when it got too hot to go on strike due to unsafe working conditions. It has been fired, and now I am interviewing replacements.

Last summer when this all went down, i stumbled upon the Hotspot FPH heat reclaiming devise and was intrigued. I have since read through the big eight page thread here and am intrigued more than ever.

I live in a brick home with little shade on the south side of the house that is serviced by a 40 year old 4ton AC that is dying. One of the local HVAC contractors did a manual J load calculation for my house and my theoretical cooling load is 6.5 tons, but said my duct work is only large enough to handle 4tons. That came as no surprise considering my AC seems like it goes flat out 24/7 from mid-June until the end of August. It actually starts up in May and runs through September, so it puts on a fair number of hours every year.

My pool is an in ground 18x36 gunite pool on the east side of the house, so for a good portion of the day it is actually in full shade cast by the house. I have a big natural gas heater, but to maintain the temperature in the mid-80s, it has to run a lot. I figure last year, I used 100 therms for July and then another 100 in August to keep it warm just for the weekends. Without heat, the equalization temp is somewhere in the mid-70s. Yes, I have a cover...a dark blue automatic one.

i figure, i am a good candidate for one of these gizmos, and the time is right considering I have to rip out all the AC anyway.

So, I have some questions and thoughts:

Is the conventional wisdom that it would void the warranty of a new AC, despite what hotspot says under their FAQ? Have any of you had any problems where it has caused the AC to have a problem?

Hotspot says it will make the AC work more efficiently. Have any of you been able to see this? Is it enough to offset the power needed by the pump running all the time to keep water circulating?

Hotspot also says for every 12,000BTU of cooling capacity, there is actually 15,000BTU of energy out there being used. Has anyone done any sort of math to see how much they think they are harvesting?

Any other tips or things to think about?

Thanks-

 

[JoyfulNoise]

I’ll let HotSpot people answer those specific questions but I do have a slightly tangential one -

Have you considered a geothermal heat pump for your home instead of a conventional air-source system?

If your heat load is 6.5ton and your duct work is limiting you to 4 ton, then your A/C is running all the time. A geothermal heat-pump is more efficient than an air-source heat-pump ( conventional A/C unit) so perhaps the added installation expense of a geothermal system might be offset by the higher efficiency of a ground-source heat extraction ? Just a thought ....

Also, a really smart geothermal company might be able to tie the system into your pool to give you added heat to the pool when you want it.

 

[applegrcoug]

I’ll let HotSpot people answer those specific questions but I do have a slightly tangential one -

Have you considered a geothermal heat pump for your home instead of a conventional air-source system?

If your heat load is 6.5ton and your duct work is limiting you to 4 ton, then your A/C is running all the time. A geothermal heat-pump is more efficient than an air-source heat-pump ( conventional A/C unit) so perhaps the added installation expense of a geothermal system might be offset by the higher efficiency of a ground-source heat extraction ? Just a thought ....

Also, a really smart geothermal company might be able to tie the system into your pool to give you added heat to the pool when you want it.

I don't have the space or access for geothermal.

 

[kefjens]

Do a search here on the FPH, at least a couple of people have them and you might be able to PM them so they can answer your questions. The FPH is essentially a geothermal system using your pool as the heat sink for your liquid to liquid heat exchanger.

If you do end up using it, please post how your install goes and any follow up on your perception of its efficiency.

 

[Joshii]

I'm the one who wrote that original review. I think the FPH would be ideal for your use case. It will indeed make your AC run more efficiently, though I don't have hard numbers on how much since I run my AC more often now that the waste heat is all usable. The biggest challenge will be finding a competent HVAC installer who is willing and able to do the modifications necessary and install the system. Good luck. Let me know if you have any additional questions.

 

[hjunco]

I just ordered a FPH Hotspot system for a new pool and I currently waiting for the contractor to make the connections, install and finish the pool. Will report back regarding the install and the performance of the system and what not.

 

[applegrcoug]

Finally got my FPH and new AC up and running yesterday. Two weeks ago, I used the NG heater to take the temp up to 88F for a party and then promptly shut it off because everyone in my family except me was leaving town. The next ten or so days, we had highs in the 90's and then the last four it has been in the 70's. Despite all the warm days, when left to being natural without NG supplemental heat, water temp slumped to 78F. The next week the forecast is to be in the mid-70's, so it should be interesting to see what happens.

 

[Joshii]

Thanks for the update. Let us know!

 

[applegrcoug]

After a week in operation, my pool made it to 84F. It actually did it in the first few days and then maintained. The past week has been less than ideal.

Temps from the airport a few miles away:

June 10th, pool water at 85, switched off gas heater because family was leaving town. I kept the cover on and let the pump continue to circulate as before. Only difference was no supplemental heat.

June 10 89/49
June 11 88/54
June 12 93/54
June 13 97/59
June 14 89/57
June 15 90/49
June 16 92/63
June 17 92/67
June 18 86/60
June 19 72/51
June 20 72/52
June 21 80/55 Pool water down to 78. FPH operational.
June 22 84/47
June 23 78/48
June 24 78/51 (pool temp was 84 on this day)
June 25 80/51
June 26 76/45
June 27 75/46
June 28 77/41
Pool temp currently at 84

As stated before, even when in the 70s, because my house is brick it gets pretty warm inside, so the AC tends to run a fair amount.

Initial observations which seem to echo others on here.

1. My pool loses heat quickly. I knew this before, but it really loses heat quick even when it is hot outside.
2. The FPH really should not be thought of as a tool to bring your pool up to temperature. I ran the math, and when running, I figured it would take five hours of continuous operation to add 1F with no loss.
3. The FPH does a good job at maintaining temperature. In my situation with a house that gains a lot of heat and an undersized AC it really works pretty well at maintaining pool temps. My first few days I added temp when it was a little warmer outside, but then cooler temps combined with wind and cloud cover took over and at best it maintained.

 

[mknauss]

Did you have your cover closed during the test?

 

[applegrcoug]

Did you have your cover closed during the test?

Indeed.

At the end of week two, with day temps in the 80s, pool water is at 88.

 

[Joshii]

We're having awesome weather in the northeast right now. 90s every day. I came home from a vacation after having AC off for a week: pool at 81. Within 2 days of running AC, pool is at 88.