Hotspot FPH AC heat reclamation pool heater - a review!

[CaptainCannonball]

For some reason you don't seem to see many heat pumps here - pretty much all you see is NG. The capital cost for a heat pump appears to be about 2X what heat pumps are. When I go to a Canadian online pool retailer for my 18x36 pool they recommend a 250,000 BTU heater which are about C$2000. For heat pumps they recommend 125,000 which are about C$3800. Any idea what the average operating cost difference would be between the two? Food for thought when I have to replace my ten year old natural gas heater. Any downside to the heat pump, like taking longer to heat up?

I see in your signature that you have evacuated tube solar. Is that plumbed into your pool? I was under the impression those were primarily used for home water heating. I.e. Designed for lower flow, very high temperatures and use an exchanger.

Solar isnt a solution for everyone, but if it is a possibility you might consider a couple hundred square feet of unglazed pool solar panels. They will probably net you far more btus for the money.

 

[Flying Tivo]

First realIf you're even slicker you could run it all through your easy touch.

If you have automation like the ET, it can handle the exchanger without the Brains of the Hotspot. I called CS at Hotspot and explained them what the ET does with solar and its basically a relay that opens a selenoid, which can do the same for the AC unit. This means that the refrigerant will only flow to the exchanger when ET calls for heat and operates the Pump to circulate water. So you can save some $$ if you have ET.

Felipe

 

[Joshii]

I detest waste, and when I saw an ac compressor spewing hot air next to my pool, I wanted so badly to be efficient and reclaim that heat. I hesitate to post this because I don't want to hurt anyone's feelings, but logically the btu's just don't add up.
...

It is good to have an honest conversation around new technology. That's why I started this a few years ago because there is a lot of conflicting and dubious information out there.

If you take a look at this thread, the system works for us who have it. It does exactly what we hoped it would -- keep the temps up during the nice warm swimming months.

A heat pump would have done the same in about an hour and its power consumption would easily be offset by reducing pump time.

You seem to be under the impression this is competing with dedicated heat pumps. It is not. This is a passive unit that heats the pool for free. A heat pump cannot compete with that cost of use, and the FPH cannot compete with how a heat pump can force a pool to a temperature.

This is competing with other passive systems, such as solar. And if we want to have an honest conversation about the drawbacks of that system, you have to install a huge array of solar panels on your roof, which is risky from an installation perspective, and which some may say detracts from the overall look of the place. It only works when it is sunny out. And you run the risk of a leak dumping chlorinated water all over your house. The FPH works whenever you want to run the AC, day or night, rain or shine. And that's pretty much all the time in the summer. It is also virtually invisible (see my install pics), has a negligible effect on pump use / pressure head, and is quieter than actually running the AC with its huge noisy fan. A big win for me and the others who have it.

The drawbacks as I see it are the upfront costs (more than solar, on par with active heating systems), difficultly of finding the HVAC contractor to install, and I hope when I run into problems they can be fixed (always a risk with new technology)

 

[The dog]

I'd use it as a supplemental device, in conjunction with my gas heater, to capture unused heat from the hvac. Besides it seems to make the hvac system run more efficiently. In fact, most ac units are designed for 105 degrees. So when the outside temp gets over 105 the ac doesn't work as well. By using this device you don't need to worry about the outside air temp.


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[pooldv]

I can definitely see the hotspot helping with supplemental heat during summer in northern climates where the pool needs heat in June, July, August. For southern climates the pools don't need heat during summer they need heat during spring and fall when the AC in the house isn't running yet. We are heating the pool from March to May and October and November. We are cooling the pool in July and August by running solar at night.

 

[CaptainCannonball]

You seem to be under the impression this is competing with dedicated heat pumps. It is not. This is a passive unit that heats the pool for free. A heat pump cannot compete with that cost of use, and the FPH cannot compete with how a heat pump can force a pool to a temperature.

This is competing with other passive systems, such as solar.

I disagree, this system is competing with all other systems that provide btus to pools. The only real passive system is a so called solar blanket. All others cost money to run like solar, heat pump, gas...

The problem is, you must supply 60gpm to the exchanger as you say, day or night, rain or shine... doesn't sound free to me. In fact, it reinforces my point that by cutting out 16 hours of pump runtime a day would easily offset running a heat pump that would provide more btus for the money spent.

 

[CaptainCannonball]

I guess I also feel like I should mention that if a roof mounted solar system fails and pours water on my roof that is designed to shed water I wouldn't be too concerned. Now if I owned a heat exchanger, that transfers heat from air conditioning coolant and compressor oil to my pool, that failed...

 

[Joshii]

There can be a significant hidden expense in running your pump for solar heating. Not so for this system. Vastly different pump use. This system requires nothing more from your pump and its primary operating times dovetail with pump use already.

 

[JoyfulNoise]

The most interesting heating option I've seen so far (and it costs significant $$$) is a local company in Tucson that installs solar PV near the pool pad to run a heat pump. This way, you get to capture and use solar energy for electricity generation and that electrical power drives an efficient heat pump (excess power can be used to offset utility power used by the pump) . You only heat a pool during the day (for the most part) so it works as as efficient as pumping water up to a roof to capture heat...and if the heat pump can be used in COOLING mode, the solar power can be used to cool hot pool water.

White Paper here - http://esmeps.com/images/Engineered_Solar_Pool_Heating_Options_Summary_4-15-2015.pdf

 

[CaptainCannonball]

There is nothing hidden about running my pump at 900 watts for 8 hours. 7.2kwh.
if I didn't have solar, I would run my pump at half the speed. Meaning my 400-500k btus a day cost me less than 4kwh.

Doesn't the pump have to run for the Free Pool Heat system to operate?

 

[The dog]

Captain. I don't think it works that way. The pictures show a refrigerant line going in and out of the blue barrel. It's a closed system. Refrigerant, oil, etc doesn't come out of the ac lines.


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[CaptainCannonball]

I was just pointing out a failure mode, when the heat exchanger fails, what happens?

 

[Joshii]

That's right. Its hidden in the sense that people may not take it into consideration when thinking about the costs of running the system.

In your example, the cost of running solar (at $0.2/kwh) for a month is about 20 bucks. Since you do not need to run at full speed for the FPH, that additional cost would be less, possibly 0. To be honest, both cases are cheap, cheap money.

And that's the point. People installing solar or the FPH do so because they don't want to spend hundreds a month heating their pool. But they do work, they work well for their use case, and one must understand the use case is different than the use case of an active heater.

 

[The dog]

Capt. what part are you taking about to fail ? Obviously if the compressor fails your whole system goes down. If the pump fails then your ac system runs a little hotter? If the blue barrel springs a leak, you loose pool water thats the biggest issue I see.

There is always a weak link somewhere.

The only thing I can think of doing would be to install a separate pump for the heat exchanger. Or maybe hook it into a booster pump. But you would need to mess with your plumbing to do that. You might even need to install a flow switch so if the flow stops the pumps automatically shut down. All That can be accomplished with existing hvac and pool parts. Then hte cost comes back in to play. That's really why Cogen hasn't really started to catch on (other than in a manufacturing facility where you can get a benefit if there is a lot of waste heat available).

I get what the other guy is complaint about when the main pump needs to cycle based on the ac/heat exchanger needs.


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[CaptainCannonball]

That's right. Its hidden in the sense that people may not take it into consideration when thinking about the costs of running the system.

In your example, the cost of running solar (at $0.2/kwh) for a month is about 20 bucks. Since you do not need to run at full speed for the FPH, that additional cost would be less, possibly 0. To be honest, both cases are cheap, cheap money.

And that's the point. People installing solar or the FPH do so because they don't want to spend hundreds a month heating their pool. But they do work, they work well for their use case, and one must understand the use case is different than the use case of an active heater.

So I need to provide my panels 55gpm roughly the same requirement as the AC heat exchanger. How does that cost me more? Especially since I only run it 8 hours a day? Now Heliocol propaganda says I get 76,121btu per panel per day x 11 or 830k btus per day... My real world measurements indicate I get probably a little more than half that.

I've discussed theoretical maximums for AC heat exchangers that don't come anywhere near worst case scenarios like my north facing roof mount solar.

Honestly, I don't like a this vs. that thread, so I will not mention solar again. I promise!

I would like to ask you or anyone else running this type of system a few short questions. With the the AC exchanger, how many hours a day do you run your pump? Do you maintain the recommended 60gpm? How many btus do you believe you are harvesting from your AC?

 

[Joshii]

The min/max gpm for the FPH heat exchanger is 33/50. Not sure where the 60 gpm is coming from.

I've run it accidentally with very little flow when I had a filter issue. The water coming out of the returns was very warm but I had no issues with either pool, pump, or AC during that time or after.

I run the AC normally. That typically means from 2pm onwards. I try to match pump running with AC use. I run the pump for about 8-12 hours a day. I'm going to be getting a VS pump soon, and I will run that at low speed 24-7. I expect that will be enough flow to also run through the FPH without needing to bump up pump RPM. If not the FPH can send out a 24VAC line to make the pump go faster.

I estimate I get 30k btus/hr when operating the AC. It takes about 8 hours of operation to get my pool up 1 degree F. It is not a fast heater, but it is really nice I have to say. I no longer feel guilty about running my AC. I can keep my house as comfortable as I want, and my pool reaps all the benefit.

 

[catiare]

I'm considering installing the FPH by the end of September. I live in Miami where we run the AC 24-7 except a handful days a year - however water can get cold (by our standards) from November to March yet average temperature is in the high 70's. Also the pool gets shade most of the day at that time of the year, making it even cooler.

I'm assuming I can operate the exchanger with the pump on low speed. One of the posters said that the AC compressor on proper operation only runs 30-50% of the time. So if I compare that to running the pump at low speed 24x7 (I cannot turn it on-off like the compressor) still the savings are more that half. Using current as the metric, my 2HP pump in low speed runs on 3A and my 4-Ton compressor is 20A. So running the compressor for 8 hours on average we are looking at 160A-Hr per day vs running the pump in low speed for 24 Hours for 72A-hr. That is less than half the amount of current ($$).

Let me know if my rationale is correct (at least in paper). If that is the case, its worth not to use Compressor at all and just water-cool the AC and the by-product is a warmer pool!

Regarding wear and tear issue, its either the Compressor or the Pump, and the latter is a lot cheaper to replace.

 

[Joshii]

I'm considering installing the FPH by the end of September. I live in Miami where we run the AC 24-7 except a handful days a year - however water can get cold (by our standards) from November to March yet average temperature is in the high 70's. Also the pool gets shade most of the day at that time of the year, making it even cooler.

I'm assuming I can operate the exchanger with the pump on low speed. One of the posters said that the AC compressor on proper operation only runs 30-50% of the time. So if I compare that to running the pump at low speed 24x7 (I cannot turn it on-off like the compressor) still the savings are more that half. Using current as the metric, my 2HP pump in low speed runs on 3A and my 4-Ton compressor is 20A. So running the compressor for 8 hours on average we are looking at 160A-Hr per day vs running the pump in low speed for 24 Hours for 72A-hr. That is less than half the amount of current ($$).

Let me know if my rationale is correct (at least in paper). If that is the case, its worth not to use Compressor at all and just water-cool the AC and the by-product is a warmer pool!

Regarding wear and tear issue, its either the Compressor or the Pump, and the latter is a lot cheaper to replace.

Hi Catiare,

It doesn't work like that. The compressor still needs to run. The outside AC fan doesn't run. That saves a few hundred watts. The compressor also runs more efficiently, not needing to do as much work. That saves some $$ too. But it still needs to run. But you would have to run your AC and pump anyways, so connecting them together gets you pool heat for free.

 

[catiare]

Oh I see. Thanks for the clarification!

 

[OneLoveAmaru]

You're right. This is not for everyone. I was lucky. Small pool, Ac on same side as pump. I did have to get a new VS pump, as my hayward VS, not compatible. Just turned on new system tonight...ran system for 45 mins. Water rose from 77 degrees to 81 degrees during our test. AC much more efficient. We live north of Tampa FL. I can't share installer with you. He can blog if he is interested in doing another. I hope he will.

I know you can't share the installers info but can you ask them if they are interested in installing another one? I can't seem to find someone here in Tampa that'll do it. If they say yes they are interested, I can send you my contact info for them to contact me.

Thanks!