HVAC to Pool heat exchanger

[250]

I'm curious if anyone has any experience with using a heat exchanger that pulls heat out of the refrigerant of the HVAC and dumps it into the pool? The one I'm looking at specifically is made by hotspot energy and got a feature plug on This Old House, but I'm sure there are variations on a theme out there.

Heat Recovery Pool Heater | Compare To Solar Pool Heater | HotSpot Energy LLC

I've been trying to find someone local to do the HVAC with not much luck. No one returned any of my phone calls, so I started walking into business and asking. The responses have been tepid to cold. One guy tried to talk me out of it saying I wouldn't like it, but I suspect they just didn't want to do it. Maybe someone here can fill in the gaps for me.

Thanks,

 

[mike93lx]

The times of the year when I really want to get heat into the pool don't really line up with when my ac is running. That aside, I doubt it will make much of a difference for most people. My pool heater is 120k btu. The total of all three of my a/c units is 75k btu. Sure, there is some heat, but enough to matter? A solar cover is probably more effective

 

[fitter30]

Water cooled condenser made for pool water would replace the finned air cooled condenser along with its own pump. It would very hard to make a system that could use both the air cooled and water cooled condensers switching back and forth. Compressor oil return and proper valving would be a major hurtle. The other problem would be head pressure control normally a head pressure water regulator valve would be used but haven't seen one for refrigerant 410a. Flow control valve could be used with a pressure sensor. PoolPac makes units for natatoriums that use air and water condensers take work great for both heating and cooling. ( if you have to ask what they cost you can't afford them)

 

[FredWanaker]

actually it would make more sense to add a second coil that picked up the heat from the first to drive a small freon driven electric generator that powered an electric heater element used to heat water.

 

[Aileron]

Its called heat reclaim, but for a residential house and unless your heating a wading pool I doubt your going to see much. for the effort and expense. If you had a grocery store were a rack was running 24/7 it may be a different story.

 

[American Locomotive]

Most HVAC companies barely want to do anything more than condenser fan changeouts. This heat exchanger is not an easy device to install. It requires significant reworking of the condensing unit's piping, the addition of refrigerant switching vaves, and tons of wiring changes. No HVAC company will want to own that.

 

[gregs]

I have a water to air heat pump for my house. Its currently setup as an open loop system using a well. I looked into using a separate heat exchanger and plumbing it into the pool plumbing. After much research with both efficiency, pool water chemistry, and the amount of time during the year that it would actually be feasible in my climate I decided there was no payback. In the winter your making cold water and in the summer hot water, so for me there is maybe 3-4 months that it would be beneficial to the pool temp. Wasn't worth all the trouble.

 

[250]

Thanks for the replies. I'm not one that wants a cold pool, and the shape of the pool won't allow for any sort of easily removable solar cover unfortunately. This seemed like a good idea with AC season often starting in early May.

 

[Jackfre]

I think you will be best with the heat pump pool heaters being sold. A friend works at Raypak and tells me they are doing very well with theirs.

 

[mike93lx]

I think you will be best with the heat pump pool heaters being sold. A friend works at Raypak and tells me they are doing very well with theirs.

I would hope a $3-8k heater would work better...

 

[Denwood]

You are losing a massive amount of energy to evaporation with no cover. It's not just the radiated heat lost at night, but also the heat consumed in the change of state from liquid to gas (evaporation). Conditions depending, you could be losing 50% of your heat via evap.

Consider rooftop solar. That's all we use, and our pool is North of the 49th parallel. We generate approx 600K BTU per day from 320 square feet of collectors. The roof is shaded until about 11 am, and again, we're up North so a system in your climate with decent sun would likely produce even more. With part of your roof effectively water cooled, your AC costs will drop too.

Our 18ft above ground pool has been a bit of science project for me, ha : https://community.smartthings.com/t/smartthings-swimming-pool-solar-heat-automation-diy/131994/16

 

[Denwood]

... and for the record, I think using your pool to capture AC "waste" makes 100% good sense too. These folks use a titanium heat exchange:

Heat Recovery Pool Heater | Compare To Solar Pool Heater | HotSpot Energy LLC

My sister lives south of us (much warmer climate) and has an in ground pool. They don't cover it (ever) so on a 90 degree day their 3 ton AC unit is clacking away to cool their 4000 sq/ft house, and then their 400K BTU gas heater fires up to heat a completely uncovered pool. There is so much wrong with this scenario that I literally cringe at the energy logic behind it. Then I look over at the neighbours and it's the same scenario. Using the large heat sink (your pool, with water's ability to store a lot of heat) to cool your house though makes a lot more sense. These houses are all in the $800K to $1.3 million range, and no one cares much about the waste

 

[mike93lx]

... and for the record, I think using your pool to capture AC "waste" makes 100% good sense too. These folks use a titanium heat exchange:

Heat Recovery Pool Heater | Compare To Solar Pool Heater | HotSpot Energy LLC

That's the one originally linked by the OP and what this whole thread was about

 

[Denwood]

My bad I would 100% install one in a hot climate with a lot of AC use in combination with solar if needed.

You're going to the use the AC energy anyway so why not dump that back in the pool! This thinking is not inline with a lot of HVAC installers deal with, so you will need to shop around a bit. In more temperate climates it may make less sense than in hotter, so you may still need to supplement with solar etc. if your pool is shaded. This is why local installers may not favour adding an AC heat exchanger ... and they won't want to install or support a system they are not familiar with.

 

[mike93lx]

My bad I would 100% install one in a hot climate with a lot of AC use in combination with solar if needed.

You're going to the use the AC energy anyway so why not dump that back in the pool!

Adding heat to a pool, especially in a hot climate, is not always desirable.

My pool heat pump has a chiller function to pull heat out of the pool. In a hot climate, heat for the pool is needed in spring/fall when a/c isn't needed as much

 

[Denwood]

I get that...particularly if your pool is in full sun. We're in a cold climate, pool shaded for 80% of the day..and AC in use for 2-4 weeks in summer....so an AC heat exchanger would make zero sense here.

Solar does work great though

 

[rancherbill]

This is a neat idea. It will be a great supplemental heat source in the pool heating system.

 

[mike93lx]

I get that...particularly if your pool is in full sun. We're in a cold climate, pool shaded for 80% of the day..and AC in use for 2-4 weeks in summer....so an AC heat exchanger would make zero sense here.

Solar does work great though

Solar works awesome. My folks have heated thir huge inground pool in MA for almost 30 years with solar, although diligently keeping it covered helps a ton

 

[justinjoyal]

Pool heat pump is useful to heat a pool, save money, green energy

"Save" money, "green" energy.

We're all trying to make ourselves feel better about heating a damn outdoor pool.

 

[250]

None of the adults in our house are keen on a cold pool, even in the heat of summer. We have pretty thin blood, and skinny butts so that's that. No polar bear swims for us.

Jackfre- a propane unit (that's the fuel of availability here) isn't on the table. We actually sold the 400k btu unit that came with the pool. Cost of propane is too high.

Denwood- that was an interesting read you linked. I appreciate all the nerding that went into it, though I don't think I have the skill to replicate the automation at this point, though I'd like to think I could. I looked up those solar heaters you listed. 2x the cost you paid but still might be worth coming up with some system to experiment on.

We'll fight an up hill battle without a cover. She won't go for any cover that doesn't support the weight of a person when closed. And it looks like I probably can't talk any HVAC people into taking on the job unless they get to do some other work that they're more interested in as well.

Some more head scratching for sure. That's free.

 

[mike93lx]

We'll fight an up hill battle without a cover. She won't go for any cover that doesn't support the weight of a person when closed.

That makes it tough. You are going from a few hundred for a solar cover and reel to thousands for an auto safety cover

 

[Gila Monster]

I'm all for crazy ideas, but my shoot from the hip is this system will never come close to paying for itself in terms of energy savings and be a massive headache to build and service. Just something else to break for pretty menial results.

As an example of just one of the obstacles, I recently had a main water line replaced at my house that somebody put under a concrete driveway with no sleeve. A lot of man hours and expense for a pretty straight forward job. Just running underground recirculation pipe(s) to your pool (and under the patio and into the plaster that holds the water) from your HVAC condenser is a decent expense all on its own (depending on how things are laid out). Where my equipment and pool is at (not close together and under a variety of obstacles), this alone would probably be $3k-$5k job for an outfit to do to just to run the pipes, not including all the other elaborate equipment that also is needed.

Something like a solar cover for the pool or even a darker finish on the plaster (like pebble tec instead of white plaster) would probably do a much better job than this engineering nightmare of heating the pool for "free".

If you're really into being green, bury the pool and get rd of it. Or put PV solar panels on your roof. Way easier.

 

[250]

Ha, gila, tell us how you really feel. I'm not ultra green but I see no reason to waste energy, or heat, if one doesn't have to. I think the concept has merit, hard to say it would be as fruitful as I'd hope. Can't find anyone interested in doing the HVAC side so its probably stalled out.

I'm going to start looking into tying in some solar heaters in. That will mainly be seeing if our pump has the capacity to pump up to where solar heaters could go.

 

[Denwood]

Your existing pump is likely more than enough to pump up 1-2 stories. What voltage/amperage is it? Anything over 7 amps @120V should be good for 25-30 feet head.

If you keep on eye on local buy/sell (FB, Craigs, Kijiji etc) you can often find panels or entire panel packages for a lot less than new.

Square footage will depend on the pool surface area, climate and solar exposure to pool and roof. There are free estimators online.

There are liquid pool covers..sounds crazy but it may be a option.

Automation for me is a fun distraction, but if you are around the home a lot, you can take care of things manually with just a 3 way valve to include or exclude your solar loop. The best buzz for your buck is likely Haywards solar control system that comes with a controller, 3 way valve and two sensors…$500 or so USD.

 

[250]

One of us works from home, so real automation probably isn't necessary.

Do you still have pressure on the downstream side of the panels or are you passively feeding into your pool?

 

[Denwood]

There is a lot of pressure on the downstream side… system head is 17ft



these measurements were taken before adding 4 more collectors. The max BTU measurement now are in the 125K BTU range, but with 8 2’x20’ collectors. Flow is still in the 1500 GPH range.

When you add collectors in a parallel flow setup, you actually reduce resistance, so flow will increase. Some of these collectors are set up so that water goes up on one half and back on the other. That is a very bad setup for efficiency, so I drilled out the internal block and turned them into unidirectional collectors.

 

[250]

I didn't get the pump info in before. Pentair 3hp variable speed. the current plan would have about 10ft rise up to the roof, the collectors, then back down and about 30 ft to the pool. I'll have to see if any of the collectors give any information on the flow path through the collector.

 

[Denwood]

Pentair 3hp variable would be no problem at all for 10ft rise, it would likely do 3 times that with no issues. You want parallel flow only...most cross flow can be converted to a single direction.

 

[retillist]

Just came across this thread. I have a Hotspot FPH system. It does heat the pool, albeit a bit slower than a solar heater would. I had trouble finding an installer too, but the person who ended up doing it is a sole owner of his own small HVAC company. I'd recommend looking for someone like that, who is still trying to grow their business, and doesn't mind learning about something new in the process. All of the large companies with lots of HVAC techs will just say no, because it's too unusual for them and they have enough business doing stuff they're familiar with.

 

[250]

I gave up trying to find someone and went down the solar route. No one called me back, and everywhere I walked into gave me one reason or another they weren't interested. Probably too many bread and butter jobs for them right now. I like the idea of it still, and I think this time of year would be when it was ideal. Still pretty hot during the day so the AC would be pretty active, but because the pool isn't covered, it sheds quite a bit of heat each night.

 

[u3b3rg33k]

another way out is to go with something easy to do yourself. like this unit:


self contained refrigeration, hot and cold tanks. you can provide your own titanium HX and just pump hot water through it. I'm sure it costs a pretty penny, but it's drop and go. no hvac tech required to modify standard equipment to do something else. get yourself a pump panel from blueridge company (or menards, yes, you heard me, menards sells prefab hydronic panels) and go to town.

 

[Balvar24]

It is done on commercial pools using specialized equipment. Unless the pool chemistry is meticulously maintained it usually ends in wailing and gnashing of teeth.

Run away.

 

[Denwood]

Just came across this thread. I have a Hotspot FPH system. It does heat the pool, albeit a bit slower than a solar heater would. I had trouble finding an installer too, but the person who ended up doing it is a sole owner of his own small HVAC company. I'd recommend looking for someone like that, who is still trying to grow their business, and doesn't mind learning about something new in the process. All of the large companies with lots of HVAC techs will just say no, because it's too unusual for them and they have enough business doing stuff they're familiar with.

I read your thread I think over at TFP....I really do love this system. From the thermodynamics sense it just makes a ton of sense, and likely improves AC efficiency over the air cooled condenser.

When we did our hyper efficient commercial building overhaul, one of the HVAC systems originally quoted used a heat pump system that could say cool one part of the building, while heating another. It was the most efficient option out there, but also the most expensive right now. I am 100% sure that the push to efficiency will have heat pump tech in every building as evidenced by the popularity of hyper heat systems air source heat etc. The tech will drop a lot in price as policy/need dictate demand.

 

[blustang67]

I'm curious if anyone has any experience with using a heat exchanger that pulls heat out of the refrigerant of the HVAC and dumps it into the pool? The one I'm looking at specifically is made by hotspot energy and got a feature plug on This Old House, but I'm sure there are variations on a theme out there.

Heat Recovery Pool Heater | Compare To Solar Pool Heater | HotSpot Energy LLC

I've been trying to find someone local to do the HVAC with not much luck. No one returned any of my phone calls, so I started walking into business and asking. The responses have been tepid to cold. One guy tried to talk me out of it saying I wouldn't like it, but I suspect they just didn't want to do it. Maybe someone here can fill in the gaps for me.

Thanks,

I bought a pool heater from hotspot energy. You pay for the unit and then have to hunt around for a HVAC/Plumber/Electrician to even install it. Took me 18 months after 3 different companies backed out. It cost a total of 5K to install. They sent me two control boards back to back that did not work, as I paid the technician by the hour to wait/sit/talk on the phone with hotspot energy. I asked them to reimburse me for the extra time I had to pay to troubleshoot two bad boards. This was June 2023, they did not respond or refund me money. In the meantime, (JULY 2023) the thermostat stopped working and goes from 100 to 40 in a matter of minutes. The blue plastic unit has all plastic fittings that leak. I added Teflon tape to the threads to try and get it to stop but am afraid of over tightening. If the unit turns on without the pool pump running for whatever reason, the entire unit heats up really hot and your AC stops working properly. Not to mention, if your AC needs to be replaced you can't just swap it over. Stay away from this product. I 100% regret it. Wish I had done a solar heater and not tear up my AC unit. I write this as my house is 82 and trying to cool down because of this **** product. HOTSPOT needs to do their own installs and back up their products. Every time it fails you are going to have to call an outside HVAC technician and eat the costs.

 

[u3b3rg33k]

I bought a pool heater from hotspot energy. You pay for the unit and then have to hunt around for a HVAC/Plumber/Electrician to even install it. Took me 18 months after 3 different companies backed out. It cost a total of 5K to install. They sent me two control boards back to back that did not work, as I paid the technician by the hour to wait/sit/talk on the phone with hotspot energy. I asked them to reimburse me for the extra time I had to pay to troubleshoot two bad boards. This was June 2023, they did not respond or refund me money. In the meantime, (JULY 2023) the thermostat stopped working and goes from 100 to 40 in a matter of minutes. The blue plastic unit has all plastic fittings that leak. I added Teflon tape to the threads to try and get it to stop but am afraid of over tightening. If the unit turns on without the pool pump running for whatever reason, the entire unit heats up really hot and your AC stops working properly. Not to mention, if your AC needs to be replaced you can't just swap it over. Stay away from this product. I 100% regret it. Wish I had done a solar heater and not tear up my AC unit. I write this as my house is 82 and trying to cool down because of this **** product. HOTSPOT needs to do their own installs and back up their products. Every time it fails you are going to have to call an outside HVAC technician and eat the costs.

it sounds like the controls were done improperly at a minimum - it should use the regular condenser + fan if the pool pump isn't running, either via relay, sail/flow switch, or thermostat, or it should call for the pool pump to run. Personally, I'd want a water-2-water unit for pool tie-in, it makes it much simpler to do (as mentioned above). as for the leaking fittings, try reconnecting them with pipe dope/sealant, or re-taping them, but make sure the tape is done properly (NOT at the very end of the fittings, that's incorrect).

 

[blustang67]

it sounds like the controls were done improperly at a minimum - it should use the regular condenser + fan if the pool pump isn't running, either via relay, sail/flow switch, or thermostat, or it should call for the pool pump to run. Personally, I'd want a water-2-water unit for pool tie-in, it makes it much simpler to do (as mentioned above). as for the leaking fittings, try reconnecting them with pipe dope/sealant, or re-taping them, but make sure the tape is done properly (NOT at the very end of the fittings, that's incorrect).

The unit has no way of knowing if pool pump is actually on or not. They are on different breakers. I am going to get it wired differently, however, there is no fail safe if the pump isn't running and or fails, it just heats up, warps the plastic casing, and the AC unit stops pushing cold air because the AC fan is shut off. The AC runs normal when it isn't trying to heat the pool. The controls were hooked up AS PER energy hospot. What it needs is an internal thermostat to shut it down if it gets too hot, but considering the thermostat that takes the pool temperature failed after 2 months I wouldn't have mush confidence in it lasting. When this POS stops working completely or my AC needs replacement I am ripping it out and putting in a solar heater

 

[u3b3rg33k]

The unit has no way of knowing if pool pump is actually on or not. They are on different breakers. I am going to get it wired differently, however, there is no fail safe if the pump isn't running and or fails, it just heats up, warps the plastic casing, and the AC unit stops pushing cold air because the AC fan is shut off. The AC runs normal when it isn't trying to heat the pool. The controls were hooked up AS PER energy hospot. What it needs is an internal thermostat to shut it down if it gets too hot, but considering the thermostat that takes the pool temperature failed after 2 months I wouldn't have mush confidence in it lasting. When this POS stops working completely or my AC needs replacement I am ripping it out and putting in a solar heater

sounds like it needs a simple relay or two to either
1: run the pool pump when there's cooling demand
or
2: run the condenser fan when the pool pump is off

I thought pool pumps ran all the time. is that not a thing? I can see why they wouldn't bother designing for pool pump failure. most ACs don't design for condenser fan failure (at least not the economy units). if the condensers are just in-line, a simple thermostat could run the condenser fan if the discharge temp from the pool condenser is too high. if it does fancy things like pump-down on the add-in condenser then the controls get more complex.

 

[nadogail]

Waste Heat should not be wasted, have seen it used to warm Boiler Feedwater, keep stock tanks from freezing and preheat the input to domestic hot water tanks.

 

[InsanePyro]

As goofy as this sounds look up "Linus Tech Tips" on YouTube, he recently did this to his home/pool

 

[P0234]

Not sure if it's been mentioned but our answer to a cold pool is a hot tub. We have a pretty shady yard and in the middle of summer we might hit 82 or 83 with the pool cover. Earlier or later in the season we swim until it hits the 60s. Just hit the hot tub for a few minutes before the pool and it's all good.

And in the winter a hot tub is awesome. So fun to sit in the tub on a rainy November day or after working in the snow.