FPH AC condensor heat exchanger alternative from Aliexpress

bluedolphin

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Hello, Hotspot Energy has a line of heat exchangers (FPH series) that transfers heat from your AC condenser coil to circulated pool water. Their solution costs (~$1,850 made in China) in comparison to a very similar looking models found at Aliexpress ~$300 $450 depending on sizes.

One example is the Gimleo model: MHTA-5 for ~$430 (made in China). 58,000 BTU/h

Has anyone purchased and installed a similar model on Aliexpress before?


Hotspot FPH3 model
52500 BTU/h
1631553091636.png

Gimleo model MHTA-5
58,000 BTU/h

1631553104568.png
 

cowboycasey

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That is the exact same stolen design/part from them and they are selling it illegally.. the problem being is it is just fine for them to do this and the US has no recourse...
 

cowboycasey

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Ohh, I know it is... almost everything is.. :)
 

bluedolphin

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@swamprat69 After I posted this I checked and ya... the HotSpot cost ~$1,850 is for the whole system with warranty. Titanium heat exchanger, thermostatic controls (I think that means their controller / box), sensors, and the heat recovery valve kit. Plus $200 for a pressure equalizer and $100 shipping. Not just the heat exchanger. Although I am curious to find out how much for everything but without the heat exchanger. The 17KW (58,000 BTU/h) heat exchangers through AliExpress with shipping are around $320 after you shop the prices.

 
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BowserB

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Why are you considering this product? What is your objective? I've looked into these casually, and the numbers don't work for me. The payback in savings in natural gas looked like it might take 25 years to break even--if ever, since I don't know how long the thing will last. The times when the most heat would be needed would be when the A/C is running least. What's the installation going to cost? Additional refrigerant probably required, and the price of that has gone up nearly 10 times recently in some places. This is one of those things that could make sense in a new home and pool built at the same time, as it would be just incremental cost, and the layout could take everything into account. You could even have the A/C condensate routed to the pool instead of the sanitary sewer in order to compensate for evaporation. Of course that would be cool water being added to the pool.

We heat our pool some in the spring and fall and heat the spa all year. Our gas bill ranges from $35 to $60. We have a gas range, gas furnaces, and a gas fireplace, in addition to the 400,000 BTU Pentair heater. And 52,000 btu's from the heat exchanger device? I don't know how big your pool is, but I hope you're very patient. My 400k btu heater raises the temp of the pool about 1 degree in 25-30 minutes, depending on ambient air temperature. It heats the spa alone maybe 10 degrees in 15-20 minutes, so no planning is necessary for a heated spa. But that's with nearly 8 times the heating power of the A/C heat exchanger.
 

bluedolphin

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@BowserB all good points. We run AC, 12 months out of the year. There may be a few days or weeks that we wont run AC. Using a heat exchanger will allow the AC to run more efficiently. Believe it or not, the pool temp at hotest time of year is around 87deg naturally. Apparently I am told that is too cold!!! The goal is to get the pool temps to around 95 deg 24/7,for as many months as I can. We would use a few of the round pool cover discs to help hold in heat at night.

 

ps0303

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Why not just buy a real pool heater? The BTU of what you are talking about isn't much.
 

jseyfert3

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Why not just buy a real pool heater? The BTU of what you are talking about isn't much.
I haven't run any numbers, but the OP seems like the perfect application for this. Desires year-round pool heating. Requires year-round use of the AC. It may not work as the sole source of desired heat but it should certainly make a difference in the water temps. Also a "real" pool heater costs money to run. The heat from the AC is already paid for but wasted normally.

@drglanton installed one of these in Georgia and last I knew was quite happy with it. Still working well @drglanton?
 

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BowserB

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@BowserB all good points. We run AC, 12 months out of the year. There may be a few days or weeks that we wont run AC. Using a heat exchanger will allow the AC to run more efficiently. Believe it or not, the pool temp at hotest time of year is around 87deg naturally. Apparently I am told that is too cold!!! The goal is to get the pool temps to around 95 deg 24/7,for as many months as I can. We would use a few of the round pool cover discs to help hold in heat at night.

Here in southeast Texas, 40 miles from the Gulf of Mexico, A/C is a 12 month a year requirement, too, thanks to high temps and high humidity. And yes, I do believe your "untreated" water temp of 87...AND that to some people that is just too cold. One person in our household considers 90 or 91 the minimum comfortable pool water temperature. Our morning water temp in July and August is typically 87 or 88--lower when we have rainstorms. A couple problems I see with the solution you're considering. The first, as I mentioned before is that 55-60k btu is not much heat. The other problem is that any savings in your A/C is going to be minimal and probably nonexistent at night when 87 degree water is probably warmer than the air. Also, to have the benefit of the A/C heating the pool water 24/7, you're going to have to run both your A/C and your pool filter pump 24/7. I'm pretty sure when all is said and done, you're going to use more electricity; not less.

I am a retired CPA, former financial analyst, former corporate controller, and also former I.T. consultant. I am big on technology and energy efficiency. I've investigate solar for electricity once a year for the last four years (13.5 yr break even doesn't work for me.) I'm looking into a whole house dehumidifier to help with indoor comfort without running the A/C at low temp settings (still working on that one, but it doesn't look good!) The thing that stops me again and again is the numbers. My whole working career was numbers. Return on investment, payback, false economies, good money after bad (aka "sunk cost")...when you really run the numbers, a lot of theoretically good ideas don't hold up. I've looked into the concept you're looking at, and for me, like solar panels and the Tesla Wall battery, it doesn't pass my financial tests.

BTW, if you would fill out your signature with a full description of your pool and equipment (see mine as an example), it will help others here to help you and give useful advice.
 
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borjis

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AliExpress. I've had way too many bad experiences w them. They do not honor warranties, buyer beware. But they'll be happy to take your money.
 

jseyfert3

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Here in southeast Texas, 40 miles from the Gulf of Mexico, A/C is a 12 month a year requirement, too, thanks to high temps and high humidity. And yes, I do believe your "untreated" water temp of 87...AND that to some people that is just too cold. One person in our household considers 90 or 91 the minimum comfortable pool water temperature. Our morning water temp in July and August is typically 87 or 88--lower when we have rainstorms. A couple problems I see with the solution you're considering. The first, as I mentioned before is that 55-60k btu is not much heat. The other problem is that any savings in your A/C is going to be minimal and probably nonexistent at night when 87 degree water is probably warmer than the air. Also, to have the benefit of the A/C heating the pool water 24/7, you're going to have to run both your A/C and your pool filter pump 24/7. I'm pretty sure when all is said and done, you're going to use more electricity; not less.

I am a retired CPA, former financial analyst, former corporate controller, and also former I.T. consultant. I am big on technology and energy efficiency. I've investigate solar for electricity once a year for the last four years (13.5 yr break even doesn't work for me.) I'm looking into a whole house dehumidifier to help with indoor comfort without running the A/C at low temp settings (still working on that one, but it doesn't look good!) The thing that stops me again and again is the numbers. My whole working career was numbers. Return on investment, payback, false economies, good money after bad (aka "sunk cost")...when you really run the numbers, a lot of theoretically good ideas don't hold up. I've looked into the concept you're looking at, and for me, like solar panels and the Tesla Wall battery, it doesn't pass my financial tests.

BTW, if you would fill out your signature with a full description of your pool and equipment (see mine as an example), it will help others here to help you and give useful advice.
You have a lot of good points but the real question is have you run actual numbers? You say it doesn’t pass you financial tests so I would assume you have? What sort of numbers are we looking at?
 

bluedolphin

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@BowserB Thank you. Signature filled out. I understand where you are coming from when you say good money after bad and ROI. There is a lot of corruption and snake oil in the solar, wind and electric vehicle industries. I think a small scale solar PV system $5kw, grid tied but !!!no batteries!!! might be more practical. Or even skip the grid tie and the losses associated with converting DC electric to AC with an expensive inverter. Use some solar panels to power some DC powered equipment, like a DC powered pool pump, or a AC/DC powered Air Conditioner unit.

For my pool heating project, basically it's not getting much use because wifey says its too cool. So I have money tied up in the pool build and running/maintaining the pool with little use. So I'd like to heat the pool, an adequately sized heat-pump would do the job but the cost for the equipment and to run it is what deters me. At half of the cost, with the heat exchanger I could capture some of the heat, run my variable speed pump with longer run times at the lowest specified flow rate by the heat exchanger. Throw a few of those round pool cover discs over the pool at night to help keep the heat in hoping for a pool temp of low 90's for a few months out of the year.

If I can get a better price for the system then maybe the numbers work out for the SW Florida part of the country that we live in?
 

BowserB

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Hi again, Blue. I appears you have no heater now, and that's your need. I don't see mention of a spa in your signature, so what I'm about to show may be less relevant. Like your situation, my wife likes very warm water. Yesterday afternoon 3:45pm (CDT), we decided a bottle of chilled Prosecco in the spa (approx 350 gallons) would be nice. Air temp at that moment was 97 degrees. Water temp was 88. I set the water valves so all return was to the spa and about 95% of the suction was from the spa (wife likes the sound of a little spillover). Set pump on manual and 2300 rpm and turned on the Pentair Mastertemp 400 heater. Ten minutes later the temp in the spa was 96. That was with 400,000 btu heat running and 95% of the water recirculating through the spa and heater. Your proposed A/C heat exchanger at 55,000 btu in theory, being 1/7th the heat potential, would presumably take seven times as long to heat that 350 gallons. 70 minutes? Just for the spa? 12,335 gallons would take 35 times as long? 40 hours?

My point. Even if it works, it's probably not going to work very well.

BTW, if you're really using pucks to chlorinate your pool, you're eventually going to have a CYA problem, too.
 
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JoyfulNoise

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These units are basically a "poor man's heat pump" ... For all the money you would dump into the project you could buy a 75kBTU heat pump that would probably work more efficiently. And I agree with @BowserB , this is not intput-energy-free heat, it's going to cost you to extract it. If you want year-round accessible and relatively-free heat, then put in a solar heating installation.

One has to remember that these units require you to do significant modifications to an HVAC unit that most HVAC guys are not going to be comfortable doing. So it will void any warranty you might have (no a huge loss, I know) and then finding someone to fix your A/C when it goes down might result in them taking one look at the modification and saying, "NOPE! Not gonna touch it ..." One also has to be very careful with how much heat energy you take out of the refrigerant with an external heat exchanger. AC compressor units have their own set of HI/LO operating pressure and temperatures designed around the specific setup of the heat exchanger and expansion coils (the A-coils inside your air handler). Pulling too much heat out of the refrigerant could cause it to liquefy and then that liquefied refrigerant could hit the compressor and destroy it. The AC has an expansion valve (either thermally controlled or electronic) to help meter the refrigerant but if you push the unit too far off its proper operating point, you could cause a really expensive failure or stress the unit into premature failure. Seems like a whole bunch of what-ifs and expense for not much return.
 
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JoyfulNoise

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And, more simply, buying random junk of AliExpress will probably result in you getting a vintage pair of Hello Kitty socks for your $300 and no recourse for getting your money back ... and then 10,000 emails asking you to "rate your experience" ... oh wait, that's Amazon and Facebook Market ...
 
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jseyfert3

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Hi again, Blue. I appears you have no heater now, and that's your need. I don't see mention of a spa in your signature, so what I'm about to show may be less relevant. Like your situation, my wife likes very warm water. Yesterday afternoon 3:45pm (CDT), we decided a bottle of chilled Prosecco in the spa (approx 350 gallons) would be nice. Air temp at that moment was 97 degrees. Water temp was 88. I set the water valves so all return was to the spa and about 95% of the suction was from the spa (wife likes the sound of a little spillover). Set pump on manual and 2300 rpm and turned on the Pentair Mastertemp 400 heater. Ten minutes later the temp in the spa was 96. That was with 400,000 btu heat running and 95% of the water recirculating through the spa and heater. Your proposed A/C heat exchanger at 55,000 btu in theory, being 1/7th the heat potential, would presumably take seven times as long to heat that 350 gallons. 70 minutes? Just for the spa? 12,335 gallons would take 35 times as long? 40 hours?

My point. Even if it works, it's probably not going to work very well.

BTW, if you're really using pucks to chlorinate your pool, you're eventually going to have a CYA problem, too.
And if I want to sit in our spa, I open the cover and get right in, no waiting, even in the middle of winter surrounded by snow and ice. Point being, different devices work differently.

But what I’m really curious about is your financial analysis that made you not want to get this. I’m an engineer, I like to see numbers. And yes, one of my teachers drilled total lowest lifecycle cost into my head. I’m curious about getting one of these units myself in the future, so I will do an lifecycle analysis at some point.

But in the meantime yes getting it installed is a hassle, but the few threads I’ve seen where people got one installed it made a noticeable difference in their water temp. And while it may not be completely free energy it would seem with a VSP tied to the system (so the pump doesn’t run 24/7) the amount of energy needed would be minimal. So it could likely be considered free energy for all practical purposes, except of course the initial purchase price.

Funny enough the exact best use case of this device is exactly your don’t wait to use, only for pools. If you have a regular heater you don’t normally run it 24/7, so you need to plan and use the heater. But this recovery device you’d just run 24/7 because it’s free or almost free heat, so your pool is warmer 24/7.


One also has to be very careful with how much heat energy you take out of the refrigerant with an external heat exchanger. AC compressor units have their own set of HI/LO operating pressure and temperatures designed around the specific setup of the heat exchanger and expansion coils (the A-coils inside your air handler). Pulling too much heat out of the refrigerant could cause it to liquefy and then that liquefied refrigerant could hit the compressor and destroy it.
Temps of the condenser won’t be a problem, any pools temps are well within the operating temperature range of an AC unit.

Also I need to review my mechanical engineering textbooks but the purpose of the condenser is to condenser the refrigerant. Definitely want that to be a complete liquid before going to the expansion valve. The whole reason heat pumps work is the phase change of the refrigerant going from a liquid to a gas.

And when you buy the system from Hotspot, not bits and pieces (which I don’t recommend) the condenser size is matched to the condenser size of your AC unit. And if I believe if needed also a small accumulation tank. This is done to not change the amount of refrigerant used, which could indeed cause issues. There’s a three way valve added and if your pool calls for heat the refrigerant is pulled out of the AC condenser and directed into the pool condenser. If the pool doesn’t need heat it pulls the refrigerant out of the pool condenser and routes it through the air cooled condenser as normal.

I do agree that if the OP has south facing room and doesn’t object or have restrictions against it that solar heating would be a better way to go to increase the average pool water temp. I’d really like to do that myself, but there’s some covenants about it in our neighborhood. That is why I was considering the Hotspot instead.
 

JoyfulNoise

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I do agree that if the OP has south facing room and doesn’t object or have restrictions against it that solar heating would be a better way to go to increase the average pool water temp. I’d really like to do that myself, but there’s some covenants about it in our neighborhood. That is why I was considering the Hotspot instead.

Many States (ymmv) have solar-access laws, ie, HOAs, neighborhood covenants and municipalities are legally barred from interfering with homeowners installing solar devices (heat or PV). They can ask you to please make it look nice but even then they can not use aesthetics arguments to block an installation. I routinely threaten my neighbors that I plan to install a huge ground-based array in my front yard with the panels angled so as to beam reflected light right at them … the snakes and lizards need some shade so why put them on the roof 🤷‍♂️. They laugh uncomfortably when I tell them my plans because they are not sure how serious I am ….
 

swamprat69

Well-known member
Mar 30, 2019
581
Las Vegas, NV
Another consideration to take account of is the useful life of an AC condensing unit. Normally 15-20 years IF installed correctly AND serviced/maintained regularly. So you install FHP on a 10+ year old condensing unit that the compressor (most expensive part/repair) is out of warranty No problem. The compressor fails in year 13 and you need to replace the condensing unit and possibly evaporator. Now you pay to have a new AC installed and adapted to use FHP, but probably void the warranty of your new expensive AC. If it was not installed correctly and you have any problems from the start, you might find a lot of finger pointing and no resolutions to any problems that develop.
 

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