Swimming pool for hvac well/cooling tower
 

I've been working on a plan in my head to retrofit my 2x 2ton hvac to watersourced condenser cooling using my pool as the water source. Additional benefit is I'll be heating my pool and may gain a couple of extra swimming weeks. I prefer the pool surface between 80-85F which is a bit warmer than most geo wells. My current plan would be circulate water to a buried 55 gallon barrel near the condensers. My heat exchangers would be 3/8 x50' copper rolls piped from the compressor liquid line. I could then either run it to the evaporator, or back through the condenser coils. If I do the latter could keep the outdoor fan on a pressure switch as a back up in case of pump failure. The draw back would be the extra resistance of going through 2 coils, and likely warming from warmer ambient air temp.

One benefit would be no outdoor fan motors, currently about 1 amp each. These will be replaced by one circulation pump switched by either compressor, or bypassed when the pool pump is already on. The main power savings would be heat exchange and sub cooling. I think a reduction near 3 amps each compressor, without the fans maybe a kilowatt each. Does this sound viable? Chances are I won't have time to trench water lines until cooler weather.

How big is the swimming pool? You can REALLY heat up a pool (even a large one) with this technique.

Steve

10,000 gallon. With a solar blanket on, the surface stays 80 overnight and gets up to 85 on a hot and sunny day. Without a blanket maybe 5-10 degrees less. My pool walls and floor are insulated with 3/4" R-board. We typically only use one 2 ton zone at a time, living down stairs sleeping upstairs. Seems like it could dissipate the heat overnight.

Dumping in enough btu to raise pool by 2-3 deg per day with blanket.

Sounds like you need to put a linear thermostat in the pool and use a PI controller to drive your thermal blanket drive motor - if it is automatic and not manual.

Worst case you would need to put a spray head in the pool to cool the pool thru spray evaporation.

If I put this together I'll probably keep the cover off during the summer months. I usually swim from April through October with the solar cover depending on rain which really cool off the water. Since we usually need some a/c in spring and fall this might help put a little extra heat in the water when we need it. I do have 4 deck jets which spray somewhat laminar arches into the water. They can cool the water a little, but too much aeration can through off ph.

I had a design to use our above ground pool as a passive cooler - basically running water to through coils with 12v fans via manifolds into my house and back to the pool. An engineer friend of mine warned of the effects of chlorine on the copper (?) I've not moved forward with the project until I find out the best material to use for such an idea. Something to think about.

Here's a compatible HX:

https://surpluscityliquidators.com/v..._TON_COAX_COIL

https://surpluscityliquidators.com/p...m/1/141194.jpg

The only hx tube material more chemical resistant than cupronickel is titanium. Turbotec makes a line of titanium-plumbed coax coil heat exchangers, the pool safe line. Needless to say, these are nearly impervious to corrosion, and fall out of DIY-budget range.

Just as a note, when using that particular exchanger as a condenser, it should actually be mounted upside down compared to how the picture shows it, with the connection that would then face down as the liquid line connection. Water flow should be opposite to refrigerant flow whether used as a condenser or evaporator, only exception is in a heat pump where the refrigerant flow reverses, at which point you have the water flow going opposite in the mode that is used more.

I was even thinking of a water cooled condensing coil for a cooling tower building. The ones I'm most familiar with could be opened and cleaned, but crazy heavy. Cooling tower water is often chlorinated but probably not to pool standards.
This could be worth while, my outdoor fan draws about 1.5 Amps@240v, 360 watts. If I can get enough water circulation without using too much power. Low speed on my pump should be enough. It might make more sense for its own pump that I can switch with the a/c contactor.This summer I ran the pump very intermittantly, mostly just before when we were in the pool, and a few times for a good cleaning. We saved a lot of kw without any water balance issues. The main benefit now would be extra pool heat. Late summer rains have cooled off the water too much for swimming, even though its been definitely warm enough for a/c.

If your main goal is saving energy, you can run the condenser tubing straight to the pool water and let mother nature do the rest. The simplest version of this would be merely submerging the tubing in the pool. A more modular version would plumb in as a thermosiphon, like this but mounted vertically (obviously adapted to your pool plumbing):

http://ecorenovator.org/forum/attach...103752_298-jpg

Even with the 55 gallon drum setup, the coil could be placed in the drum and plumbed to thermosiphon. An advantage to this idea: you could draw hot water out of the top of the drum and spray it in the air on its way back to the pool as a secondary cooling method.

With the large body of water acting as a buffer, the indoor-outdoor temperature split would be closer than you could achieve with an air-cooled condenser most of the time. However, the heat has to go somewhere. If you are dumping 4 tons of heat into the pool all day long, a secondary cooling system will be needed unless you like a hot swim.

Using less watts than a manufactured unit isn't too difficult, but in this case the least is the most, so to speak. The more passive and overbuilt your design is, the better the odds are stacked in your favor. Be creative and criticize your own choices before you commit.

Hey that's my PVC exchanger :) It didn't work for high-temp/high-side compressor HP water heater BUT I'm glad I didn't throw it away - you gave me hope to use it in some way. I ended up building an all copper HX for hot water via HP app that DOES work. Just finished the pool water experiment and that is a success as well. Anyway, cool, I'm hoping to use that damn PVC HX for something!- [go brain go]

Doh, you got me! How much do I owe you? Or may I just be forgiven? @sorry I didn't ask permission first.

For the record, your hx design is a proven winner. Your solid copper one is a lifer. The one in the pic can be finished leak-free. Both are dependable warriors worthy of imitation.

BTW, what is this forum's stance on copyright law anyway?

PVC HX Final Version
 

LOL - I really don't care - it was kind of a surprise and, to be honest, I was a bit flattered. Here is the final version after trying all kinds of seals and epoxies - I had it threaded and I used these twist on rubber seals.I thought it was a winner. It stayed tight for about an hour then just started 'seeping' a little which of course is not going to work - thus the copper version. As per your suggestion, I do believe it would be a great HX in a submersed situation such as a pool (hp to pool water - to heat pool). However, I'm not that interested in heating my pool water so I think I'm going to adapt it to use on my sailboat. I'm thinking of putting long vinyl hoses in/out and dropping it overboard while docked or resting and using a 12V pump (in a closed loop) to circulate cool water through a small evap. coil to help cool the cabin. At the very least, there is still hope for the PVC model in some application I'm sure of it :) Thanks for posting - I enjoy your input and suggestions.

http://ecorenovator.org/forum/attach...er-hx_last-jpg

Wow, it still lives! I figured it ended up an orphan or worse.