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Using Water to chill a condenser

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tonyzarger

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Discussion starter · #1 ·
I apologize in advance for the long story. When we moved into our home 30 years ago, it had gas fired hot water baseboard heat and no air conditioning. I wanted air conditioning. Our domestic water supply is from a well that has 12 psi natural pressure at ground level, and a water temperature is 52-deg F. I added a secondary tap off the well casing, and ran an 1.25" line into the house. I purchased two coils that were designed for chilled water, and I have successfully used this to cool my 3800 square foot home for 30 years. It is getting to be time to replace the air handlers and the coils and there are several design issues I wanted to fix.

1. While this systems cools well, it does not reduce the humidity enough. The delta temp at the coil is not high enough.
2. Because this was a retrofit project, I ended up putting one cooling coil in the attic to support the second floor cooling. I have always worried about having water leaking in the attic, and that I have to blow the water out of the lines in the winter. So my preference is to switch to refrigerant based cooling instead of water.

My question is, do they make residential HVAC systems where I could use a water based heat ex-changer instead of air to cool the condenser unit. This would enable me to use a much smaller compressor, and be able to run the coolant cycle at lower pressures and temperatures. Everyone wants to sell me a full blown heat pump, which I don't think I need. I have seen a "This Old House" episode where they used the swimming pool water and a heat ex-changer to cool/condense the refrigerant, but I have not be able to find a manufacturer willing to explore this.

thanks in advance for the help!
 
#3 ·
You are looking for what amounts to a geothermal household system.
Both climate master and water furnace make excellent units.
You'd also likely save on heating costs in the winter if you found a way to dispose of the used water
 
Discussion starter · #7 ·
pecmsg,
Originally the dump was directly to my pond. About 10 years ago, I rerouted it to my shop/out building, run it through a couple of coils, and now my shop is air conditioned as well.
 
Discussion starter · #8 ·
We live in Michigan and the natural gas here is pretty cheap, especially compared to electricity. Also since my heat is a gas fired hydronic boiler, if the power goes out, I can still heat my house with a car battery and an inverter to power the furnace circulator.
 
#10 ·
You can also fit a standard AC with a desuperheater. The better quality plate exchangers are expensive though. Strongly advise cupronickel with any option using a salt pool.
 
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#11 ·
tonyzarger said:
....This would enable me to use a much smaller compressor, and be able to run the coolant cycle at lower pressures and temperatures.
Click to expand...
It don't work that way. The compressor would be the same size weather it's water or air cooled. You may have meant the "condensing unit", and if so, then yes, it would be physically smaller. Also, generally speaking, your pressures/temperatures would need to be about the same also.

Water cooled condensing units for refrigeration systems do exist. You could certainly use one of those to do what you want. You would need someone who's good with commercial hvac and refrigeration in order to get one installed. R410A (which is the refrigerant that most residential air conditioners use these days) probably won't be an option, therefore whatever evap coil you get will probably need to get converted to run on R404a or a R22 substitute. Also, these things aren't setup to work with 24V residential thermostats, and not just anybody would be able to figure out how to make it work. Not really that difficult or complicated, just different than what most residential guys normally have to deal with.

It can be done. Finding someone to do it will likely be the hardest part.
 
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Discussion starter · #12 ·
Ammoniadog,
thanks for that. I grew up in a plumbing and heating business and I am familiar with the thermostat issue. I agree that the condensing unit would be smaller when using water as the coolant. I have even looked at the plate type heat exchangers to perform that function. I have studied the phase diagram for several of the refrigerant types, that is how I concluded that using 50 degree-F water to cool the refrigerant would allow me to reach the saturation/condensation line at a lower pressure and this could potentially reduce the required size of the compressor. I also agree that this is not a typical application for residential work, and I may need a commercial HVAC designer to be involved. Silly me thinking I may be able to get something off the shelf.
Thanks again for the feed back.
 
#13 ·
tonyzarger said:
I have studied the phase diagram for several of the refrigerant types, that is how I concluded that using 50 degree-F water to cool the refrigerant would allow me to reach the saturation/condensation line at a lower pressure and this could potentially reduce the required size of the compressor.
Click to expand...
Most condensing units are designed to operate with a condensing temperature of around 85 degrees. Doesn't matter if it's air or water. On the water cooled units, there is a water regulating valve that will slow the water down to keep the refrigerant discharge pressure where it needs to be, so you really aren't gaining anything by having cold water. Air cooled condensing units that have to run in the winter (i.e. most walk-in coolers/freezers) work the same way. They have head pressure controls to keep the pressure up. Otherwise they won't work right. Just because it's zero degrees outside, it doesn't mean that the unit will be saving all kinds of money on the electric bill.

I would recommend recalibrating your phase diagrams to 85 degrees and then see what kind of numbers you come up with.
 
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#14 ·
I had a P&D job in NJ and we used the discharge water for a 'water feature' in the back yard. It was a really nice arrangement of statures and water cascades about 6' tall and maybe 10-12' diameter. The water drained away into a wooded area. I guess the top froze or something because one time when I got there for a no heat call they showed me their 'ice sculpture'. When the heat pumps were running the water sprayed straight up probably 5' higher that the water feature and in very cold weather it all froze into a gigantic ice-sculpture. It was pretty cool looking.

We also did one at a large estate-type property in Philadelphia - actually past City Line Ave. so maybe Roxboro. The discharge water supplied antique fountains in the back yard. They (obviously <g>) flowed at random intervals - which somehow delighted the woman. I never saw it in the winter but I imagine it also froze over in really cold weather.


PHM
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pecmsg said:
But where’s the Dump?
Click to expand...
 
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Discussion starter · #15 ·
ammoniadog,
That was very useful information. that is also the difference between knowledge and experience. I will study what happens, if I constraint the condensing temperature to 85 degrees. That will definitely change the balance a bit. Thanks!
 
#16 ·
Maybe you should put down your pencil and crumble up that sheet of paper?

Why don't you address the issues separately - which is how they should best be addressed anyway.

Design your new hydronic cooling system along the same lines as the one you are presently happy with. And then design your dehumidification system as a separate entity. Leave the cooling that you already know you like as it is and just add a whole-house dehumidifier.

Otherwise you are adding horsepower and complication that could both be easily avoided in your case.
 
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#17 ·
Hold on now, if you lower condensing temperature/pressure you will gain in capacity.
One only has to look at a compressor proformence chart to see that.
I'll use this Copeland CRN5 as an example. Was quite popular back in the day.
Can be used for A/C or medium temperature refrigeration.
Look how your capacity goes up as the condensing temperature goes down.
 

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#18 ·
Your power consumption also drops as your compression ratio decreases.....although may amount to nickels per month in this case.

I agree that this is trying to reinvent the wheel in a very expensive manner that is likely to not see the ROI that might be expected, especially if it breaks down.

Sent from my SM-G965W using Tapatalk
 
#19 ·
VTP99 said:
Hold on now, if you lower condensing temperature/pressure you will gain in capacity.
One only has to look at a compressor proformence chart to see that.
I'll use this Copeland CRN5 as an example. Was quite popular back in the day.
Can be used for A/C or medium temperature refrigeration.
Look how your capacity goes up as the condensing temperature goes down.
Click to expand...
Yes, but notice how the numbers on the left side of that chart don't go down to the 52° water that we have to work with. There definitely are savings to be had if the unit can always run at a constant 80° condensing temp vs. having to float up to whatever the outside air temperature is though.

:cheers:
 
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ammoniadog
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