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graypenguin 11-28-2010 11:05 AM

Water cooled air conditioners / water heaters
Does anyone know how hot the water coming out of a water-cooled air-conditioner gets? I was thinking it might be a good idea to run the "heated" water through a water tank that has the heat exchanger option.

I would think that it would be at least 15 to 20 degrees hotter coming out then going in, so maybe 90 degrees....

sailingdog 11-28-2010 11:39 AM

No, it doesn't get that warm. Water has a very high heat capacity, and it only heats a few degrees above ambient when used in a heat exchanger for an AC unit. Certainly not at a temperature where the difference would be useful to heat water.

I'd point out that the additional resistance of the heat exchanger coil in the hot water heater would also put a strain on the raw water pump for your A/C system, and that most are undersized as it is and would lead to them failing sooner.

deniseO30 11-28-2010 02:40 PM

To get "hot" water off of a AC, refrig, or central ac unit,water or air cooled, One would need a heat exchanger on the high temp high pressure line right off the compressor.(the discharge line before it goes into the present condenser) That line is always well above 100 degrees when the comp is running. Most marine units under 24,000 btuh are too small to make enough hot water to be useful by use of a discharge gas H/X

The existing condenser (water or air) would become secondary but still necessary.

On larger water cooled units using geothermal, closed loop or well water there is a control that modulates the flow of water through the heat exchangers that keep the operation pressures constant. This modulating water valve is very common on larger units, it controls the water flow rate via the pressure of the refrigerant. In general, of any type unit will heat the condensing water only about 10 degrees, unless in reverse cycle, then then it would be 10 degrees lower.
Metrex Valve: Water Regulating Valves for HVAC Commercial, Marine&Nuclear

For any larger unit a discharge gas h/x is still the way to heat water and it requires cutting into the refrigerant lines and all the usual hvac routines to install it.

You would get more heat, from a diesel inboard H/X actually. or even a solar collector instead a little 16,000 btuh or so boat a/c.

Work vs return? not worth the trouble.

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