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Old 06-05-2012, 17:06   #1
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Two A/C Units with one pump?

Is it possible (and good practice) to run two separate air conditioners with one water pump? Is it also possible to use one thermostat for two units?
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Old 06-05-2012, 17:33   #2
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Re: Two A/C Units with one pump?

I run 3 15000 BTU units on one seawater supply pump w/o problem.
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Old 06-05-2012, 17:41   #3
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Re: Two A/C Units with one pump?

I agree, I run a 12,000 and a 16,000 BTU units with only 1 seawater pump but each unit has its own thermostat...no problem
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Old 06-05-2012, 17:48   #4
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Re: Two A/C Units with one pump?

Can't argue with experience (as above). My only comment is that the laws of thermodynamics exist - that is, the heat transfer is a function of both the volume of water and the temperature of the water used to transfer heat. Two units may work well on one pump but you effectively cut the volume of water in half (actually less because of flow resistance) thereby decreasing the efficacy of heat transfer. If one pump works, two will work better - it depends on your needs, comfort and ambient temperatures.
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Old 06-05-2012, 18:13   #5
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Re: Two A/C Units with one pump?

My A/C specifications list a minimum flow rate well under half of the capacity of the associated March pump.

Seems to me that indicates the pump could easily supply two A/C units of the type currently installed.

I would think if the pump capacity was somewhat greater than the two unit's needs combined then things would work fine.
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Old 06-05-2012, 18:26   #6
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Re: Two A/C Units with one pump?

Quote:
Originally Posted by four winds View Post
My A/C specifications list a minimum flow rate well under half of the capacity of the associated March pump.

Seems to me that indicates the pump could easily supply two A/C units of the type currently installed.

I would think if the pump capacity was somewhat greater than the two unit's needs combined then things would work fine.
The actual flow rate/volume isn't just a function of the pump rated capacity - it is also limited by the size of the plumbing and all elbows and other restrictions, all of which must be considered as a system.

Buying a higher capacity pump in a system limited by small hoses and long runs may be a waste of money. It sounds like the consensus is it works which is the only important thing!
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Old 06-05-2012, 18:40   #7
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Re: Two A/C Units with one pump?

I agree about the additional factors regarding flow.

That's why I use the phrases "well under" and "somewhat greater".

Couldn't qualify those facets of the scenario more accurately. But I suspect that the flow rate of mine being greater than double the need, it could be approaching the point of diminishing returns. Considering the surface area of the heat exchanger itself is also a factor.
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Old 06-05-2012, 18:47   #8
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Re: Two A/C Units with one pump?

I run 2 Cruisair A/C units off one pump, no problems and I believe matches the installation literature that came with my units. I'm not sure you can run two units off of one thermostat, though.

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Old 06-05-2012, 19:02   #9
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Re: Two A/C Units with one pump?

From Cruisair
When more than one air conditioning unit is served by a
single pump, a separate pump relay is used.
http://www.boatelectric.com/L-0242-PUMPS.pdf
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