Can someone explain to me the proper behavior of the air conditioning circulation pump?   On my 575 its installed under the sole near the companionway.   I have a manifold setup that has slightly changed from the delivery as I replaced all the seacocks and the strainer.  The support layout for AC is the same with the 3 salon and aft air conditioner feeds/returns while the forward AC units are served forward.   I also insulated the floor and removable access hatch which reduced the originally intolerable pump noise by 90%.    

The problem is that the pump never seems to shut off when using it for AC or reverse heat.  When the breakers are flipped it goes on.   When the AC units have either heat or cold temps at the thermostat set levels, it still seems to be on. 

Is this normal?   You would think that if none of the AC unit compressors was running that it would not need the circulation pump running.    If the compressor kicks in, then it seems logical to signal the pump to start up.   Not happening.

 I've had the boat for 7 years and never really noticed this since we don't use the AC except for early season heat and the hottest of summer days. 

I have a 458 with three factory supplied A/C units installed. There is also, what sounds like a similar pump/manifold setup with one Dometic circulation pump under the floor. My pump does not run continuously - it on,y comes on when signal,Ed to by one of the AC units. It can seem like it’s running continuously during the hot days down here but when things cool down at night the AC’s and the pump will shut down.

Maybe one of the control boxes wiring is wrong? Or perhaps a setting on one of the thermostats? Don’t know how far you’ve delved into those settings but there’s a lot of them that can be changed. In either case maybe you can troubleshoot by trying one unit at a time to see if one of them is triggering the pump when you flip its breaker. Does the pump go on if you only turn that breaker on and no AC’s?

Sounds like our air cond system is the same as your - which makes sense. I am fairly sure our cooling feed pump runs continuously only the individual air cond compressor units stop and start as they reach the set point temp. I guess all four air cond compressors would need to stop at the same time for the feed pump to shut down if the system was set up like that. If one air cond unit is still running that unit still needs cooling water. The feed pump obviously supplies all air cond compressor units. I guess you could test the system but just running one air cond compressor and close that area (cabin) off so the unit would reach the set temp and shut down. If the feed pump still runs I guess the answer is no the feed pump runs continuously when any or all air cond compressors are on. Good idea to sound insulate the area where the feed pump is.   

Cheers

Duncan

We did it by ourselves and fit a pump relaybox ,2 to 6 units can connected,from Climax marine easily to Google.

When one of compressors starts up ,and only the compressor not the units himself, the AC waterpump starts automatically and stop when none is running.

I am very happy with it: only defect is that the water pump sometimes doesn't self prime after sailing/heeling, and it resulted in a burnt water pump before i learnt to check the priming after navigation...It is more an installation issue than an issue of the aircon itself. I can also use it on batteries with some caution (one heat-exchanger only, and not to the maximum power)...

...just for the record...

Thanks for all the inputs...   I'll be running some tests when I get to the boat again and will post my findings.     I have 4 AC breakers.   One for the circulation pump and 3 that control the 1 forward, 1 aft, and 2 salon AC units.   I assume this is a standard 575 setup.   I will be checking:

1.  When I flip the circulation pump breaker, but not the others, does the pump run?

2.  If not,  then does flipping just one of the other breakers cause it to come on?

3.  If so, which one?

4.  If the answer to (1) is yes,  then I guess I need to check what the pump wiring / signals are supposed to do.  Maybe (to the point raised) there is a setting that tells it to shut off if the other AC units are not on.    I'll have to find the pump manual and the manual for the AC units to do this.

That’s the same breaker arrangement that I have. If the boat is relatively cool, I.e., all temps are below the thermostat settings, when I turn on all of the breakers, nothing happens with the pump. It will only turn on when a thermostat signals an AC unit to turn on. When that happens, the pump turns on first for a few seconds before the AC compressor starts. The opposite happens when a compressor shuts down - the pump will continue to run for about 5 seconds before it shuts down. It stays off until a thermostat triggers it on.

Good luck.

Mike

For years the big central AC pump came on only upon demand from an AC unit. Then it started running continuously. Annoying. 

Leon,     I just arrived on my boat and was planning to look at it tomorrow.   The P-12 vs P-11 info came from a manual I found on the internet.   I need to verify model, manual, etc.  first before doing anything.     I know I have the AC manuals, but not sure about the pump.   Will let you folks know what I find out.