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Old 08-23-2019, 08:17 PM   #1
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Water pump for AC, newbie question

We've just graduated from sail and a few years down in Central America without AC. Now we have the space and power needed for AC and want to replace the current, ancient, AC systems.

I've been looking at the EnviroCool 'Self-contained Air Conditioning System' and it looks like it would be a breeze to install. The one question I have is if the 'optional' (not included) salt water cooling pump is automatically controlled/powered by such self-contained units ? IOW, does the power to the pump come on when the AC unit thermostat powers up the compressor ?

The ancient systems we are replacing have the salt water pump on continuously when the AC is on, even when the compressor isn't running, and that seems like a real waste.

Thanks.


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Old 08-23-2019, 08:21 PM   #2
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My marineair unit cycles the pump with the compressor. If that helps.
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Old 08-23-2019, 08:49 PM   #3
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Usually it's selectable in the thermostat programming. Its either on when you turn on the AC or comes on 1 to 5 seconds before the compressor starts. Most older units are that way where its through the thermostat or with mechanical thermostats, it was a switch within the control box.

Not sure why a water pump would be optional, it's either air cooled or water cooled.

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Old 08-23-2019, 08:55 PM   #4
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I think you are talking about one of the Dometic units. Yes, the sea water pump gets its power from the main unit's controller, which turns it on and off. If water flow is obstructed and it can't cool, it will shut it down with an error code, etc.
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Old 08-23-2019, 09:53 PM   #5
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It depends on the control panel on the AC unit. Most will at the minimum, have some sort of connection for a pump, either a set of "dry contact" terminals, a direct connection for the pump on the board, or a signal output for a pump relay. You'll need to check the manufacturer's instructions for the particulars for the unit you're using. Since your OP indicates 2 units, you'll need a pump relay to facilitate running the pump on a call for cooling from either/both units.
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Old 08-24-2019, 07:16 AM   #6
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"Since your OP indicates 2 units, you'll need a pump relay to facilitate running the pump on a call for cooling from either/both units."

The plan B option is a pump for each Air cond, so when one eats weeds or a jelly the vessel still has some conditioned air.
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Old 08-24-2019, 07:32 AM   #7
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Its an AC compressor and an AC pump, so have it come on when AC compressor comes on.
Or have it come on when the air-handler blower comes on.
My older Cruisair system was setup to start the water pump first with the inside fans, then turn switch to next position to add in the compressor.
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Old 08-24-2019, 09:30 AM   #8
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When in the tropics are both ac systems off at the same time? And for how long? You have to balance the savings in power from shutting down the seawater pump against the cost and complexity of having triggers and relays to turn the pump and compressor on and off. And the cost in time and money to troubleshoot and repair when it gets a few seasons on it.

In the big boat world with five or more ac systems controlling two or three pumps, lots of people turn the pumps on in the spring and leave them on until winter. I have five ac units switching two pumps and cannot recall when they were ever both off at the same time. There is always at least one unit in each bank that is running at any given moment calling for seawater cooling.

Given that you wil either be on genset or shore power anyway, how much will you save?
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Old 08-24-2019, 12:36 PM   #9
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Quote:
Originally Posted by O C Diver View Post
Not sure why a water pump would be optional, it's either air cooled or water cooled.
I suspect that it is to give you the option of using an old already installed pump or to share one pump between more than one unit ? Of course, it also makes the price seem lower until you add in the pump :-)



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Old 08-24-2019, 03:13 PM   #10
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Woodland Hills,

Another consideration is that pumps are more at risk for for sucking something in when running. So, especially in Florida, if moored or docked in shallow water, I don't want mine running except when it needs to be running. If it takes the duty cycle from 50% to 100%, that is twice as often I need to change filters or go snorkeling to clean things out.

Coming from California to Florida, where AC is used much more commonly and with a greater duty cycle, and in shallower waters, I was initially shocked by the number of boaters who had household units to cool and/or dehumidify boats at the slip and used their marine units only while underway. As I buyer, when I asked, I got the same reaction all of the time, "It is for cooling/dehumidifying at the slip. The marine unit does work, and is used underway, but the owner got tired of having to keep cleaning the intakes and strainers from the shallow water, debris, and growth near the slip."

I haven't done that on my boat, yet. But, I have had to take significant non-AC steps to control humidity and stay after the strainers frequently, even with infrequent use.

I'm glad mine turn on and off. If I had many units, I might consider fewer pumps and relays. But, with only two, I'm glad to keep the plumbing and switching system simple and have each one turn on and off its own pump. And, if any one goes down -- at least I have a cool respite in the other zone and, with a few fans, could keep the air circulating and humidity down, if that would ever become an issue again.
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