Which Air Conditioner Pump?

J

JVM225

Active member
Member
Joined
Aug 20, 2007
RO Number
28365
Messages
2,332
I have the original 10,000 BTU Cruisair reverse cycle A/C - Heat on my boat.
It's time to replace the water pump. It has a small leak, and needed a tap to get it to spin.
Other than that, the unit works fine.
I can't make out the numbers on the original pump (it's kind of old).
After googling replacements it looks like I am going to be ordering a March Pump.
My question is: Do I need a 250 GPH, or 500 GPH.
Does anyone know?
Thanks in advance.
 
Get the biggest pump at will match your hoses...
 
+1 The biggest pump that will fit. The more water you pump, the more efficient your A/C will be.
 
I installed a March pump rated for 24,000 BTU's for my 18,000 BTU's that I have on my boat. It was still 70 GPH less than the Cal pump it replaced. I am still having to deal with the lower flow rate and unsuccessful-kicking myself now that I did not get the next step up pump. +1 on going with the larger pump-very rare to have too high a flow rate that affects the A/C operation in a negative manner. Just my 2 cents.
 
A 250gph pump is good for up to 8,000 btu's and a 500gph pump is made for up to a 16,000 btu unit. Those are the recommendations of Marine Airrrr.
 
quote:
Originally posted by capt6650

+1 The biggest pump that will fit. The more water you pump, the more efficient your A/C will be.

Click to expand...


Not true. You can pump through to much water and actually reduce the efficiently of your unit. Plus you could be wasting money by buying a pump larger than you need.

But in this case I'd use the 500.
 
Yes, biggest is not better. CruiseAir can tell you what size pump is just right.
 
Just called Dometic/Cruisair Tech Support.
He recommended that I try to determine what size is in there now, and replace it with the exact same size.
Told me that if it's a 250 and I install a 500, especially on an older unit, I risk rupturing the condenser and flooding the compressor.
Not knowing too much about Air Conditioning systems, I think I have to go with what he tells me.
He also told me that March has made the pumps for Cruisair for many years, and that the pump I have is a March pump even though it has a Cruisair label.
I was hoping to be able to get the new one, and just swap it out. But now it looks like I'll have to pull the old one out first, see what I have, and then try to order a new one.
 
I agree that upsizing the pump doesn't provide any benefit if you have to use adapters to get the hose size down to fit the system. But if both pumps use, say 1/2" hoses, you have nothing to loose by using the bigger one, pressure isn't going to go up and you are Not going to damage the coils

Boat builders and AC installers install the pumps, not cruisair. . There is no guaranty the pump was sized correctly or that the hoses were routed properly.. The longer the run, the less flow. I could also have been replaced since 1987.. Chances are it was anyway. How many times do we hear that people have pumps that don't self prime as they should because some builder didnt bother follow simple install instructions...
 
Thanks to all for the input and advice.!

I got back in there with a better light and stronger reading glasses and found the model number of the old pump on a portion of the label that was curling up. These 59 year old eyes need all the help they can get.
It's a 250 GPH model.
Called Cruisair back and they told me that the 250 is sufficient, and more than likely what was initially installed because they used that size pump with units up to 16,000 btu depending on the application. Mine is 10,000 btu. Sounded like the shorter runs got the smaller pumps, and the longer ones got the stronger ones.
The tech I spoke with had an installation service business on the Gulf Coast before going to work for them, so he sounded pretty knowledgeable.
I asked him the downside to going with the 500, and like the tech I spoke with earlier, he cautioned that on an older unit you could possibly rupture the condenser. May not happen, but it could cause it to prematurely fail.
Called March back and they confirmed that the 250 GPH model is sufficient to run my unit.
The 500 GPH pump has larger diameter inlet and outlet on it anyway, and I would have to somehow reduce them to accommodate my hoses. Which would probably negate a portion of the benefit of the stronger pump. Or, have to go through the hassle of changing the hoses (and possibly adapting the strainer)which are in good shape.
To avoid possibly opening up a can of worms, I ordered the 250 GPH model.
My thought process is that it has done the job really well for the 7 summers I've owned the boat, and although the larger pump may (or may not) work a bit better, why mess with it. I don't feel like I know enough about the AC system to start making modifications like that anyway.
Thanks again for all the great input.
 
You must log in or register to reply here.
Back
Top