AC pump size question

[Oldlaxer1]

I've been researching the AC raw water pump and have perhaps a stupid question. I read where you size the pump based on the # of tons (12,000 BTU) in your system. I have 4 individual units of differing sizes (24,000, 16,000 and 2 @ 10,000) all fed by one pump. (Oberdorfer 104M-06 rated at 1250 GPH). Typically we only have one or two AC units running at a time. Wouldn't that indicate too much flow or does the water flow through all 4 units even if only one is running? I'm trying to decide on a backup pump and the March pumps only seem to go to 1000 gph. Thanks in advance for any insight.
John

 

[Boatsb]

Does the one you have work?

If so replace with the same. Makes swapping it out easier and having a spare of the same type is always better than refitting it on a 100 degree day in a hot engine room.

 

[jim rosenthal]

The water flow has been through all units all the time when the pump is operating, on all the ACs I've ever had on boats (keeping in mind I've owned the same boat for 28 years!) I have never seen an arrangement where seawater flow through the coils was switched on and off depending on which AC unit was actually switched on at the time. All the seawater coils, all the time.

I agree with sticking with what you have. Oberdorfers are not cheap, but you get what you pay for. And on that size boat I'd carry a spare as well. Since all the AC units depend on the one pump.

 

[oceanjake]

How loud is the current pump? March pumps are pretty quiet, and the sealed koolair pumps are virtually silent. While it’s not scientific, I replaced a loud high volume centrifugal pump with a koolair with much lower output and have noticed no reduction in cooling even with 4 units running. Silence is an amazing sound.

 

[Oldlaxer1]

Does the one you have work?

If so replace with the same. Makes swapping it out easier and having a spare of the same type is always better than refitting it on a 100 degree day in a hot engine room.

Yes it is running. A bit noisy but running fine. I think I'll take your advice and get an identical one as a spare.
Thanks

 

[Oldlaxer1]

The water flow has been through all units all the time when the pump is operating, on all the ACs I've ever had on boats (keeping in mind I've owned the same boat for 28 years!) I have never seen an arrangement where seawater flow through the coils was switched on and off depending on which AC unit was actually switched on at the time. All the seawater coils, all the time.

I agree with sticking with what you have. Oberdorfers are not cheap, but you get what you pay for. And on that size boat I'd carry a spare as well. Since all the AC units depend on the one pump.

Thanks. I think I'll place the order now.