Originally Posted by BobandJoann
We are replacing our marine a/c water pump which is 320gph. We are looking at a pump that is 300gph & a pump that is 500gph. We do not know if the pump we are replacing is the original one. Our question is should we go with the 300 or 500?
All pump ratings are based on open discharge at rated voltage. The actual output will vary greatly depending on system head
loss (caused by flow resistance and lift
requirements), as well as actual voltage.
The original system was designed with these considerations in mind, and there was a good margin of safety
built in, to allow for these variations.
Depending on the system, the actual flow of the original may be only 150 GPH and the replacement 148 GPH (for example), depending also on the shape of the pump curves.
This variation may be equal to like a 0.25 Vac drop in supply voltage.
For all of these reasons, if the 320 GPH pump worked fine, I'm 99% sure the 300 GPH pump will as well.
Disclosure: I sell and install Marine Air Conditioning
systems. The post is offered as free advice and is not intended to solicit business.
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