fresh water pump and pressure


Mark Pitt
 

I am considering replacing the fresh water pump, accumulator tank,
and pressure switch on my ASM with one of the new variable speed pumps
from Jabsco that do not require a separate accumulator tank or
pressure switch. My current pump is the big 40 liter per minute (10.6
gallons per minute)AMFA A88B that delivers up to 29 psi (2.0 bars).
This is the optional pump intended to supply plenty of water to the
optional hose outlet under the helm seat. The pump and the pressure
switch have been giving me problems.

Jabsco has a new 29 liter per minute (7.5 gallons per minute)
variable speed pump,the Jabsco 7.5 VSD (part 41755-0094 for the 24 v
model) that probably delivers enough water for my needs as I almost
never use the hose outlet. It self-primes to 1.8 meters versus 5.5
meters for the AMFA A88B (and the ASM standard A66B), and can run dry.
It's pressure shut-off is 50 psi, which is significantly higher than
the 29 psi of the AMFA.

Has anyone had any experience with a variable speed pump before in
an Amel or any other vessel? Is the higher cutout pressure of 50 psi
a problem? It seems that 40 psi is quite common on smaller, switched
pumps. Shurflo has a variable speed pump, the Extreme Smart Sensor
5.7 that delivers 21.6 liters per minute with a shut-off pressure of
65 psi. I do not know why variable speed pumps have a higher shut-off
pressure or whether this is a concern in an ASM. Any enlightenment
would be appreciated.

The specs of the AMFA pumps are found at
http://www.reya.com/English/framespumps.htm
and the Jabsco at
http://www.jabsco.com/files/marine_product_guide_2006.pdf.

Mark Pitt
Sabbatical III ASM #419

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