Originally Posted by Hoghead
That is what I am looking for - thanks
There are 3 pumps involved:
Ikiwa mag drive centrifugal aircon = 26 USG/Min
Ikiwa mag drive centrifugal feed to the HP watermaker pump = 4.2 USG/Min dicated by the feed pump output rate
pump = 3 USG/Min
The most likely high flow operating scenario is genset + aircon = 29 USG/Min
Or more commonly genset + watermaker = 7.2 and a non-issue
It is possible if the house batteries are fully charged and no load on the genset to run all three at 33.2 USG/Min
Will try and locate the strainer low and the 2 Ikiwa centrifugal pumps with a positive head on the feed
I also see that Groco has "high flow" fittings for 1.5 NPT that use a 1.75 hose and I am going to try this. Groco through hulls are high flow.
How much flow could a 1.75" ID hose support?
The 1.75" hose may help, But it's tough to say without seeing the layout. The issue is pressure drop on the suction side of the pumps. As in there is not lots.
Assuming you have a foot or two of positive head at the through hole. That at 35 gpm will be taken up with entrance loss and pressure drop across the strainer before we even get into pipe, hose and valve pressure drop.. Then your into NPSH (net positive suction head) which is the part between 0 psig "gauge" and 0 psia (absolute) which is 14.7 psi or 33.9 ish feet absolute head at sea level.
I tried to google
the ikiwa pump but got no where. So I looked at a march pump, series 6 for 26 gpm. It needs 15 feet npsh to function at 26 gpm. That leave all of 19 feet to use as suction pressure drop, which factoring valves and fittings should be enough. Worst case the pump cavitates, which will reduce flow, make noise
and generally cause an early death to the pump. Placing the pump as close as possible to the manifold will help prevent that.
Also placing a check valve on the outlet of the AC pump would be recommended. If the genny was running and AC was off, it might be possible for the genny raw water pump
to pull air back through the AC pump. More so as the strainer filled with "stuff". That would cause the generator
to run hot. A check valve in the discharge after the AC pump would prevent that. Please note that check valves in seawater tend to fail at some time. So it's something that would need checking and R&Ring every so often.
Both the genny and the HP pump on the water maker will be positive displacement so air would not be drawn backwards through them. Only the AC pump is the issue. My guess is the 1-1/2" hose should be enough. As long as you don't have a long run of hose before the AC pump.