Pump upgrade (Houston): 2-spd versus VS recommendations

[mas985]

0.635 meters of vacuum is 25 in hg. which is very close to cavitation which is why they specify that. There is very little chance that you will have that much vacuum but if it is a concern, you can purchase a vacuum gauge and measure the vacuum at the pump.

Exactly how did you calculate your head loss? Your numbers do not make sense. An Intelliflo will never reach run out on a typical setup so 160 GPM is not possible.

 

[Bama Rambler]

.635 meters (635 mm) of vacuum = 25" of Hg vacuum. That's a tremendous amount of suction head (~28.3').

Mark beat me to it, but i'm posting it anyway because I did the math. :lol:

 

[PandT]

Mark,

I used fitting loss values and friction loss calculator on Lasco website. 2" PVC (Schedule 40), estimated horizontal and vertical pipe lengths, number of elbows and tees (mostly not straight thru), and included 6.0psi drop thru DE filter (perhaps should exclude since it is downstream of pump outlet). Came to 80 eq feet without DE filter.

Thanks,
Patrick

 

[mas985]

80 equivalent feet is much too low for a typical plumbing setup so something is not quite right with the way you did the calculation. Note too that the head loss in the filter is proportional to the square of the flow rate and is not a fixed number. This is true of all the plumbing so it needs to be solved as the intersection of the plumbing curve with the pump curve.

A typical 2" plumbing setup will have a plumbing curve close to:

Head loss (ft) = 0.0082 * GPM^2

This has the equivalent pipe length of about 543' of 2" pipe.

This results in the following operating points:

3450 RPM, 101 GPM, 84' of head
1000 RPM, 29 GPM, 7' of head