Pump Location

J Van Lund

1) I have a small in-floor hydronic heating system (1500 sf) which has a Grundfos UP15-42SF circulator, which meets the system's circulating needs. We can mount it in a horizontal or vertical run of pipe. Will it perform better in the vertical run of pipe or the horizontal?

2) We read there should be a straight run of pipe equal to ten pipe diameters between the pump inlet and a 90 degree bend to avoid cavitation problems. So for a 3/4-inch diameter inlet pipe, there should be at least 8 inches of straight pipe before the 90 degree bend. Do you agree?

3) Should the same rule apply to the outlet side of the pump?

4) In a closed or dedicated system, does it matter if you pump toward the expansion tank or away from it? Everything we have read indicated that Rule #1 in hydronic heating is to always pump away from both the expansion tank and air separator. Do you concur?

Thanks for your help.

Alan(CaliforniaRadiant)Forbes

Some answers

1) Vertical or horizontal makes no difference, just make sure the shaft of the motor is horizontal.

2) Yes, I agree.

3) No; there aren't so many rules for the discharge side of the circulator.

4) Yes, pump away from the x-tank which is usually (but not always) attached to the air separator.



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