Pumping Question

Chuck_7

I have a project where we are adding capacity to an existing water source heat pump loop.
We are adding almost 50% to typical water source heat pump loop that has two existing basemounted pumps (one is a backup).
The new water flow requirement can be just barely met by one of the existing pumps with no room to spare based on a calculation.
Choose from the following:
1. Use the one pump and hope the calculations are accurate enough.
2. Use both existing pumps (backed up the curve) so each pump handles 50% of the total flow. No back-up.
3. Add a third pump in parallel so two pumps are use (where we want to be on the pump curve).

Opinions?

Jamie Hall

were it I...

I'd go with option 3; get a third pump as a backup. And if at all possible, wire the controls so that all three pumps got run on a regular basis...

Vince Gorichan

I would

look very carefully at the curves and actual impeller size on the existing pumps. If you have enough horsepower left, you can sometimes put in a larger impeller to increase the capacity. You can check HP via an amp reading to confirm the pump curve prediction. If one pump is still short, do parallel pumping. This will probably yield about 20-25% more flow.
Your local pump rep. will probably be glad to assist w/ the analysis. Last resort, three pumps. Is the system constant flow? How about a variable flow refit while you are at it. Do not fret the GPM total. Most HP systems can function over a range of flow. Do you need all of the GPM? Check it out.