Air Handler Coil Booster Pump Sizing

[BronYrAur]

I need some assistance on how to size a booster pump for an air handler coil. I have a large chilled water system serving multiple air handlers, so essentially I have a bunch of parallel loads in the hydronic circuit. One air handler isn't getting enough flow, so the suggested correction is to put a booster pump in the branch feeding that unit.

Attached is an oversimplified sketch. I have concerns that this new booster pump may affect flow in other circuits. I don't know if there are check valves. But my question for the forum is how do I determine the required head of the booster pump? This pump will now be in series with the system pump, however not directly in series because there are multiple other branches. I assume the booster pump needs to be sized for the flow of the coil, but how do I go about calculating the head? I know the path of flow is the entire circuit through the coil, back through the chiller (not shown) and system pump. However, much of that head loss is accounted for by the system pump.

I have always had trouble finding good information on having different pumps in series, but this is even more difficult because of all the other branches in between.

Any help would be appreciated.

 

[bimr]

The manufacturer of the coil should be able to provide you with the head losses across the coil.

 

[LittleInch]

Assuming your main pump is good enough to handle the combined flow, it means that one of the otherAHUs is getting more. A simpler remedy is to add some control valves, manual or auto, to reduce flow in the AHU, probably the first one nearest the pump.

Adding pumps will just complicate things. The head loss will be low but flow relatively high.

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