Hot Water Pump Sizing 1

[swoosh172]

I am sizing hot water circulating pumps for a 3 story building for a vav w/ reheat system. My question is do I take into account the static head required to pump to the highest hw coil in a VAV box on the 3rd story (pumps in the basement), or do I just take into account the pipe friction losses as the contractor will precharge the pipe to adequate pressure during installation?

 

[kbs]

Friction losses only as it should be a closed loop. You are circulating the water not lifting it.

 

[EnergyProfessional]

the contractor doesn't really pre-charge the water. All pressure the contractor needs to fill is the gravity pressure, which isn't much at 3 stories. since water is not compressible, it is not really under pressure, like air would be, or refrigerant.

be sure you get the coil manufacturers pressure drop for the flow rate you need, same for valves etc.

It doesn't sound like you use a software (I have Trane Pipe Designer and that works fine). Here is a free tool

http://www.taylor-engineering.com/publications/design_guides.shtml

(the cool tools pipe optimization)

 

[ChasBean1]

kbs is right; as low as about 20 psig city water pressure should fill it; the circulator in a closed loop only has to overcome friction losses.