Find out the max. length of the decoupled bypass in primary/secondary 1

[henryt1]

Hi anyone,
We have 12" common pipes for the primary/secondary chilled water system. Due to the space limitation of the pump room, the contractor reroute the 12" decoupled bypass pipe to 7 ft. On center. Does anyone know how to figure out the maximum length or by rule of thumb for the decoupled by pass pipe? thanks in advance

 

[KiwiMace]

If your bypass is the same size as your headers, then you are probably going to be in good shape.

Your worst case flow scenario is a second chiller starting up when the secondary is not at full speed. This flow rate, nominally assumed around 125% of the chiller flow, will be in your bypass. You want to keep the bypass dp negligible wrt your primary and secondary loops so that the chiller start will not unbalance the secondary loop - thus 'decoupled'.

 

[henryt1]

Thanks KiwiMace