Variable flow primary pumping, min flow bypass valve sizing question

[Waramanga]

Hi guys,

How does this valve get sized?? My approach would be to size it based on the size of the largest boiler/chiller pump. Do you still need to do an authority calc on it ie a 250kpa pump would need a fully open dp of around 65kpa when flowing the largest chiller/boilers water flow. Even though the valve always have the full pump head accross it, does the authority calc tell me anything about the valves ability to control the flow in the bypass??

thanks

 

[Drazen]

you should tell more about whole hydronic system, it is important to know flow variation pattern.

 

[SAK9]

With variable primary flow systems the minimum bypass line is sized for the minimum safeflow of the largest chiller.It would generally be operating when the load flow is low so the pump operating head across will be less than design head.Valve selection should be done based on an authority calculation based on likely operating conditions for maximum accuracy.

 

[urgross]

The valve would need to handle range of flow from minimum flow of smallest chiller to minimum flow of largest combination of chillers to be used (unless running in series).