Primary pumping should be with vfd or constat speed

[vi007]

In our project we have 4 hot water heating boilers. 3 working and one standby.There are 3 primary pumps with VFD, 2 working one stand by and also seccondary pumps with VFD which serve different loops of Air handling units, H & v UNITS, CONVECTORS ETC. If there is a demand during winter the secondary loop serves the purpose. Now the question here is do we need primary pumps with VFD or we can run primary pums at constant speed as secondary loop with VFD is already taking care of fluctuation. Let me know if you need any other info.

 

[quark]

Better to run the primary pumps at fixed flowrate and sequence the boiler operation as per secondary load requirement. Unlike chillers, boilers give you good efficiency even at low deltaT conditions, so variable primary is not hard and fast. Moreover, you are keeping the coils safe.