Do you need a Balancing Valve on a pump with a VFD

[BronYrAur]

I am questioning the need for a triple-duty valve on a pump with VFD control. Actually, I'm questioning only the balancing part of the triple-duty. Pumps always seem to be specified with triple-duty valves as standard trim, but are they necessary with VFD control? It seems to me that isolation and checks valves are all that should be needed. the balancing part just adds more pressure drop. As long as your coils balance out correctly, do we really have to balance the pump? I suppose it may take longer to get the full-load design balance by just adjusting the VFD, but ultimately it will result in a lower frequency setting and save energy.

 

[RossABQ]

I've been thru this with many clients, many of whom have old specs (pre-VFD). Now most of them are comfortable without them on VFD-driven systems. It's a total waste of energy, if you have identical pumps on a reasonably "balanced" piping manifold.

Circuit-setters at the coils are still a good idea.