Tom Jenkins
Lifetime Supporting Member
A couple of thoughts:
Running identical pumps at the same speed produces the same flow in an ideal world, but not necessarily in the real one. You should probably also monitor power or flow to provide early warning of problems like impeller wear or pipe blockage.
There is a minimum speed for centrifugal pumps, below which the pump won't produce enough head to move any water. That should be set at your VFD or controller.
I don't like continuing to run one pump at 100% after bringing on the lag. When you bring on the lag you will go from 100% capacity to 130% or so - a jump that may disturb the system. I prefer to ramp down the lead to 50% and bring on the lag at 50% for a bumpless transition. Then whether you ramp one or both is a matter of personal preference.
Running identical pumps at the same speed produces the same flow in an ideal world, but not necessarily in the real one. You should probably also monitor power or flow to provide early warning of problems like impeller wear or pipe blockage.
There is a minimum speed for centrifugal pumps, below which the pump won't produce enough head to move any water. That should be set at your VFD or controller.
I don't like continuing to run one pump at 100% after bringing on the lag. When you bring on the lag you will go from 100% capacity to 130% or so - a jump that may disturb the system. I prefer to ramp down the lead to 50% and bring on the lag at 50% for a bumpless transition. Then whether you ramp one or both is a matter of personal preference.