Parallel VFD's

[arcadia]

Background;
I have two identical wells and mirrored VFD configurations.
Each well has the same 3hp Pentair Motor and a Pentair PID30 VFD.
Both VFD's have their pressure sensors located next to each other in the main line.
Both units are set to 30 Hz min and 60 Hz Max.
Both units set to 70 psi.
The units are connected together with a Pentair VFD-ALT operating in alternating lead / lag mode.
Both wells share one main line to the house and one pressure tank.

Problem:
The VFD-ALT has failed and I have to manually switch between the well periodically. New VFD-ALT shows available but is on backorder.

Notes:
Momentary testing of a few seconds did not produce any overpressure and both units seem to run at the same load.

Question:
Can I run both VFD's at the same time?

Thanks in advance!

Arcadia

 

[Valveman]

Sorry for the delay. Sorry for your problem. You really shouldn't run both pumps at the same time unless you stagger the pressure settings. Set at the same pressure one VFD will cause the other pump to deadhead an it won't last long. I never liked alternators anyway. You are technically wearing out your spare pump as fast as the primary pump. I prefer to stagger the settings and have one pump run 95% of the time. I use an exercise clock to make pump #2 run for 2 minutes a week only. That way it is still exercised, but will have much less use and be in good shape when a spare is needed.

Your biggest problem is the VFD's themselves, as they are made to give problems and be expensive. That is why all pump companies are pushing them. It is not because they are good for the consumer.