One thermal/mag breaker with two softstarts

[justdavemamm]

In an industrial control panel (not part of an MCC) they have a 600amp thermal/mag breaker with door handle used for both OCP and disconnect.

Wired to the breaker is a power distribution block sized suitable (760A), then to two motor Soft Starters, each rated for 414 amps. The motors are 363 FLA.


Only one motor will run at any given time as this is for redundancy, they are connected to pumps that are piped in parallel. The control circuits are interlocked to ensure only one can run at a time.

Lacking is OCP from the power distribution block to the softstarts, the wire is only about 4 ft between them. The softstarts monitor incoming amps via CT's and can detect ground faults.


Is there a problem of not having OCP from the power distribution block to the softstarts ? Does each softstart need its own OCP ?

 

[augie47]

In ths area, if this is factory assembeld, the first thing we would do would be to look for the NRTL(UL) label then walk away. If you are wanting to diagose further then, although I may be overlooking something...(seems I have been on posts lately..old age, I guess) it appears the OCP is properly sized (for one) and since the starters are interlocked I see no problem.
You might check the soft start to see if the mfg has any restrictions concerning fuses vs breaker protection.

 

[justdavemamm]

augie47:

The softstart mfg lists both maximum CB and fuse size.

It is a custom control panel and not a factory (like GE or AB) assembled unit.

 

[augie47]

It just one ole farts (who happens to have a wall full of "certificates") opinion, but I see no probelm