Overload Protection

[rjgollogly]

I have multiple 120/208 3-phase circuits feeding from an Uniterruptible Power Supply (UPS) going to a control panel in another room that houses a contactor for each seperate 120/208 circuit. These contactors allow us to turn power on/off to each seperate part of the trainer individually. Two of the circuits are for cabinet power (rack full of computers and such plugged into a pulizzi power strip which has its own circuit breaker protection). Another one of the circuits feeds a seperate sub panel for trainer power that incorporates its own circuit breaker protection.

My question is per code do I need to have overload protection for these circuits in the control panel? They have overload protection in the UPS. They come into the control panel for power turn on/off capability and leave and are overload protected at the destination. Thank you and have a good day.

 

[augie47]

Does your UPS have properly sized overcurrent protection for each of the separate feeders leaving it or does it simply have overall overload protection ?
The feeders would need to be protected according to their ampacity unless they meet one of the 240.21 tap rules.

 

[rjgollogly]

The UPS does have properly sized overload protection for each separate feeder leaving it.

 

[augie47]

That would be fine except in re-reading, I may have worded my question incorrectly. The power going to a subpanel would be a feeder. The other power going to the contactors seems to be a MWBC as it has no downstream OCP. From an overcurrent standpoint you would be o.k. as your UPS has OCP. If you are under the '08 Code you would need to be sure that OCP complies with 210.4(B) in having a means to simultaneously disconnect all ungrounded conductors.

 

[rjgollogly]

Augie, what does MWBC stand for? The power going to the contactors does have OCP when it gets to the destination. Each contactor only feeds one cabinet. When the power comes into the cabinet it lands on a pulizzi outlets strip that has its own 3-phase overload protection.

 

[augie47]

That's why I gave you a Code reference...
MWBC=Multi-wire branch circuit
It's probably going to be a judgement call by an AHJ.
210.4 is for "Branch Circuits" and IMHO, it will depend on how the OL protection after the contactors is classified. To me it sounds more like they would be "supplemental overcurrent protection" and 210.4 would apply to the OCP at your UPS prior to the contactors.
What amperage is that OCP (at the UPS) ?

 

[rjgollogly]

There is a 200A main circuit breaker on the UPS that feeds the seperate 30A three phase breakers that my feeders come off.

 

[augie47]

As stated, as far as OL protection, I see no problem as long as your conductors have the ampacity of the breaker at the UPS, (in your case #10s.)
The "handle-tie" to me is a judgement call where, sight unseen, I lean toward requiring it.
(all depends on classifying the conductors to the contactor as "branch circuits".