Relay panel

[joeyww12000]

As you know a relay panel doesnt have a neutral bar.....You only pull in your line side conductor from your feeder panel and your load side conductor going to the field for whatever your relay is controlling, your neutrals/grounded conductors and grounds go to the feeder panel.......... In a relay panel with several relays you can have alot of conductors intering a panel with no neutrals/grounded conductors......does this cause any inductive heating? Is there a code for this in relation to relay panels and such?

 

[don_resqcapt19]

There is no issue as long as the supply and the switch leg are in the same raceway. The current will be going in opposite directions and it will not cause any problems.

 

[acrwc10]

The way they conductors are routed could cause an issue, like Don said you need to have the current that opposes the circuit with the switch leg to cancel out the induction. If you have your feeds coming from one direction and the switch legs coming another in different conduits it could be an issue.

 

[S'mise]

As you know a relay panel doesnt have a neutral bar....." ".....does this cause any inductive heating? Is there a code for this in relation to relay panels and such?"

Some do have a neutral bar. It's a grounded secondary on the control transformer. I have seen 3 wire mid-tap neutrals on control panels, but most are 2 wire 120v control power(not technically a neutral) but it has a ground bar or terminal strip complete with white (grounded) wires going to it.

Yes, inductive heating could be a problem if routed poorly but it's rare. Relay/signaling circuits are usually very low power and the panel wiring is usually larger than needed.(#16 in panel with #14 in field)

NEC discusses Industrial control panels, But relating to machinery controls refer to NFPA79

 

[infinity]

To avoid potential induction issues you could run the neutrals through the relay panel and on to the load. Here's an example of a relay panel without a neutral bar and the neutrals run through it to the load conduits: