Voltage barriers

[jmbelectrical]

Upon reviewing some drawings by other engineers, I noticed that they specify the use of voltage barriers in lighting control relay panels when they contain lighting branch circuit conductors from both 480/277V and 208/120V systems. I know that the NEC requires the use of barriers in device outlet boxes when the voltage between branch circuit conductors exceeds 300V, however, to the best of my knowledge, this requirement does not pertain to boxes and enclosures. Or does it?

And if it does, how would one even provide a barrier in a lighting control relay panel? These panels can contain anywhere from 12 to 48 relays.

Thanks in advance for any input provided.

 

[waross]

Double voltage relays are typically designed so that one voltage is on one side of the barrier and the other voltage is on the other side.
One implementation used knock outs in the barrier and the lighting relays were mounted by being inserted into the knock out holes.
There were some double voltage relays on the market where the relay was mounted in an enclosure. The barrier was fitted around the relay so that the coil was on one side of the barrier and the contacts were on the other side of the barrier.

Bill
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"Why not the best?"
Jimmy Carter

 

[jmbelectrical]

It appears that I may have answered my own question. Cooper-Greengate's line of lighting control panels offer an option for voltage barriers, as can be seen in the following specification sheet: [URL unfurl="true"]http://www.cooperindustries.com/content/dam/public/lighting/controls/products/documents/greengate/spec_sheets/lk16_32_spec_sheet.pdf[/url]. I also found this piece of information from one of Cooper's other websites: "If normal and emergency circuits are present in the same lighting control panel, they should be separated by a high voltage barrier." I believe the rationale behind this is NEC 700.10 - Wiring, Emergency System.