I have a customer that has dozens of 3-phase, 4-wire switchboards operating at 400/230V. Yes, it is a unique facility. The switchboards are UL 891 listed and have power quality meters mounted to hinged panel covers on the front of the gear. The meter's voltage sensing does not use PT's so 230V-to-ground terminates directly to the meter V1, V2 and V3 terminals. The meter is rated for over 500V-to-ground so that is not a concern. I'm just wondering if there is a limit to what voltage can be directly connected to the interior side of a hinged access panel on the front of the gear. I've been told the limit is 250V but I can't find that in any standards. That would explain why some meters have remote displays mounted on the front keeping the high potential wiring inside the cabinet. These particular switchboards are located in controlled electrical rooms so only qualified personnel would have access. Any thoughts would be appreciated.
Voltage Sensing Wiring to a Switchboard Mounted Power Quality Meter
- Thread starter bsoucy
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Would be covered by the UL product standard. Not a nec issue.
As far as I know there is no such rule. However, you may get some dispensation for keeping the voltage on the door under 30 volts or some such number. Like no bonding required.
As far as I know there is no such rule. However, you may get some dispensation for keeping the voltage on the door under 30 volts or some such number. Like no bonding required.
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