Metering appication: PT terminations in panels

mayanees

Senior Member
Location
Westminster, MD
Occupation
Electrical Engineer and Master Electrician
My question concerns the NEC requirements for tapping a circuit breaker output terminal for use in a metering application.
We're specifying metering throughout a facility where CTs will be installed at power panels.
If the panel has a spare breaker, it will be used for the voltage input to the meter. But in the case where there are no spares, we'll need to terminate the ~18 AWG tap wire for the meter on some voltage source. (it will be fused to comply with tap rules)
If the mains have 2/0 terminations, it would be easy to slip the ~18 AWG wire under the terminal and retighten, but I'm concerned that the terminal would have to be listed for that application.
Can anyone speak to that?
One alternative would be to intercept an output low-amperage feeder with a tap block and run the PT leads from there. But it would be so much easier to tap a CB output terminal.
Any comments or suggestions are appreciated.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
... but I'm concerned that the terminal would have to be listed for that application.
Yes, it would have to be listed for that application.

Most manufacturers offer some method for connecting these small control wires to their larger breakers. One style is a 1/4" tab that is built to fit under the breaker lug and its mounting pad. The most common method seems to be just a simple 'drill and tap' of the lug body itself to accommodate a small crimp-on style terminal.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
how would this approach be any better than just ignoring the listing and adding an extra wire to the lug?
Following my first statement; the method needs to be listed by the manufacturer.

Adding provisions for a dedicated small crimp style connector (e.g. a Stakon brand), fastened with a 6-32 screw, is certainly better than simply stuffing a small wire into a lug with a significantly different sized conductor.
 
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