Taps for panel lighting disconnects


Thread Starter

Rich Waskowitz

I am aware of and have read the pertinent sections of NFPA 79 regarding taps (8.4)and main disconnect mounting (7.8.1). My question is, How does one take a tap from the line side of a 400 amp CB main panel disconnect to supply a 1 KVA lighting disconnect/transformer? You can't just jamb a number 10 in with the 600 MCM feeders. You can't put a distribution block above the main breaker and tap off there. The lug supplied with the breaker sure doesn't have an opening for 600 MCM and one for #10. I know this is being done all over the place. How are you doing this?

Also, if the light box tap conductors terminate at a little 16 amp rotary disconnect switch inside the lighting disconnect, does that mean I cannot use exception #2 of 8.4 since it lists only "a splitter block, circuit breaker or a set of fuses" but not a rotary disconnect. If so, then how do I get the #2 AWG required to meet the 1/3 rule down to a manageable size?

No, I failed to mention that this is in an industrial setting that falls under the NFPA requrirments.

Rich Waskowitz

Sorry, I guess I think faster than I type....
What I meant to say was that this panel is part of an industrial machinery installation that falls under NFPA 79. The NEC ends at the "place of connection of the supply to the elecrical equipment of the machine" (NFPA 79 1.1.1)
You may use a grounded 120V machine control circuit with seperate overcurrent protection for the lightning circuit. Just use yellow wires since
the disconnect will not disconnect the power source on this supply. i.e. You do not have to use the main feeders.

Bob Peterson

Look closely at your line lugs. Most of them have a small tapped hole in them just for this purpose. You can just use a ring tongue terminal for your control power connection and a machine screw to connect the terminal to the lug.

Bob Peterson
Thanks, I found out about these too. Sd-D does offer as an optional lug, one with a 6-32 tapped hole which may work in some cases. However, I have also found that Ilsco makes a line of tap connectors with snap on insulation covers that clamp over that larger conductor and have set-screw terminals for smaller taps. I will probably use these.