Double Tap Questions

Hello gurus and mini-gurus. I would like specifics on “allowable” double-tapping. If the breaker is Square D, CH, or other approved by the manufacturer for double tap, I think the gauge must still be the same for each conductor AND each conductor must be in its own slot, that is, one on each side of the screw, is this right?

In a case of double tapping not permitted, is it a permissable repair to join the two conductors to a short pigtail with a wire nut in the service panel, so that the pigtail goes to the breaker? If that is OK, provided the total load is still acceptable for the breaker size, double taps are not that serious of a defect in terms of repair, right? :neutral:

Section 110.3(B) requires that all equipment be installed and used in the same manner in which it was listed and tested, following all instructions that accompany or are available for the product. Section 110.14(A) requires that terminals suitable for more than on conductor be so identified.
UL and practical experiences throughout the country indicate that the terminal may not remain tight (resulting in overheating at that connection) when more than one conductor of any size is used, unless that terminal is specifically tested and listed for use with more than one conductor. Information on whether two wires can be installed at one breaker is marked on the product (molded into or printed on circuit breakers), on the disconnect labels, in the instruction manuals for load centers, in the catalogs for some of the products, and on the cut sheets for other products.
Wiring something that was never tested for that type of installation, not approved by the manufacture and not allowed in the NEC is a serious thing.

Yes, they should be the same size conductor. CH doesn’t have individual “slots” but Square D does.

Yes, you can splice two circuits to one conductor to eliminate the “double tap.”

On the double tap question, can you double tap a fuse as in this picture?
This also seems to be a fused neutral, is this what they would typically look like were I to find more?


I don’t see a fused neutral. The two conductors coming in from the top are fused. There’s no way to determine if one of those is a neutral, but I’m assuming they’re both hot.

The white and black conductors (that come up from the bottom and attach to the terminals above the fuses) are what I call a “direct tap” - meaning, they have no overcurrent protection. You could open the switch and remove the fuses, and those conductors would remain hot.

Yeah, Matt. Whatever you “violation” you pick, pick something to call this out. It’s been wrenched on over the years, and needs a little attention from an electrician. If nothing else, call out the fact that an open knife switch presents a life/safety issue to the occupant if they ever have the need to operate the disconnect.

Does anyone ever call out the fact that some of these boxes are old and should just plain be replaced? These things were not made to last forever. After all, our country survives on built in obselence. At what point do we call for replacement.

That might not be too pallatable to a comsumer, but there’s surely something hazardous about an old installation that you can point out. The open kife switch in this thread is a good example.