While I try to make most of my blog posts somewhat generic and appealing to most, this one ain't that. This post is about a very specific electrical defect that I frequently run across, and I'm writing this post so I can give my clients a better explanantion of this defect. Oh, and also so I can give my clients proof that this isn't some new requirement that I just heard about.
The problem I'm addressing today is double tapped neutral lugs in electric panels. A 'double tapped neutral' is another way of saying that one of the screws on the neutral bus bar in the panelboard has more than one neutral wire feeding to it. This is a no-no, and has been for very long time.
One reason that two neutral wires can't be connected to a single terminal in a panelboard is so that the circuit can be isolated if it needs to be worked on. There is a great explanation of this at the Schneider-Electric web site. The other reason you can't have two neutral wires connected under a single lug is because the connections might come loose. While panel manufacturers will allow for up to three grounding conductors under a single lug, they typically only allow one neutral wire. The grounding conductors aren't going to normally carry current for extended periods of time, so they have a very slim possibility of coming loose. This isn't the case with the neutral conductors.
Despite what many seem to think, this didn't become a new requirement in 2002. This has been a requirement of UL 67 for a long time, but was spelled out in the NEC in 2002. Oh, and for the record, if a home inspector recommends a repair of say, a double tapped neutral, they're doing it for the reasons listed above; not because it's "code".
Reuben Saltzman, Structure Tech Home Inspections - Email- Home Inspections in Minnesota
