We had a brief discussion in my alternating current principles class last night. The instructor was convinced that all grounded conductors at a receptacle location had to be pigtailed in order to not break the grounded path. Obviously, that's the best way to do the wiring at the receptacles, but is it necessary by the NEC? I only see this rule applying to multiwire installations where breaking the neutral could do serious damage to an appliance (like a PLASMA TELEVISION) if ever broken.
hey shock, how would you do it without a pigtail? put "two" wires under one recepticle ground screw? if so; where is the ul listing for this type of device? we all agree that the ground is the most important conductor and a pig tail would be the only way.
opps "ed" not "ing" my mistake.... then i agree, no pigtail required by nec. not sure about damage to equipment since the "grounding" would still be there. on a multiwire you open neut at homerun and you put 240 across the circuits and this is never good. although power tools run really fast for a little while yuk yuk.
The reason a device-dependent neutral path matters on multi-wire circuits is that, when handle-tied breakers are not used, one circuit can be deenergized to be worked on, but another sharing the same neutral can still be hot, making the load side of an opened neutral connection hot.
Larry, and isn't it true that if the grounded splice comes apart, one leg of the multiwire branch circuit will carry a higher voltage than the other ungrounded conductor? I seem to recall seeing/ reading this in one of my trade books somewhere. Could you explain why this happens?
At the risk of insulting everyone's intelligence on this forum I explain it this way- If you have a multi-wire branch circuit consisting of two ungrounded conductors and one grounded conductor, the loads of each of the ungrounded conductors are using the single grounded conductor for a return to the transformer. Should the grounded conductor be interrupted and the is no return to the transformer via the grounded conductor then the return path is through the other ungrounded conductor and any load on that other ungrounded conductor path, This could and probably would create a problem if the total current flow exceeded the limit of one of the components in this new found path back to the transformer. Example a 10a. load on one ungrounded conductor and a 1a. load on the other conductor now become a total load of 11a. and the 1a. load (100w. bulb for instance) would not tolerate the flow of 11a. and the bulb would burn out.