I'm under the impression that for proper generator hook-up, the grounded conductor must be opened along with the hot conductors to completely separate the main system from the emergency circuits...I've yet to find anything in the NEC that supports this; the part about separately derived systems and Emergency Systems (Article 700) is a little ambiguous when it comes to the residential situations. My neighbor- a retired Master mining electrician- is happy to have his generator hooked up to a double pole breaker in the panel, where he kills the main and backfeeds the buss with the generator. I personally don't like that. I've got mine set up this way...
> A 50A 2 Pole breaker feeds a 50A Four-wire Receptacle. A #6-3 w/#8G Cord and plug feeds the Emergency Panel. Another four-wire 50A receptacle is fed by a #10-4 SOW cord that connects to the generator, protected by the generator's circuit breaker. One simply plugs into the appropriate receptacle for either main or emergency power...nice and safe...Right? (Cheap too...) But I'm suspicious that there are still codes being violated by either means... Can one feed a 50A receptacle with a 20A Breaker by code? I can't find it... but some thing tells me "no".

At any rate... pardon my ignorance in this topic. I've seen pictures of residential transfer switches that appear to be two 2-pole mains connected with a bar to make them essentially one unit with only one pair being closed at any time. (Seems to me that under the right short-circuit conditions...say a shorted buss with both main and generator power available... said breaker(s) would oscillate between the two positions and never really protect the circuit... first opening one breaker which closes the other ad infinitum... )I have to assume that this is safe and legal and that I'm just missing something somewhere...

Any comments?


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI