Greetings,
A couple years ago we poured a pad for a generator and transfer switch. The transfer switch will be located on the outdoor pad next to the generator. Under the pad are 3 sets of 3" schedule 80 PVC (see picture before concrete was poured). 9 conduits come up at the transfer switch, 3 of these go to the generator, 3 to the service, and 3 to the transformer.
A couple years ago this was going to be 800 amps but today it is 1200 amps (500 KW generator instead of a 300 KW). Using compact conductors I can almost use 600 MCM copper. I would have a 3/0 equipment ground and as small a neutral as possible to squeeze it into the pipe. I haven't done a neutral unbalance calculation yet.
Does anyone know of a compact conductor that maybe has a little smaller dimension than is listed in Chapter 9 Table 5A? Because the generator, transformer, and 1200 amp service are all within 10 feet maybe the inspector will allow a little fudge. Three 500 MCM calculates to 1140 amps and I don't think I can go to the next size breaker as it is over 800 amps. I'm probably ok coming from the transformer as this can be 4 wire rather than 5 wire. Now I wish I had used schedule 40 as that would give me some more room. Any ideas or help would be appreciated. A saw, hammerdrill and a 4th pipe covered with 2" of concrete is not completely out of the question but would be an enormous amount of work. Thanks!!
Dave K
A couple years ago we poured a pad for a generator and transfer switch. The transfer switch will be located on the outdoor pad next to the generator. Under the pad are 3 sets of 3" schedule 80 PVC (see picture before concrete was poured). 9 conduits come up at the transfer switch, 3 of these go to the generator, 3 to the service, and 3 to the transformer.
A couple years ago this was going to be 800 amps but today it is 1200 amps (500 KW generator instead of a 300 KW). Using compact conductors I can almost use 600 MCM copper. I would have a 3/0 equipment ground and as small a neutral as possible to squeeze it into the pipe. I haven't done a neutral unbalance calculation yet.
Does anyone know of a compact conductor that maybe has a little smaller dimension than is listed in Chapter 9 Table 5A? Because the generator, transformer, and 1200 amp service are all within 10 feet maybe the inspector will allow a little fudge. Three 500 MCM calculates to 1140 amps and I don't think I can go to the next size breaker as it is over 800 amps. I'm probably ok coming from the transformer as this can be 4 wire rather than 5 wire. Now I wish I had used schedule 40 as that would give me some more room. Any ideas or help would be appreciated. A saw, hammerdrill and a 4th pipe covered with 2" of concrete is not completely out of the question but would be an enormous amount of work. Thanks!!
Dave K
