Service Disconnect Sizing

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360Youth

360Youth

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Newport, NC
I posted a question earlier about a job we have found ourselves in the middle of and I guess this is a part II. While working on generators for one job site, the foreman asked us to check out another. There we found a WWTP with an 800amp main, feeding a 400 amp ATS with no OCP, feeding an 800 MDP. Apparently there was a mixup in the specs the generator guy got and the ones the EC got. Anyway, the question now is whether or not it is legal to supply 400 amp equipment with no OCP other than 800 amp. I do not know what the calculated load is, but we were told the service was upsized for future expansion. 240.4 and 230.90 deal with sizing of OCP but is in reference to conductors, not equipment. 408.30 deals with equipment, but the article is Panelboards. I know it is done all day long when you have a 400, 600, ... amp services that the individual panels are 200 amp amp with 200 amp feders, but they also have the OCP built in. There is no such protection on this ATS, and that is where I think the violation is, but I do not have code reference to go back with. I want to be sure of myself because we are calling into question another ECs work and I like to tread lightly in such situations. What am I missing?
 
All day without a reply????

One way of looking at this is we now have conductors inserted into the circuit that are rated half that of the overcurrent device,
The conducting elements of the transfer switch are only rated at 400 amps and this matches a standard overcurrent device (240.6) therefore it must be protected at not more than its rating of 400 amps.
 
jwelectric said:
All day without a reply????

One way of looking at this is we now have conductors inserted into the circuit that are rated half that of the overcurrent device,
The conducting elements of the transfer switch are only rated at 400 amps and this matches a standard overcurrent device (240.6) therefore it must be protected at not more than its rating of 400 amps.
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Thanks for your help this afternoon. I talked to my boss this evening with the references we discussed, but he said they canceled their pow-wow for tomorrow after deciding to change the 800 amp main to a 400.
 
you know what they say, when in doubt, whip it out. if your not sure about proper protection being necessary but your gut tells you it is, you should do it and be safe than sorry.
 
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