Marc Posted October 4, 2010 Report Share Posted October 4, 2010 Of course, I've always understood that an undersized cable is a bad thing, but I always figured that too much power coming in, un-checked by a main breaker properly sized for the breaker panel, could be a big problem too. 'Undersized service cable' and 'too much power coming in' are the same issue, stated two different ways. Marc Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 4, 2010 Report Share Posted October 4, 2010 'Undersized service cable' and 'too much power coming in' are the same issue, stated two different ways. Marc Well, it could be the same thing, but I'm more wondering if anything bad could happen if for instance, you DID have a cable coming in rated for 400 AMPs or 320 AMPs connected to the bus of a panel rated for 200 AMPs, with no main breaker (and six throws shut off everything). Could something BAD happen in this setup, or is it just peachy? I always figured SOMETHING bad could happen. I'm not sure what, but just wondering... Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 4, 2010 Report Share Posted October 4, 2010 'Undersized service cable' and 'too much power coming in' are the same issue, stated two different ways. Marc Well, it could be the same thing, but I'm more wondering if anything bad could happen if for instance, you DID have a cable coming in rated for 400 AMPs or 320 AMPs connected to the bus of a panel rated for 200 AMPs, with no main breaker (and six throws shut off everything). Could something BAD happen in this setup, or is it just peachy? I always figured SOMETHING bad could happen. I'm not sure what, but just wondering... The only bad thing would be that someone would have spent too much money on the cable and there would probably be a funky connection where the large cable attached to the panel. Apart from economy & making up the connections, there is absolutely nothing wrong with using wires that are too large in any part of an electrical installation. In fact, from the perspective of voltage drop, it would be a good thing. The wires don't *force* the electricity into the house. The appliances *draw* what they need. I think you might be under the impression that the larger wires might somehow increase the voltage and push too much current through the system. This is not the case. - Jim Katen, Oregon Quote Link to comment Share on other sites More sharing options...
kurt Posted October 5, 2010 Report Share Posted October 5, 2010 What's amazing, is that after all this time, I still didn't know how to read a meter correctly.[:-paperba Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 5, 2010 Report Share Posted October 5, 2010 I suppose you're right, Jim. That has been my, apparently invalid, concern that can finally be dismissed. Thanks Jim and Marc for hammering that understanding home. I get it now. [:-graduat Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted October 5, 2010 Report Share Posted October 5, 2010 For what it's worth, today's inspection has two, less than half full, 225 AMP Cutler-Hammer panels with 200 AMP main breakers on a 320 CL meter. "And, that's the way it was - Tuesday, October 5, 2010." Quote Link to comment Share on other sites More sharing options...
hausdok Posted October 5, 2010 Report Share Posted October 5, 2010 Yesterday's inspection had a 200 amp panel for the house and next to that a 200 amp disconnect that used to be connected to an electric boiler. Since the boiler has been replaced with a gas boiler, the cable and conduit had been disconnected from that disconnect and the disconnect was turned off and labled "Don't use" although turning it on wouldn't have made any difference. Beneath the two meters was an unsealed gutter and next to them was a large sealed gutter. In the unsealed gutter, 500 kcmil cables coming from the sealed gutter that are spliced to the two sets of 3/0 copper cables feeding power to those two panels indicate that it's a 400 amp service. One couldn't tell the service size by looking at the meter because there were transformer coils like those described by Jim above around the cables in the unsealed gutter. The meter had a very low CL classification (I forgot to note the number and have forgotten it now) and the meter was labeled (if memory serves) 35 volts. I wrote it up as a 400 amp service with a 200 amp panel fed by a 3/0 copper SEC rated for 225amps but limited by the main disconnect in the panel to a maximum of 200 amps. ONE TEAM - ONE FIGHT!!! MikeI Quote Link to comment Share on other sites More sharing options...
Marc Posted October 6, 2010 Report Share Posted October 6, 2010 Looks like the right call. Marc Quote Link to comment Share on other sites More sharing options...
kimball gray Posted October 6, 2010 Author Report Share Posted October 6, 2010 I guess the question I have for the original poster is whether or not there was a gutter that wasn't sealed near the panels where he could have seen the service conductors feeding the panels. Most of the larger services I see around here have underground laterals because they are in neighborhoods where everyone wanted the power below grade. In upper end neighborhoods with very large homes, I occasionally find multiple panels with a gutter and inside the gutter I find larger cables bringing power to those panels. I have included a couple of pics. I appreciate the replies and input into this forum. Great responses and insight to you all, Thanks Click to Enlarge 55.74 KB Click to Enlarge 72.37 KB Click to Enlarge 72.77 KB Quote Link to comment Share on other sites More sharing options...
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