Electrical subpanel- wire directly to meter?

So how are the service entrance conductors sized? If the ampacity of the service conductors is less than the sum of the ratings of the main breakers on the three main panels, then the only thing protecting the service conductors from overcurrent is the statistical unlikelihood of all three services drawing maximum power simultaneously?

Thanks, Wayne

The NEC doesn't require the main service conductors to be equal or greater than the sum of the up to six main disconnects. It does however require the calculated load to be less than the size of the service conductors

Wayne,

I installed a 200A panel in our garage, and another 200A panel in our house. Each panel is supplied with three 4/0 aluminum conductors that connect to the power companies junction box. Our pump house only has two breakers, 20A for the pump, and 15A for the lights. It has been many years since I hooked that up, but I think I used three 1/0 copper conductors for that panel.

The cable between the junction boxes and the transformer at the road was provided and installed by the power company. I wasn't here when they hooked us up, so I don't know what kind of cable they have on their side. When we hooked up our house, I asked the power guy about the cable, and he made a comment that their cable was a little undersized to be powering all three buildings. But he said that was done routinely a few years ago before they started running load calculations. He said it wasn't a big problem, since we were unlikely to max out all panels at once, but we may notice dimming lights if I was powering up equipment in the garage while the heaters were running in the house or something.

But, in the 15 years or so we have lived here, I've never noticed any problems with dimming lights, or any other signs of too much current draw.

Anthony

They are sized by the load calculation adding any allowance desired for future changes.

So nothing protects the service conductors from overcurrent. This surprises me, but I guess if the main service conductors overheated due to overcurrent, they are far less likely to start a fire in an enclosed space compared to a branch circuit or feeder. I suppose that is also the the reason that the distance the service conductors can travel within a building before the main disconnect is restricted.

Cheers, Wayne

It's surprising to me as well. Usually the NEC seems to overprotect wiring and equipment. Every time I, as an electrical contractor need to add a load to one of these types of services, I have to do a load calculation, just to be sure that the homeowners and electricians before me, didn't overload the mains

I'm running new circuits to a shop . The 3 wires coming into the meter are 2 hots and a ground or is the ground a nuetral

Yes.

You should have a ground rod into the ground, usually near the meter box.

It's a neutral. The fact that you have to ask suggests that there are probably code related issues involved here that you need to be aware of to do it safe and code compliant.

This thread has been going on since the Bush administration and I doubt it is still the same job so maybe this poster should tell us a little more about what he is doing.

As per code NEC 250-23(b), 250-24(b). The building's grounded electrode must connect to the main ground wire which connects to main neutral wire which connects to the the back of the panel.