Does US electric code allow branching ?

[Externet]

Hello.
My energy meter feeds the 'loads center breaker box' with 20 feet of conduit.
Would like to tap/connect another short branch from the same meter out to a second box 4' nearby with another conduit. Is that allowed ?

Meter 240VAC out==================================================100A multi breaker panel
               \======single 30A breakerbox

 

[rjenkinsgb]

I'm not in the USA, but I very much doubt that is permissible.

The safe way to do it is add a 30A circuit from the existing distribution board, so the protection of that is handled by both the main breaker and the branch output breaker.


Whatever you add to a mains system must be capable of both handling and breaking the full current from whatever feeds it.

ie. Anything feeding from the meter must be capable of handing fault currents in case of a short.

The upstream system (pole transformer etc.) will have fuses to protect the cable feeding the meter and through to the 100A distribution board.

The extra branch would need the same ratings, so the cable cannot overheat in case of a fault, and have an incoming breaker rated for the same fault current as the one in the main panel. They have to break the worst-case fault current, which may be thousands of amps for milliseconds, without any possibility of the contacts welding rather than opening).

 

[jpanhalt]

I suspect it is allowed and quite common in areas with separate garages and/or other outbuildings. Last time I looked at the condensed code books (e.g, Home Depot and Lowes) there were instructions for doing that. A separate ground may be required, if it's a building with outlets. 30A is about what a water heater or dryer may draw. What you seem to be proposing is no different than putting the water outside your back door.

In my case, the barn, which is about 150 feet away, has a separate meter, grounding, etc. and over 100A service. That was required at the time, probably by the high current needs. It's a pain because of the minimum billing per meter, and I don't meet that in the Winter. A detached, wood burning boiler for heat is just a branch circuit. It's about 50 ft away.

EDIT: My error. I misread the original post and now see that the proposal is to branch before the main switch. I thought the intent was after the main switch, which is why I made analogy to a water heater, etc. Why not do it after the main switch? If you do that, the breaker for the branch might require a lock out, which is a very inexpensive addition.
EDIT2: This "code" seemed to indicate the branch came after the main breaker:

 

[ZipZapOuch]

No. You need a single mains switch to throw to cut all power. There is no way to add your panel without asking the power company to shut off the meter ( you'll pay a disconnect + reconnect charge and your local code may not approve because there is no single switch. Add a sub panel to the main box.