sub panel main breaker

[stew]

when is a main breaker required in a subpanel?

 

[mdshunk]

Never, if it's in the same building as the panel that's feeding it. You need some kind of main if it's in a detached structure with more than 6 branch breakers. Always, if the specs require it.

 

[jwelectric]

What if it is in a detached building and has six single pole 15 amp breakers?
Will the panel require a main if there were six single pole breakers?
How would you suggest fulfilling the requirements of 225.30 through 225.39?

 

[suemarkp]

Doesn't 225.33(A) and 408.36(A) Exception 1 answer most of your issues.

 

[buck33k]

How about 230.92?

Say you have an apartment building where the service overcurrent devices are locked or sealed. Would'nt a main be required in the "sub-panels?"

In reading 230.92 it seems in the above case the downstream OCP would have to be of a lesser rating, for instance if the locked service disconnect for an apartment were 80 amps, the panel main would have to be 70 amps. Am I on the right track?

I worked on an apartment building recently that had the service disconnects outside but because of their location I would think the occupants would have a hard time determining which theirs was and where they were. In this case, would it be a good idea to supply a main in each apt panel?

 

[jwelectric]

Doesn't 225.33(A) and 408.36(A) Exception 1 answer most of your issues.

Here in lies the question, does it answer all of the questions?

 

[LarryFine]

In reading 230.92 it seems in the above case the downstream OCP would have to be of a lesser rating, for instance if the locked service disconnect for an apartment were 80 amps, the panel main would have to be 70 amps. Am I on the right track?

Yes and no. Don't confuse the requirements for access to the service disconnect and the OCP device.


230.70(A)(1) Readily Accessible Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.

230.92 Locked Service Overcurrent Devices. Where the service overcurrent devices are locked or sealed or are not readily accessible to the occupant, branch-circuit overcurrent devices shall be installed on the load side, shall be mounted in a readily accessible location, and shall be of lower ampere rating than the service overcurrent device.

 

[buck33k]

"Yes and no. Don't confuse the requirements for access to the service disconnect and the OCP device."

Larry,
Not quite following you. Was the 80amp / 70amp example not an accurate use of 230.92?

Thanks in advance.
Buck

 

[LarryFine]

Yes, but it does not allow locked/inaccessible disconnects, only OCP devices.

 

[iwire]

Yes, but it does not allow locked/inaccessible disconnects, only OCP devices.

???

A service or feeder disconect can certainly be behind locked doors.

I am not following you.

 

[LarryFine]

230.70(A)(1) Readily Accessible Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.

Doesn't locking out an occupant interfere with "readily accessible"?

 

[roger]

Doesn't locking out an occupant interfere with "readily accessible"?

Larry, a lock does not affect the "readily accessible location" as worded in 230.70(A)(1)

Roger

 

[iwire]

Doesn't locking out an occupant interfere with "readily accessible"?

If it does than no home or business could have an indoor service disconect.

 

[LarryFine]

Why not? The occupant has that access.

 

[iwire]

Why not? The occupant has that access.

Do they?

Does the tenant in a apartment building ave access to the main?

Does the tenant in an office building have access to the main?

Does the fire dept have keys to everyones home.

I am not sure which code section you are saying prohibits looked doors?

 

[buck33k]

One more follow-up question on this topic if I may:

Even if the service or feeder disconnects are accessable to the occupant, practically speaking, the average occupant might not know where they were located. In this case, would'nt it be a good practice to install a main in the occupant's panel? (although not required)

and -- each disconnect for a single apartment could be of equal value since they are not locked or sealed and are technically accessable?

 

[stickboy1375]

I used to confuse "readily accessible" also...

 

[LarryFine]

If it does than no home or business could have an indoor service disconect.

That home or business with the indoor disconnect certainly has access by the occupant.

Does the tenant in a apartment building ave access to the main?[/i]

That's not the same as a single-occupancy premises.

Does the tenant in an office building have access to the main?

Same response, and often not.

Does the fire dept have keys to everyones home.

Are they supposed to have ready access to disconnects? If so, then no indoor disconnects would be allowed, as you stated.

I am not sure which code section you are saying prohibits looked doors?

230.70(A)(1) to start with. Is the concensus here that a locked door does not interfere with ready access?

If so, then I'm wrong. Hey, it can happen.

 

[allenwayne]

One thing about the fire depts. they have a universal key,4 ft. long with a sharp edge and a pick on the opposing side.This usually opens any and all doors.

 

[stew]

well my original question concerned an existing subpanel installed in the downstairs of this residence, we want to add a 60 amp breaker for a 40 amp circuit to a heat pump. ok so far except that the 125 sub is fed wwith 60 amps and # 8 cu. I will refeed

the sub with 2224 al 100 amp sub breaker at the main. there are 6 circuits at the moment lightly loaded 20 and 15 amp primarilay feeding the office and additional computer equip. the havc breaker makes 7 total in the sub. No extra main required as I see it. Interesting discussion so far tho