New Dwelling Unit Panel fed from a House Panel

[Misheru]

I have a project where an existing manager's office is being converted into a new ADU. The new unit panel is fed from an (E) house panel because per the designer, there are no more meters available for use. Is there a code section prohibiting this? Any concerns about this design aside from bills/metering?

Thank you!

 

[JoeStillman]

It's not a violation of the NEC to feed a dwelling unit from the same meter as some common "house" circuits, but different states have rules about how you're allowed to feed dwelling units. I don't know about CA, but in NJ that would not be allowed. In PA it would.

 

[Misheru]

It's not a violation of the NEC to feed a dwelling unit from the same meter as some common "house" circuits, but different states have rules about how you're allowed to feed dwelling units. I don't know about CA, but in NJ that would not be allowed. In PA it would.

Thanks for your response.

 

[jaggedben]

I know in San Francisco it's required to have a separate meter for common areas if there are different owners/tenants in the dwelling units for the other meters. I can't remember if that's a local or a state wide rule. So, if you have common areas and a new unit on the same meter that could be a violation, but I can't cite the code for you.

 

[wwhitney]

It's not a violation of the NEC to feed a dwelling unit from the same meter as some common "house" circuits,

2017 NEC 210.25(B) says:

"Branch circuits installed for the purpose of lighting, central alarm, signal, communications, or other purposes for public or common areas of a two family dwelling, a multifamily dwelling, or a multi-occupancy building shall not be supplied from equipment that supplies an individual dwelling unit or tenant space."

I'm a bit unclear on how broadly to construe the terms "equipment" and "supplies" here. The broadest interpretation would lead to the conclusion that the house loads need to be on their own meter.

Cheers, Wayne

 

[JoeStillman]

2017 NEC 210.25(B) says:

"Branch circuits installed for the purpose of lighting, central alarm, signal, communications, or other purposes for public or common areas of a two family dwelling, a multifamily dwelling, or a multi-occupancy building shall not be supplied from equipment that supplies an individual dwelling unit or tenant space."

I'm a bit unclear on how broadly to construe the terms "equipment" and "supplies" here. The broadest interpretation would lead to the conclusion that the house loads need to be on their own meter.

Cheers, Wayne

I always thought that meant you can't feed house loads from a tenant meter, but it doesn't say you can't feed tenant loads from a house meter.

 

[wwhitney]

I always thought that meant you can't feed house loads from a tenant meter, but it doesn't say you can't feed tenant loads from a house meter.

If 210.25(B)'s "equipment" includes a meter, and if "supplies" means supplies anywhere downstream, then it rules out a meter that supplies both house loads and tenant loads.

Cheers, Wayne

 

[petersonra]

If 210.25(B)'s "equipment" includes a meter, and if "supplies" means supplies anywhere downstream, then it rules out a meter that supplies both house loads and tenant loads.

Cheers, Wayne

The main disconnect for the whole property supplies everything. Your interpretation of this wording would prohibit house panels entirely

 

[Strathead]

I know in San Francisco it's required to have a separate meter for common areas if there are different owners/tenants in the dwelling units for the other meters. I can't remember if that's a local or a state wide rule. So, if you have common areas and a new unit on the same meter that could be a violation, but I can't cite the code for you.

From what I remember when I lived there, it isn't that separate meters are NEEDED, it is that you can't charge the tenant for power used, that is selling electricity. You can have a flat rate rent that includes "free" utilities. If that makes sense.

 

[wwhitney]

The main disconnect for the whole property supplies everything. Your interpretation of this wording would prohibit house panels entirely

There's no requirement to have a single main disconnect for a building. The house loads could be on a separate meter with its own disconnect. I'm not necessarily endorsing this interpretation of 210.25(B), it just looks like the obvious place to draw the line.

If 210.25(B) instead said "branch circuits . . shall not originate in equipment . . ." then it would be clear where to the draw line. The branch circuit originates in the panelboard with the branch OCPD, and so panelboards with house branch circuits would be prohibited from also supplying tenants/dwelling units.

But the language is not "shall not originate" it is "shall not be supplied". Clearly that means the prohibition extends farther upstream than just the panelboard in which the house branch circuits originate. I see no other place to draw the line other than extending the prohibition all the way to the service point.

Cheers, Wayne

 

[jaggedben]

From what I remember when I lived there, it isn't that separate meters are NEEDED, it is that you can't charge the tenant for power used, that is selling electricity. You can have a flat rate rent that includes "free" utilities. If that makes sense.

That's really a different issue, involving enforcement of tenants rights which may not even involve the building department, and where you don't have separate meters for every unit. You'd find that on older housing with (illegally) converted or divided units, but I doubt they would allow that for new construction. If you do have separate meters for each unit, you must also have a separate meter for the common areas. If you are building a new unit or upgrading the service I think the building department is likely to make you install the correct number of meters. I understand that there are other more complicated options (e.g. master meter) but the bottom line is that I don't think the OP's design would fly in SF.

 

[jaggedben]

There's no requirement to have a single main disconnect for a building. ...

But 'equipment' is so broad that it could apply to all loads served by a single service.

I think the key word in the code section is 'individual' dwelling unit or tenant space. The intent seems to be that common area branch circuits not be supplied from a panel that only one tenant has access to. However the way it's worded, to my reading, prohibits mixing common area branch circuits on the same panel or feeder as a single unit, but not on the same panel or feeder as multiple units. (So, I pretty much agree with you.)

I always thought that meant you can't feed house loads from a tenant meter, but it doesn't say you can't feed tenant loads from a house meter.

The NEC does not make that distinction, because it doesn't care who pays for the meter. Any equipment (separate meter or not) that supplies common area branch circuits along with an 'individual' (not multiple) dwelling unit or tenant space would run afoul of the code section.

 

[wwhitney]

But 'equipment' is so broad that it could apply to all loads served by a single service.

Loads, yes, but the field installed service conductors are not equipment.

I think the key word in the code section is 'individual' dwelling unit or tenant space.

It is true that my earlier proposed interpretation does not apply any particular meaning to the word "individual" in 210.25(B). Reading "individual" as meaning "precisely one" does provide a less severe restriction. I'm leaning towards preferring this interpretation.

Still, that interpretation does also prohibit the configuration proposed in the OP.

Cheers, Wayne

 

[Strathead]

That's really a different issue, involving enforcement of tenants rights which may not even involve the building department, and where you don't have separate meters for every unit. You'd find that on older housing with (illegally) converted or divided units, but I doubt they would allow that for new construction. If you do have separate meters for each unit, you must also have a separate meter for the common areas. If you are building a new unit or upgrading the service I think the building department is likely to make you install the correct number of meters. I understand that there are other more complicated options (e.g. master meter) but the bottom line is that I don't think the OP's design would fly in SF.

Or Fairfield.