Hello, I'm a GC in the Bay Area. We are building an ADU and have had a very difficult time finding an exterior subpanel that meets our needs. The owner does not want the subpanel located inside the ADU. I've suggested to my electrician that we purchase and interior subpanel, flush mount it and build a water proof exterior closure. Are there any code issues here? Any other reasons not to do this? Thanks for the replies.
Exterior subpanel
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mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
Probably because the indoor panel in the picturre wasn't located inside a waterproof exterior enclosure as the OP is suggesting.
If an Indoor panel is located inside a waterproof exterior enclosure I see no reason that the panel couldn't be considered indoors.
JAP>
sfav8r
Senior Member
- Location
- San Francisco Bay Area
A couple of thoughts. First to directly answer your question, I don't see why an interior panel couldn't be mounted as you suggest.
The HO can't just mount the panel in the hall and hang a picture over it? Behind a bedroom door?
You can hide panels many ways. Even in a closet if it is a "dedicated electrical closet" and labeled accordingly. We have installed the panels recessed in a room and then had the GC make a decorative door. There are lots of options.
Finally, I checked out local big box store and they had a 30 space exterior MLO panel for $199. There are 12 in stock. Seems like it shouldn't be an issue to get something that would work.
The HO can't just mount the panel in the hall and hang a picture over it? Behind a bedroom door?
You can hide panels many ways. Even in a closet if it is a "dedicated electrical closet" and labeled accordingly. We have installed the panels recessed in a room and then had the GC make a decorative door. There are lots of options.
Finally, I checked out local big box store and they had a 30 space exterior MLO panel for $199. There are 12 in stock. Seems like it shouldn't be an issue to get something that would work.
There used to be a 3R door kit that was used on mobile homes to allow a indoor panel to be mounted between the studs & be accessed from the outdoors, it was rather cheesy but it did work. MH's, tract homes, & apartments are the apex of cheap. Have seen a 3R loadcenter where they mounted it between the studs & used flashing tape to seal it to the stucco lath, not sure how it's fared but I had nothing to do with it. They also did the same thing with a 2 gang meter can on the duplex across the street from my rental.
Somewhere I have a photo of how they were sealed to the stucco lath, but think it's on Photobucket & they have been ruined, changed from Jpeg to another format, need to just delete them & be done with it.
Here is a link from 2008 where this came from at another forum. https://www.electrical-contractor.n...1/wood-butchery-and-hack-electrical-fest.html
Somewhere I have a photo of how they were sealed to the stucco lath, but think it's on Photobucket & they have been ruined, changed from Jpeg to another format, need to just delete them & be done with it.
Here is a link from 2008 where this came from at another forum. https://www.electrical-contractor.n...1/wood-butchery-and-hack-electrical-fest.html
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
Detached ADU would need a disconnect, so MLO a wouldn’t fly, unless you used a back feed breaker and hold down kit.
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
Funny you mentioned that ... This is a picture of the ADU panel cover removed !
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Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
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- EC and GC
Man that’s sloppy, too. 
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
I have used NEMA 3R load centers and recessed in an exterior wall for small cabins. Obviously you would keep the conduit or NM cable entries to the rear of the load center, and they are behind the exterior wall finish
I am not sure about building an enclosure over the panel, others may know
I am not sure about building an enclosure over the panel, others may know
AC\DC
Senior Member
- Location
- Florence,Oregon,Lane
- Occupation
- EC
3r recessed seems the best. I guess its all up to the inspector, I would think if would have to Seal up such as a Door.
I've been looking at that one, but it is out of stock and currently unavailable.
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
In California they have a ADU (Acessory Dwelling Unit) & JADU (Junior Acessory Dwelling Unit). You have the option to have a separate address and electrical service, it's your choice. But the electric panel must be close to the service. The JARU is for converting a bedroom, which is less restrictive, except it requires a separate and dedicated access with a kitchen cooking facility with a sink. No bathroom required.
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
Don’t see what the relevance of that is.
Separate structures must have a disconnect located at the separate structure. That’s why I posted the Code references.
I know I would never get away with an MLO panel on a separate structure, unless I added a disconnect.
Separate structures must have a disconnect located at the separate structure. That’s why I posted the Code references.
I know I would never get away with an MLO panel on a separate structure, unless I added a disconnect.
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
That in part looks to be result of all those pigtails from AFCI/GFCI breakers. They can get real nasty if you don't take the extra time to clean it up.Man that’s sloppy, too.
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
This is just my opinion but I would think the panel would have to be listed for its use. Building your own weather-proof enclosure around an indoor panel would place the pass/fail decision squarely on the EI. That said, if you installed a Hoffman outdoor Nema 3R enclosure with a hinged door and then installed the indoor breaker panel within that enclosure I suppose that would be OK. But, again subject to the EI's discretion. I would ask him first before assuming it would pass inspection.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
I don't see how the above is subject to discretion. A panel is just a panelboard (the guts) inside an enclosure suitable for the environment. If the NEMA 3R enclosure is suitable for the environment, and the panelboard is inside it, I don't see how the presence or absence of an intervening NEMA 1 enclosure is material.
Cheers, Wayne
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Indoor = listed for indoor use
Outdoor = listed for outdoor use
Does putting an indoor listed panel in a NEMA 3 enclosure make it outdoor listed ? Just sayin'. While I've been a 3rd party inspection advocate, EI's seem to come up with the weirdest reasons to fail a job.
Outdoor = listed for outdoor use
Does putting an indoor listed panel in a NEMA 3 enclosure make it outdoor listed ? Just sayin'. While I've been a 3rd party inspection advocate, EI's seem to come up with the weirdest reasons to fail a job.
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Yes, as the "listing" for the "panel" is just for the enclosure of the panelboard, not the panelboard itself. So providing a NEMA 3R enclosure means the panelboard inside your "indoor panel" is now in an enclosure suitable for its environment.
Again "panelboard" = "panel guts", without any enclosure. To my understanding, the panelboard listing is not dependent on the enclosure.
Cheers, Wayne
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
I was under the impression that a panel gets sent to and then gets listed by UL as a complete unit. That means an indoor or outdoor panel and its respective enclosure is sent to UL and gets listed as such. If you pull the guts out of any one panel and install it into another you lose the listing IMHO (if that's what you meant).
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