Panel on underside of sloped roof rafters

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tonype

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Is a panelbox allowed to be installed on the underside of roof rafters so that it is not vertical (faces downward about 30 degrees
 

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I can't think of anything in NEC that specifically addresses this, or even to face it up.

Listing/instructions may require it to be "vertical".
 
jumper said:
Ah, 110.26(3). Floor to ceiling height. Is this a dwelling unit? Exception may apply.

Assuming attic has finished floor, no?
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I think the issue you raised of headroom is relevant.

There is no difference in existing dwelling units roof rafters (head room) than new construction roof rafters (headroom).

If this panel is a new install and you do not have the head room required, that could be an issue.
 
Hmmmm....

If one interprets the working space to require 6.5ft of headroom below the panel, then the install cannot be compliant with both 110.26(3) and 404.8(A), which puts a height limit of the same dimension on circuit breakers used as switches.
 
jaggedben said:
Hmmmm....

If one interprets the working space to require 6.5ft of headroom below the panel, then the install cannot be compliant with both 110.26(3) and 404.8(A), which puts a height limit of the same dimension on circuit breakers used as switches.
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jumper said:
Below the panel?

See existing resi exception. 110.26(3)
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I think he is onto something,rember OP said this panel is ~30 degrees from vertical.

Though I can see an issue with working clearances with a 4 ft tall cabinet in that situation, where a small 6 or 8 circuit loadcenter might not have the same issue.

You do need the head room but part of the headroom is bordered by the item you need clearance for.

30 degree angle would be little less than 6/12 pitch roof. If you had a 30 inch tall cabinet mounted at this angle the highest point is about 15 inches above the lowest point, the furthest rear point is about 26 inches further back then the furthest forward point.
 
jumper said:
Below the panel?

See existing resi exception. 110.26(3)
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Presumably the intention of the headroom clearance is that most people have ... headroom ... to stand in front of the panel while working on it. If the panel is overhead then it makes sense that the headroom is the space below the panel. Otherwise a person can't stand up straight while working in the panel, and the intention of the working space requirement is not met.

As far as the resi exception, now that I look at it again it is awfully broad language, I wonder if the language actually reflects the intention. (BTW, San Francisco has a local amendment deleting this exception in its entirety.) I agree with you on a strict reading of the language, but I don't think that the intention was to allow panelboards to be installed above 18" high crawl spaces, for example.

For commercial I would still say that an overhead panel cannot be compliant. Perhaps if installed in wall that is closer to vertical one can allow a reasonable interpretation. 30 deg off vertical is pushing it, in my opinion. OP is unclear if it's 30deg off vertical or horizontal, I would bet horizontal on the percentages.
 
kwired said:
I think he is onto something,rember OP said this panel is ~30 degrees from vertical.

Though I can see an issue with working clearances with a 4 ft tall cabinet in that situation, where a small 6 or 8 circuit loadcenter might not have the same issue.

You do need the head room but part of the headroom is bordered by the item you need clearance for.

30 degree angle would be little less than 6/12 pitch roof. If you had a 30 inch tall cabinet mounted at this angle the highest point is about 15 inches above the lowest point, the furthest rear point is about 26 inches further back then the furthest forward point.
Click to expand...

30* from vertical would be a 60* pitch, which is like 20/12 or so. 12/12 is a 45* pitch.
 
JFletcher said:
30* from vertical would be a 60* pitch, which is like 20/12 or so. 12/12 is a 45* pitch.
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correct, I screwed up there and gave measurements for 30 degrees from horizontal. You still have similar issues like I brought up, just not quite as severe as my examples.

I think 110.26 working clearances assume vertical/near vertical equipment.

Next question is can panelboard be completely horizontal (face up or face down)? If not what angle can it be before it is considered vertical?

Still haven't looked into it but I still kind of have a feeling instructions or even general listing standards will require vertical mounting.
 
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