Thread: Junction box off of a main panel, can I do this?

I don't want to waste anyone's time here, I'm just a homeowner. But I need a little help. I have a lot of experience with simple residential electric situations. Just not this one. My two bathrooms are on the same circuit and I want/need to separate them. The main panel is in the garage mounted flush in the stud wall and everything is drywalled. I'd like to open the wall once for this and any other future additions or changes to the system. What I want to do is run an 1-1/2" conduit out of the main panel, up into the attic and then mount a sub panel there. That way, any time I need to run a new circuit, I can pull it to the sub panel and then easily distribute it out to wherever I want to go with it. Also, everything in the house Romex. No conduit. Anything new out of the new panel would probably be in EMT.

Thanks in advance for your help.

Similar Threads:

• Charred Copper wires in Main Panels
• Transformer & Low Volt Wiring in Main Panel
• Chimney Fire Extinguished At Landmark Home On Main Street - Newtown Bee
• General Electric Split Main Panel
• Double at Main

I probably wouldn't put the box in the attic, unless you have a large attic with easy access to the area where the panel would be. There are some work space requirements that will need to be met. I would probably put the panel in the garage, and run some pipe and/or extra wires up to the attic for future electrical needs. You could then distribute out from there to wherever you wanted to.

Jim,

Jim is correct (this name thing is going to be difficult ). Electrical panels must be readily accessible. Put the panel in an accessible location and install conduits for future wiring.

Sounds like a 60A circuit would be plenty. No need to install something small just to save a few bucks. Make sure you run a four wire feed so that you can have the neutrals and grounds on seperate busses in the new panel. 6/3 copper with ground will be good. Some of the 6 gauge copper cable is really only rated for 55amps though so check the temperature rating on it or just use a 50 amp circuit and buy the cheaper cable. JR's advice about putting the panel in the garage is really good, just make sure you put several conduits up to the attic.

I have plenty of room in the attic. I can walk down the center of it, which is where some of my other problems are. I used to do a lot of new electrical construction it the Chicago area. It was all in EMT and placed in a nice neat manor. My house has all Romex and there was no rhyme or reason where they ran it in the attic. I hate that. Very un professional as I see it, but maybe that is normal. I have been up there a lot lately because of a bathroom remodel. And I invariably step on the Romex because they ran it right where someone would walk. Anyway, this new junction box will not have breakers. It will be just an aid in pulling anything new from the panel. I have 6-8 open breaker locations at the main panel. I could even mount the new junction box on the wall the builders built to separate the garage attic from the main house attic.

Thanks again gentlemen.

Jim

Originally Posted by Jim Bjork

I used to do a lot of new electrical construction it the Chicago area. It was all in EMT and placed in a nice neat manor.

That's all well and good in a manor, but could you wire in this manner in a squalid hovel?

"Re: Junction box off of a main panel, can I do this?"

CAN you do that? Yes. People do that all the time, so, yes, it "can" be done.

Are you ALLOWED to do that? No, not unless the attic is truly accessible and not unless there is a full walkway floor to the panel working space and there is a full working space floor in front of that panel, and the walkway to, and working space at, the panel are of sufficient size.

[quote= .....not unless there is a full walkway floor to the panel working space and there is a full working space floor in front of that panel, and the walkway to, and working space at, the panel are of sufficient size.[/quote]

Now I understand. Thank you.

Jim Bjork

Originally Posted by Jerry Peck

and the walkway to, and working space at, the panel are of sufficient size.

Jim,

Just clarifying what the above refers to: "size" refers to clear width and height of the walkway space as well as area.

The working space in front of the panel is required to be 30" wide by 36" deep in front of the panel. The walkway should be at least 24" wide, but if you fit it parallel between 24" on center trusses without going through webs that should work out 'close enough' (it is rare that you will hear me say that something is 'close enough' as everything really should be "right", "close" only counts in horse shoes and hand grenades), the floor needs to be the same as for the rest of the house - no flimsy plywood, needs to be strong enough to properly and adequately support you and not be a trampoline.

"close" only counts in horse shoes and hand grenades.........

Don't forget nuclear weapons..........I'm a former Air Force B-52 weapons troop.


no flimsy plywood, needs to be strong enough to properly and adequately support you and not be a trampoline.

Shoot, I have the flimsy plywood trampoline installed.

I think coming out of the panel and mounting the junction box on the garage wall looks to be my best option. It just means that any EMT that I run out of it will have to go up through the ceiling drywall.Unless I replace the trampoline in the attic.Though that might be easier in the long run.

I uploaded a picture. If I put the junction box in the garage, can it be up high above the panel, or should it be next to it at the same level? Remember, no breakers just basically an access panel.

Thanks.

Because I can see you running one raceway (conduit) up to the attic and then stuffing it full of NM cables, then not addressing conduit fill or derating (derating would be the real killer for that), I would suggest this: Where you have that drywall cut out ... install a slightly larger piece over it to ensure a seal to the existing drywall and to maintain the separation wall between the house and the garage, install a decent looking frame around it, and use that as your access panel and simply remove that access panel whenever you need to run another circuit.

Solves all kinds of problems you may likely create by doing what you were going to do, and, makes it easier and less costly too. Hard to beat that.

Because I can see you running one raceway (conduit) up to the attic and then stuffing it full of NM cables, then not addressing conduit fill or derating

Never, not ever would I do that. I hate NM cable in the first place. To expound a little further. I worked on B-52 weapons systems. If there is one thing that I learned is attention to detail. Another, do it right or else bad things happen. I was going to run wire in EMT to anything new that I install in conduit out of this new junction box.

Now I have to ask this question. Why is my situation so different than running 3/4" conduit from a main panel into a square or octagon box in the attic? Then running three circuits to the box and then splitting them off in three directions? That' is done everywhere, isn't it. That small box doesn't need the attention that my larger box needs. Essentially I want to do this with a larger conduit and a larger box in the attic.

I do like the idea of building out the wall above the panel. I never would of thought of that. That is why I posted on here. I knew there were people out there with answers.

Thanks for all of the help!

Originally Posted by Jim Bjork

Now I have to ask this question. Why is my situation so different than running 3/4" conduit from a main panel into a square or octagon box in the attic?

Jim,

I took this ...

Originally Posted by Jim Bjork

Anyway, this new junction box will not have breakers. It will be just an aid in pulling anything new from the panel. I have 6-8 open breaker locations at the main panel.

... as an indication that you might run 6-8 new circuits up that 3/4" conduit.

That would not only give you real conduit fill problems but 8 new circuits would give you 16 current carrying conductors, which run into the attic and would need to be derated for ambient temperature first.

Take #12 AWG NM-B cable, the ampacity rating for derating purposes is 30 amps.

Let's presume that in your area the attic temperatures can get to 130-140 degrees F (not unusual for attics in the heat of summer). The derating factor for ambient for that temperature is 0.71, or 71% of the ampacity of 30 amps, making a derated ampacity of 21.3 amps.

Now we need to derate for the number of conductors in the raceway or lack of maintaining spacing for 24" or greater. With 8 new circuits, 16 conductors, in that conduit, regardless of whether you gave up trying to use 3/4" and put in 3" conduit, the derating factor for 10-20 conductors is 0.50, or 50%. That would mean that the derated ampacity of 21.3 amps would be derated again, down to 10.65 amps. That means you would need to put a 10 amp breaker as protection for those conductors.

If you only run 1 new circuit up the 3/4" conduit to the junction box, then you would need to completely forget about "I have 6-8 open breaker locations at the main panel." as you would only be able to use one circuit in that conduit. If you tried to sneak in two #12 AWG NM-B cables, you would have 4 current carrying conductors, and 4-6 conductors in that raceway would require derating to 80%. That derating is not from 30 amps, that derating is from the derated 21.3 amps for ambient derating, leaving you with a derated ampacity of 17.04 amps - you would not be allowed to use a 20 amp breaker, you could, however, use a 15 amp breaker for that, but you would want to mark in some manner that a 20 breaker is not allowed so that neither you nor any future owner replaces the 15 amp breaker with a 20 amp breaker, thinking 'Hey, it's #12 AWG NM cable, and that's good for 20 amps ... ' - that would not be good.

Thread titled "junction box off of a main panel, can I do this?"

Although your first post went on about a panel in the garage attic, I'm addressing your post title and what you also said in subsequent posts here:

Of course you can have a pull box or junction box, as long as it has an accessible cover plate, is of sufficient size, and not covered with building surfaces. It seems you are describing using a cabinet or box (not a panel) for this purpose.

You don't need a walkway or six+ feet of height for a mere junction or pull box in the attic or in the garage! You can home run via the junction box, no problemo.

Obviously SOMEBODY is fixated on the idea you would run multiple NM in EMT....Obviously not your intention, as you have already said you dislike NM and are familiar and comfortable with pulling conductors in conduit.

Go right ahead and pull THHN in conduit, or better yet pick a 90 c or better with a W indication since in unconditioned space, abide your fill and derating.

Condulet or conduit off the panel cabinet to your "box" or cabinet, be sure to seal for condensation from unconditioned attic, and before reentrance to conditioned space and do your fire/draft stopping/blocking on the exterior. And don't forget to grab the appropriate clamps for your existing NM running out from your "junction" box/cabinet.

If (and apparently you do have six or more spaces available) you have the room in your panel, and it really IS "available" to be used, can't think of a reason to have another "panel". No mention of any other reason (v.d., circuit length, bus rating limits, stab ratings, etc.) to need another panel, YET.

However, just because a space is unoccupied by a breaker on an existing panel doesn't necessarily mean it is "available" to fill (as to rating and listing/labeling) for use. If you are looking to feed a panel, keep it in the garage, adjacent, not in the shared attic, heck move the garage circuits to the fed panel, and homerun the house via a junction "box".

Originally Posted by James Risley

Or consider running 6 or 8 or more 3/4 or 1 inch empty conduits from the existing panel into the attic to a location accessable in the attic. Later as needed you can extend each empty conduit to its own location and then pull all the wires all the way from the panel to the point of use.

If the drywall above the panel is kept as a removable cover, I see no real need to install a lot of empty conduit, and space is limited there. I would personally just pull the new NMD to the bathroom and be done with it.

I think the OP has his answer - Yes, you can do that, if the box in the attic is merely a junction box without breakers. You will need to drill a large hole in the wall plate for that 1 1/2 conduit, and some of the existing wiring may need to be moved.

Thanks for all of the help. A few good ideas posted. I realize that I used the wrong term in my original post. "Sub panel" was used when it shouldn't have been. That got some people going off in the wrong direction. I think I know more than I actually do sometimes.

Jim Bjork