Mounting 4" square boxes in drywall question - flush subpanel to conduit transition

[Probedude]

Mounting 4" square box in drywall question - flush subpanel to conduit transition

I have a flush mounted subpanel in an attached garage that is semi-finished (the three walls of the garage are finished, the rafters above are not). I would like to add a surface mount (in a 4" metal box) nema 14-50 outlet on the opposite side of the garage, running conduit from the subpanel, across the bottoms of the rafters to the opposite side of the garage for a 220V welder.

In trying to figure out how to properly transition conduit through the drywall, reading this website and others, the suggestion was to use a 4" metal electrical box with an extension to connect the conduit through the drywall to the subpanel. Off to my local Home Depot and Lowes and I'm not seeing any stud mounted 4" boxes which allow for the 5/8" drywall thickness.

How would I secure the 4" box to the stud so it's flush? The largest box they had, the mounting holes in the side are not far enough back to screw into the stud AND allow the box to protrude out 5/8 ".

Also the extensions I'm seeing have rounded corners (they're drawn, not welded) so each corner there is a small gap. Is this a concern?

Thanks for your help.

 

[oltruckag]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Screw Gun Bracket? with a deep box and bend it to mount a shallow box. The box will then be approximately flush with the drywall.

Having a hard time visualizing what you are explaining - where do you want to put the box in the wall and use an extension ring to come outside of the wall?

If your not opposed to surface mount, just do a deep box offset and transition through the wall with the conduit itself and mud around it. Or cut a couple of holes in the drywall and just do a 90deg turnout?

Maybe a sketch or photo would help.

Also - why run on the bottom of the rafters? What if you want to add a ceiling later?

Tyson

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

You need a 6-50 for a welder. Fish 6/2 romex out the top of the panel, out the wall and into the back of a 2 1/8 deep 4" square box. Run 3/4 EMT up the wall across the garage ceiling and down the wall into another 2 1/8 deep box. Use a raised cover for the receptacle. Two number 6 and a number 10 ground wire in the conduit. Splice it to the romex and put blank cover on the 1st box.

The screw gun bracket won't work if the drywall is already in place. You can probably get the wire cut to length at HD or Lowes

 

[Probedude]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Screw Gun Bracket? with a deep box and bend it to mount a shallow box. The box will then be approximately flush with the drywall.

Cool! I didn't know those existed.

Having a hard time visualizing what you are explaining - where do you want to put the box in the wall and use an extension ring to come outside of the wall?

I was going to cut the drywall above the sub panel to bring out the new circuit and figured why not make a bigger cut and flush mount the 4" box to the 2x4.

If your not opposed to surface mount, just do a deep box offset and transition through the wall with the conduit itself and mud around it. Or cut a couple of holes in the drywall and just do a 90deg turnout?

Maybe a sketch or photo would help.

Also - why run on the bottom of the rafters? What if you want to add a ceiling later?

It's a California house, so no basement to store stuff. We store things instead in the garage 'attic' rafters. It won't ever get a ceiling.

I thought about coming right out of the drywall with conduit but wanted it to look like I knew what I was doing. Surprisingly search Google Images, I couldn't find any examples of what I wanted to do.

You need a 6-50 for a welder. Fish 6/2 romex out the top of the panel, out the wall and into the back of a 2 1/8 deep 4" square box. Run 3/4 EMT up the wall across the garage ceiling and down the wall into another 2 1/8 deep box. Use a raised cover for the receptacle. Two number 6 and a number 10 ground wire in the conduit. Splice it to the romex and put blank cover on the 1st box.

The screw gun bracket won't work if the drywall is already in place. You can probably get the wire cut to length at HD or Lowes

Appreciate the input! So I can surface mount the first 4" box to the drywall and
use a romex clamp from the back just through a hole in the drywall? That would make things easier and a smaller cut in the drywall to get a romex clamp on the top of the subpanel.

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

You can get a plastic snap in connector. It's a pain in the **** to get the wire through, but you can install it from inside the panel without cutting the drywall. Bring the romex out next to a stud. That way, the box can screw to it.

 

[mc4life27]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

You need a 6-50 for a welder. Fish 6/2 romex out the top of the panel, out the wall and into the back of a 2 1/8 deep 4" square box. Run 3/4 EMT up the wall across the garage ceiling and down the wall into another 2 1/8 deep box. Use a raised cover for the receptacle. Two number 6 and a number 10 ground wire in the conduit. Splice it to the romex and put blank cover on the 1st box.

The screw gun bracket won't work if the drywall is already in place. You can probably get the wire cut to length at HD or Lowes

In ca can't run romex in conduit if the run is longer then 10 ft. So run 4 single conductor 6g. Run wire up he wall to a metal box. Run 1 inch conduit just to make life a little easer to another metal box above where you want the outlet then run wire down the wall
Inside wall cavity into a double gang outlet box flush in the wall wire up outlet. Also I wouldn't bother with the plastic clamps with that thick of a wire just use some of the 2 screw metal clamps.


Sent from my iPhone using The Garage Journal mobile app

 

[Jim greengo]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

4 sq box with brackets welded on,whatever thickness of plaster ring you need to get it flush with where surface of drywall will be.

 

[sberry]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Also, what welder. Very few factory cord machines call for that big wire.

 

[alfredeneuman]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

In ca can't run romex in conduit if the run is longer then 10 ft.

No that's not a rule.
The CA Electrical Code is just the 2014 NEC verbatim, with the CA Energy Code added on

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

In ca can't run romex in conduit if the run is longer then 10 ft. So run 4 single conductor 6g. Run wire up he wall to a metal box. Run 1 inch conduit just to make life a little easer to another metal box above where you want the outlet then run wire down the wall
Inside wall cavity into a double gang outlet box flush in the wall wire up outlet. Also I wouldn't bother with the plastic clamps with that thick of a wire just use some of the 2 screw metal clamps.


Sent from my iPhone using The Garage Journal mobile app

It would probably be a better idea to read my post again. The romex is just to get into a box on the wall above the panel. It clearly states two number six and one number 10 in the conduit (sorry, I left out the THHN/THWN part). I have no idea where you think you would need 4 single 6g conductors. If it were a 14-50r (electric range/camper receptacle), it would be three 6's and a #10 ground, but I stated he needs a 6-50r for a welder. That would require two hot conductors (#6) and one ground. (#10) and I personally wouldn't pull a ground in the pipe. Just bond the romex ground at the first box and call it good.

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Also, what welder. Very few factory cord machines call for that big wire.

Correct, but if a 50 amp receptacle is used, it needs to have 50 amp wire.
I have Lincoln 180, I have never clamped it or nor have I checked the name plate. I am guessing it uses less than 20 amps when on the highest setting. The receptacle was already there when I bought the house. If I were installing a new receptacle in my garage for it, it would probably get #12 or maybe #10 conductor, but I would know that they are supposedly too small for 50a. (I also don't have a problem with code violations on my own stuff). One never knows exactly what the OP may plug into that receptacle in the future. It may be a small mig now, he may get a large ??? machine in the future.

 

[alfredeneuman]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Correct, but if a 50 amp receptacle is used, it needs to have 50 amp wire.

Again untrue. EDIT: in the case of welders and motors

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Again untrue. EDIT: in the case of welders and motors

I just looked it up in my trusty 2008 code book and I believe you are correct. It's an exception that might as well be worded with jibberish. In 25+ years I thought that the "mismatching" of wire size and ocp was only for hardwiring. However, the OP will need to have/know what welder he needs to size the wire and ocp. I assume he doesn't have it yet since he wanted to install a 14-50r. If it were me in his shoes, I would use the #6 just for the possibility of future upgrades

 

[Bert_]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

8thhn in pipe is 50A wire... No reason at all to run 6.

If it's just for a welder #10 will run nearly anything a hobbyist would want.

 

[alfredeneuman]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

You're an electrician and the most recent Code book you have is the 2008?
Lots of changes have happened in the last 3 NEC cycles (Iowa is on the 2017)

The rules for wiring for motors and A/C's have been the same for wiring sizes for more than 60 years

 

[sparky 1971]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

You're an electrician and the most recent Code book you have is the 2008?
Lots of changes have happened in the last 3 NEC cycles (Iowa is on the 2017)

The rules for wiring for motors and A/C's have been the same for wiring sizes for more than 60 years

Sorry to offend you. I never said 2008 was my most recent. I have a 2017 on my desk, the 2008 is under the seat of my truck. The code book I had before that was a 1993 that was issued to me when I started. I also managed to survive without a 2011 or 2014. That probably really upsets you, doesn't it? I am at the point in my career that I just don't care anymore. I am also aware that the State of Iowa adopted the 2017 code on Jan. 1, 2018. I am also really good friends with one state inspector and a city inspector. If I have any questions, all I have to do is call.

I know there are rules for motors and a/c's and given enough time, I could size them out of the book. I choose to use my Square D cheater card for motors and look at the nameplate for a/c's instead. I stated that I thought it was for hardwiring. I did not know that receptacles were included. I also gave you credit for being correct. If I made a mistake out of ignorance and oversized the wire to a receptacle, that's too bad for me. Maybe you have done something even more horrific like wrapped a ground wire around a box cover screw instead of using a bonding screw.

EDIT: I just looked and the code book on my desk is a 2014. I was honestly going to buy a 2017 when it went into effect, but I found a smoking hot deal on a 2014 so I bought it instead. It really doesn't matter. The 2014 is still wrapped in plastic unopened. A 2017 would share the same fate. Like I stated earlier, I just don't care.

To the OP, I apologize for giving you bad info. You can use #10 wire, but you still need a 6-50r.

 

[Probedude]

Re: Mounting 4" square boxes in drywall question - flush subpanel to conduit transiti

Thanks all for your help! You're right, I don't have a welder yet but looking at getting the Hobart 190 with the spool gun. Getting by with a HH 140 right now and finally looking to upgrade.

The 14-50r was for future proofing. There will likely be a BEV car in our future so I figure I might as well size it for that.

Picked up another 4" x 2-1/8" box today with cover, some 3/4" romex clamps and the big blue wire nuts for 6 awg wire.