Junction box

[big bab bob]

I am planning to add some surface mount electrical to my 24x22 garage. I have lots of room in my 200A panel

Plans include 1 240V 40Aplug, 2 240 30A plugs and 7 20a plugs on 3 different curcuits. Garage has 4 15a plugs all on the same circuit and a single 240v 30A plug currently. I currently plan to leave to 15a plugs as is. The current single 240V plug will stay but will likely be mover a couple of feet.

What size junction box would I need? Plan is ito install J box surface mount below breaker panel and in through the back of the J box for a cleaner look with the surface mount conduit and boxes for plugs on the walls obviously not all this will be running at the same time it, just a one man show with the wife needes some 120v occasionally.

Initial question is what size J box but does anyone see issues with the above plan? I live in BC Canada, not 100% sure on code here. Home owners can add without permits and I do have a licencesd BIL that can provide some advice but too far away to be much help

 

[sparky 1971]

12X12X4 if you really want a surface mounted J-box under the panel. I've done similar, but used a 12X12X6 box recessed into a 2X4 wall, leaving 2" of box sticking out of the face of the wall which is plenty to get conduit in. If the wall is 2X6, use a 12X12X8. Just make sure the boxes don't have factory knockouts, they won't be in the right spot, drill your own.

 

[wyliesdiesels]

Plans include 1 240V 40Aplug, 2 240 30A plugs and 7 20a plugs on 3 different circuits.

not sure where youre gonna find a 40a receptacle (or plug) as they dont exist. Also plugs go on the end of cords. what you are describing are receptacles.

 

[JohnX14]

Agreed. But 40 amp rated cords with a 50 amp plug are common. The are installed on most ranges, and I'm sure you are aware. This is for others. I put one on Wednesday, before thanksgiving, for a friend/ customer. Not sure what OP is using that is 40A.

 

[big bab bob]

7500 watt heater

I stand corrected on the plug/receptacle issue

 

[wyliesdiesels]

you will need 40a rated wire. receptacle and plug can be 50a. breaker should be 40a

 

[big bab bob]

That was the sort of the plan except I thought I could get a 40A receptacle and plug.

 

[75gmck25]

It depends on the layout of your garage wall storage and fixtures, but long horizontal runs of conduit can get in the way of a lot of storage items.

You might consider mounting that big junction box on the wall above your panel, and then running large diameter conduit around the perimeter of the garage wall at about 8 feet. Everywhere you want a new receptacle (or several) you just install a 4x4 junction box in the conduit and run a drop down the wall to the receptacle.

By US code a wire running around the garage near the ceiling is probably not considered subject to damage, do it does not need to be in conduit for protection. However, it looks neater and allows the use of individual THHN wires if everything is in conduit.

 

[big bab bob]

Next question, steel or plastic boxes/conduit? Does it matter? Which is preferred?

 

[Norcal]

Next question, steel or plastic boxes/conduit? Does it matter? Which is preferred?

Plastic looks DIY, but EMT does take skill to do it correctly/make it look right.

 

[mm08822]

I would do a combination of the previous suggestions:

Mount a metal jbox above the panel semi-flush with the wall surface as Sparky noted.
Install two 2" conduits between jbox and panel in wall.
Jbox mounted at a height that provides no restrictions to equipment/cabinet placement on the walls. 8', 9', etc.....
Conduits can come out both left and right sides.
The furthest conduit runs come out the highest on the jbox (eliminate conduit crossing/saddles later.)
Run emt as it won't sag and needs fewer straps to prevent that. Unistrut not needed, use 1-hole straps with fender washers.
Use 4-11/16 sq boxes on the horizontal conduit runs acting as "T"s. Box fill is important.
Do vertical drops from the 4-11/16 boxes to the recepts at working height. Locate each drop to secure into studs.
Run all thhn/thwn, needed for derating capabilities.
Pull in a drag line for future use.
Use all steel boxes and rounded raised covers.
Put gfci's at each point of use for convenience.(optional & when practical.)

Plan your conduit runs on paper first........Will save you a lot of work and make for a nicer job.

 

[sparky 1971]

I would do a combination of the previous suggestions:

Mount a metal jbox above the panel semi-flush with the wall surface as Sparky noted.
Install two 2" conduits between jbox and panel in wall.
Jbox mounted at a height that provides no restrictions to equipment/cabinet placement on the walls. 8', 9', etc.....
Conduits can come out both left and right sides.
The furthest conduit runs come out the highest on the jbox (eliminate conduit crossing/saddles later.)
Run emt as it won't sag and needs fewer straps to prevent that. Unistrut not needed, use 1-hole straps with fender washers.
Use 4-11/16 sq boxes on the horizontal conduit runs acting as "T"s. Box fill is important.
Do vertical drops from the 4-11/16 boxes to the recepts at working height. Locate each drop to secure into studs.
Run all thhn/thwn, needed for derating capabilities.
Pull in a drag line for future use.
Use all steel boxes and rounded raised covers.
Put gfci's at each point of use for convenience.(optional & when practical.)

Plan your conduit runs on paper first........Will save you a lot of work and make for a nicer job.

All of this plus I want add a couple things. Drill the holes in the jbox before the wall covering goes on. If you wait till the walls are covered you won't be able to get the drill close enough and might wind up having to drill them from inside out. Not that I would have ever made that mistake. And put plenty of hole in it, you can always through knockout fillers in any that don't get used. And I wouldn't bother bringing 1/2" out of the box, use 3/4 for the home runs and 1/2 for the drops.