Check my conduit wiring for adding 240v circuits

[StevenMorgan]

I've recently moved houses and have a new to-me garage to get settled into. It is a drywall finished 3-car garage in a new construction residential neighborhood. There is a 200A panel with room for two 240v circuits to be added before being maxed out, and I need to hook up my 10hp 1ph air compressor and set up a NEMA 6-50R welding receptacle.

The most logical layout for placing the compressor and welder is on the opposite corner of the garage. A rough estimate says it will be 55' or so away, but within line of sight. I assume the fastest and easiest way to do this is with a single conduit for both circuits.

My pertinent compressor specs are listed here: https://www.garagejournal.com/forum/showthread.php?t=309088

I'm thinking 1" PVC conduit from the panel to the other corner of the garage, with a 60a safety disconnect serving as the junction box for the compressor hookup. I'll pull five #6 THHN wires (2 red, 2 black, and 1 green) through the conduit, and add the 6-50R receptacle for my TIG welder directly below the safety disconnect.

Does that sound correct?

 

[sberry]

Use 3/4 steel pipe and run a circuit thru each one. You can use all black, doesn't need red and the green could be a 10 but I might go to 8 as it depends on the breaker size for the comp,,, and possibly for the welder depending on model.

 

[PCustoms]

10hp 1ph motor?

Most POCO restrict anything that size, you'll dim the lights in the neighborhood when you turn it on!

 

[wyliesdiesels]

10HP air compressor.

Damn what are you doing that requires that beast?

You should check with your PoCo before firing that thing up.

You may be limited to 5 or 7.5HP...

 

[nelstomlinson]

I don't have a code book handy, so this is from memory. I think that PVC isn't intended for use inside a building like that, but I used it in my shop. EMT doesn't cost much more, and really isn't much harder to run, especially if you use factory 90s.

You need to look in the fill tables in the code book for the conduit type you are using. Choose your wire, then see what size conduit you need. If your conduit is a little tight, pulling gets a lot harder, so don't go small.

I think I recall that a 50A breaker needs #6 wire. Look in the NEC tables for the required equipment grounding conductor size. I don't remember what you need. I think the tables you need for this are in Section 250? In any event, it's probably going to be cheaper to get a single spool of #6 and use it for all of the conductors.

If you take sberry's advice and use all black wires, tape both ends of one of them white for a neutral, tape both ends of one of them red for your other hot, and tape both ends of one of them green for ground, before you pull the wires. It's easy to identify before the pull, and much harder to figure out what is what after the pull.

Finally, if your walls aren't finished, run some 3 conductor with ground #6 NM (the generic term for Romex) in the walls.

Edited to add: A fill table I found online suggests for EMT you can use 4 #6THHN in 3/4" and 7 #6THHN in 1". I would go with 1" for sure.

 

[brewchief]

With only a couple of open breaker spaces I might consider running larger wire and using a subpanel by the compressor instead of a disconnect.

How much power does your welder pull and do you ever need to weld when the compressor could be running? Do you ever see yourself running a plasma cutter that will need the compressor running at the same time?

 

[sberry]

I believe it's got to be green. The other 2 can be black. They are interchangable on single phase in this app. I believe the rule is remarking 6 or smaller.
I am a fan of using 3/4 where I can, it's so much simpler and having single circuit in pipe for large dedicated equipment is hard to beat. It allows the breaker to be tailored and allows the wire to be used for larger machines if needed. You may not even need 6 for the welder depending on the model, also depends if it comes factory wired plug and cord.
Anyway, 3/4 is so standard, the run is a little long so there is something to be said for running a single pipe but it's not all that big a deal to run extra pipe either and no jboxes needed, got single circuit right to the welder recept. Uses common 4x4 box with off the shelf covers.
Use deep boxes. The recept won't go in a shallow one. I like a raised cover. It's simple and keep in in stock, you can always use a 4 inch box for other apps.

 

[sberry]

I believe it's got to be green. The other 2 can be black. They are interchangable on single phase in this app. I believe the rule is remarking 6 or smaller.
I am a fan of using 3/4 where I can, it's so much simpler and having single circuit in pipe for large dedicated equipment is hard to beat. It allows the breaker to be tailored and allows the wire to be used for larger machines if needed. You may not even need 6 for the welder depending on the model, also depends if it comes factory wired plug and cord.

 

[alfredeneuman]

"I need to hook up my 10hp 1ph air compressor"

A 10hp 1Ø motor draws, by the NEC, 50 amps.
50 X 1.25 (the multiplier for motors) = 62.5 amps
The disconnect must be horsepower rated, not amp rated. At any rate the 60 is no good.
The disconnect is required to be within 50' & within sight of the motor location.

You can't use the disconnect as a junction box

 

[wyliesdiesels]

I don't have a code book handy, so this is from memory. I think that PVC isn't intended for use inside a building like that, but I used it in my shop. EMT doesn't cost much more, and really isn't much harder to run, especially if you use factory 90s.

You need to look in the fill tables in the code book for the conduit type you are using. Choose your wire, then see what size conduit you need. If your conduit is a little tight, pulling gets a lot harder, so don't go small.

I think I recall that a 50A breaker needs #6 wire. Look in the NEC tables for the required equipment grounding conductor size. I don't remember what you need. I think the tables you need for this are in Section 250? In any event, it's probably going to be cheaper to get a single spool of #6 and use it for all of the conductors.

If you take sberry's advice and use all black wires, tape both ends of one of them white for a neutral, tape both ends of one of them red for your other hot, and tape both ends of one of them green for ground, before you pull the wires. It's easy to identify before the pull, and much harder to figure out what is what after the pull.

Finally, if your walls aren't finished, run some 3 conductor with ground #6 NM (the generic term for Romex) in the walls.

Edited to add: A fill table I found online suggests for EMT you can use 4 #6THHN in 3/4" and 7 #6THHN in 1". I would go with 1" for sure.

No prohibition against PVC inside.

#6 and smaller CANNOT be phase taped.

And #8 THWN has a 50a ampacity.

 

[StevenMorgan]

Hmmmm... a lot of responses. Let me try and answer some questions.

The welder is a Lincoln TIG 185 machine. Maybe 35a max load. I just figured I’d run the welder circuit as if I have something pulling the actual 50a of the breaker and receptacle...?

The compressor is a beast for sure that I use for my blast cabinet and DA sanders. It’s nice to have your compressor catch up to you, kick off and wait about 10min before cycling while you’re continuously blasting in the cabinet. At the old house it was 28’ wiring run length within line of sight on a 70a beaker, no disconnect needed. #6 THHN wiring in 3/4” pvc conduit. The motor pulls 38a at 1.00SF and worked perfectly at the old house.

I guess I will need to measure the wiring run exactly to see if I can eliminate the disconnect.

 

[sberry]

The rules are for good reason. But,,,, wouldn't lose sleep over 5 ft in my own place provided it was in clear sight etc. As you will be told, the motor circuits are HP rated but again it wouldn't personally cause me a great concern with the 6 on a 38A motor. Do you have a pic of the tag? That is really a 7.5 up unit regardless of what the label says.
They have labeled some "specials" I believe to get around this (wait for another opinion before accepting this as gospel). I am not sure they anticipated modern advertising and number stretching when they wrote the code.

 

[StevenMorgan]

It’s a real 10hp Baldor motor.

 

[wyliesdiesels]

The rules are for good reason. But,,,, wouldn't lose sleep over 5 ft in my own place provided it was in clear sight etc. As you will be told, the motor circuits are HP rated but again it wouldn't personally cause me a great concern with the 6 on a 38A motor. Do you have a pic of the tag? That is really a 7.5 up unit regardless of what the label says.
They have labeled some "specials" I believe to get around this (wait for another opinion before accepting this as gospel). I am not sure they anticipated modern advertising and number stretching when they wrote the code.

#6 is too small for a 10HP motor.

Wiring is sized by HP not FLA on nameplate

It’s a real 10hp Baldor motor.

You need 62a rated wire as pointed out above.

 

[sberry]

My 5 is 22 I think. It's in a machine, pressure washer. Heavy duty Baldor and including the rest of the machine comes factory 10 cord and 30 end.
I have a Leeson 3 and it's load is 18 on a comp. A well rated 3 but it's 14 as I recall and anothe Marathon on a comp pulls 26, dont remember exact what the HP is.

 

[sberry]

I temember one on here, a 7 1/2 where the guy had the "electrician" from work wire it up with a 12 cable, worked for 18 years,, , ha. The son came here for something, maybe to move it, and it didn't look right and asked, was sposed to have a 6 wire.

 

[alfredeneuman]

#6 is too small for a 10HP motor.

#6 in the 75° column is 65 Amps

 

[sberry]

I didn't look at the chart but I thunked it might be good sized for motors.

 

[exranger06]

You can't use the disconnect as a junction box

Says who?

 

[alfredeneuman]

Says who?

According to 312.8 it CAN be used, as long as there is adequate space provided.
The same applies with panels. It must be labelled as such though.

 

[sberry]

If I was going to run a big pipe and short on breaker spaces would run a 8 space main lug, if I was going to feed it with 2 circuits would run 2 pipes, wouldn't fukk with jboxes, would run one to each appliance. Especially in a home/resi type garage, no mistaking what goes where.
I have ran a lot of welder circuits, never needed to "run or add something with a full 50A" later, some other equipment. There are several reasons for this, I know there is a compulsion on here to "future proof" but what it really does is simply park some wire a guy never uses.
Been there, done this, did it more than once and found out I used way less than I ever thought I would. None of the additions really ended up in the same spot and never needed shate I thought I might. Its just as easy and more practical to cross some bridges if you come to them instead of investing for every "what if" scenario often decades ahead. The 50 outlet you install for a welder isn't motor rated for 5 hp anyway and its not correct for most ovens, what would a guy ever put there?
The NEC is very keen about some things they allow, they really understand adequate. Just because it the minimum doesn't mean its undersized and is slightly different than NEMA type standards within equipment that are often pushed to the top end of the allowable ranges etc.
This is often obvious in other posts,,, I only use a 6 or an 8 for welding etc when they are plugging a machine that comes with a 14 cord. Some of the single voltage 240 units come 12,,, only require a 14 for 75 ft. The only reason it has a 12 on it is that its the same one they use on other machines and it allows it to be plugged in to 50A circuits.

 

[sberry]

A lot of this may depend on wire I already had, how much I had to buy, if I needed the left over for other jobs etc. and the real demands of the machine. If it needs 6 then it needs 6 but if its in its own pipe might use 10 for the welder if I had it,,, if I had to buy it special and really if it ever did come to a situation for higher demand,, very unlikely in a separate pipe is only a small chore to tug a new wire thru and the exact length will be known.

 

[wyliesdiesels]

#6 in the 75° column is 65 Amps

Yeah whoops was thinking of #6 NM