Running a sub panel to the garage/shop

[Don1357]

I'm starting to figure out how to wire my garage/woodworking shop. I'm posting this in hopes that it may save me from painting myself into a corner. So far I'm thinking a 70-amp sub panel ought to do it (max amps for #4 copper wire).

I don't see me running anything bigger than a 3hp motor. Heck the Unisaw currently has the original 1.5hp and if that dies I may bump it to a 2hp. A lot of the machines I don't have yet so I can only make educated guesses. The Delta dust collector pushes 3/4hp but may eventually be upgraded to something hitting 2hp. A planer would be sub 3hp, probably wired on the same circuit as the table saw so both won't run at the same time (as in go ahead, try, watch it trip the circuit. Better your shared circuit than the main one). Joiner, band saw, lathe, routers, etc ad nausea, all collectively draw a lot of power but this is my shop, not many machines will be working at the same time. I figure baseline dust collector, lights, (compressor kicking in), a few amps for radio, and the bulk for machines that largely will take turns on the power meter.

Basically I'm willing to live with having to be judicious on how I use power (like turning the table saw and the planer being a no-no else it trips the breaker). But of course within reason...

 

[loganb]

My 2 cents

Put in at least a 20 slot main breaker panel(kind with a main breaker vs a main lug) so you can easily kill power to the panel. Most garage shops will benefit more from the additional circuits than from the additional amps. I just picked up a 32 slot main breaker panel, same brand as the house panel for simplicity for under 75 bucks(was on sale but normal was still under 100)

Running 2-2-2-4 AL service feeder wire for me is about 1/3rd the cost of copper and is good for 90 or 95 amps, may not be available at the Lowes or Depot though so may need to go to a electric supply shop to get





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[theoldwizard1]

60A @ 240V is quite common.

Running 2-2-2-4 AL service feeder wire for me is about 1/3rd the cost of copper and is good for 90 or 95 amps, ...

Mobile Home Feeder (MHF) cable. Cut to length.

 

[shamus29]

The shop I work at has a large welder and large compressor and all Rowe have servicing it is 40 amps and we’ve never tripped the main breaker. Like posted earlier more circuits will be more beneficial than more amperage. The welder and compressor are never ran at the same time. I’m in the process of building building a garage for myself and my cousin that’s an electrician he’s said you’d be crazy to run anything more then 40amps out there so he suggested #6 aluminum tec cable for direct burial.


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[Bolson32]

Running 2-2-2-4 AL service feeder wire for me is about 1/3rd the cost of copper and is good for 90 or 95 amps, may not be available at the Lowes or Depot though so may need to go to a electric supply shop to get

Menards sells MHF by the foot as well. OP is in AK so I'm not sure if they're down there or not. But I'm pretty sure HD and Lowes sell that as well.

 

[loganb]

60A @ 240V is quite common.



Mobile Home Feeder (MHF) cable. Cut to length.

For my local Menard, SE-R is around 10 cents/ft cheaper than MHF for the same size but both are stocked locally for sales by the foot. The local HD or Lowes don't generally have any stock of service wire so when its time to Menards I shall go!

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[pattenp]

...... I’m in the process of building building a garage for myself and my cousin that’s an electrician he’s said you’d be crazy to run anything more then 40amps out there so he suggested #6 aluminum tec cable for direct burial.


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Well there are alot of crazy people that need more than 40A.

 

[Don1357]

My 2 cents

Put in at least a 20 slot main breaker panel(kind with a main breaker vs a main lug) so you can easily kill power to the panel. Most garage shops will benefit more from the additional circuits than from the additional amps.

I figure as much. Wiring a bunch of circuits as 220v would eat up a bunch of my slots.

Running 2-2-2-4 AL service feeder wire for me is about 1/3rd the cost of copper and is good for 90 or 95 amps, may not be available at the Lowes or Depot though so may need to go to a electric supply shop to get

I'll research this. Thanks.

 

[Bolson32]

For my local Menard, SE-R is around 10 cents/ft cheaper than MHF for the same size but both are stocked locally for sales by the foot. The local HD or Lowes don't generally have any stock of service wire so when its time to Menards I shall go!

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Noticed that as well, but you can't direct bury SE-R. OP didn't state whether he was putting it in conduit or direct burying it. I don't plan on running conduit for 180ft when I do it so it's getting direct buried.

 

[pattenp]

SER is not to be used underground, not even if put in conduit.

 

[Don1357]

Other than driers and the like that may internally run both 220v and 110v, is there much need for a four pole circuit?

 

[pattenp]

Other than driers and the like that may internally run both 220v and 110v, is there much need for a four pole circuit?

What am I missing? What is a four pole circuit? I guess you are talking about a 4 conductor circuit.

 

[loganb]

Other than driers and the like that may internally run both 220v and 110v, is there much need for a four pole circuit?

When you say 4 pole circuit do you mean pulling 4 wires from the main panel to this sub-panel vs pulling 3 wires and having neutral and ground be common? If so that wouldn't be allowed per code. Once you're past the first disconnect from the power company, neutral and ground aren't allowed to be bonded together so you have to pull 4 wires to my knowledge to any sub-panels and remove any bonding screws in the panel that may join the neutral bar to the ground bar

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[Don1357]

What am I missing? What is a four pole circuit? I guess you are talking about a 4 conductor circuit.

Yes, sorry, messing up the terminology.

4 conductor vs. 3 conductor. Is there a point having the extra wire just in case? My understanding is that driers and other appliances that internally run both 220v and 110 need the extra neutral (white) for the 110v circuit. I can't think of a machine that would require this but I figure I would ask, in case this has come up for somebody else.

 

[pattenp]

Yes, sorry, messing up the terminology.

4 conductor vs. 3 conductor. Is there a point having the extra wire just in case? My understanding is that driers and other appliances that internally run both 220v and 110 need the extra neutral (white) for the 110v circuit. I can't think of a machine that would require this but I figure I would ask, in case this has come up for somebody else.

If you want 120V/240V available then you have to run 4 conductors as the feeder to the subpanel. Whether you have any 4 wire circuits to outlets off that subpanel is strictly based on ones need, which in most cases is unlikely. If you only wanted 120V then 3 conductor feed is all you need. The neutral is needed to have 120V , the extra conductor you are talking about is the second hot to have 240V.

 

[spudley]

OP, is this a detached shop?

 

[Yankeefarmer]

Noticed that as well, but you can't direct bury SE-R. OP didn't state whether he was putting it in conduit or direct burying it. I don't plan on running conduit for 180ft when I do it so it's getting direct buried.

I just finished running 140’ of 2” conduit in our rocky New England ground. Neighbor friend electrician recommended I direct bury, but buying sand fill to protect against our rocks would have been twice the cost of the conduit. I don’t regret my choice one bit; placing the conduit and pulling the cable were far less work and time consuming than digging the trench, smoothing the bottom, and properly backfilling. There were 3 spots where I had to hammer/chip away a couple inches of rock to get to code depth. I would have had to do more of that for the deeper depth required for direct bury.After my experience, I wouldn’t think twice before going the conduit route. Of course, your soil conditions may be more favorable than mine.

 

[Don1357]

If you want 120V/240V available then you have to run 4 conductors as the feeder to the subpanel. Whether you have any 4 wire circuits to outlets off that subpanel is strictly based on ones need, which in most cases is unlikely. If you only wanted 120V then 3 conductor feed is all you need. The neutral is needed to have 120V , the extra conductor you are talking about is the second hot to have 240V.

I'm specifically talking about the outlets coming out of the sub panel, Specifically pondering if I'll ever need a 4 conductor wire for any of them. I'm pretty sure the answer for garage and woodworking machines alike is 'unlikely', but I figure I would ask anyways in case somebody has seen a case.

 

[pattenp]

I've seen people use old stoves for powder coating that need the 4 wire outlet for 120/240V, other than that not so much.

 

[loganb]

Unless you get some late model equipment with lots of electronic whistles(like a cnc), decide to put in an RV outlet or a generator plug you probably won't need the 4 wire outlet. Not sure if you're planning on wiring in conduit or in romex behind finished walls...but the benefit of conduit is that if you need 4 wire its easy to add

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[Bolson32]

I just finished running 140’ of 2” conduit in our rocky New England ground. Neighbor friend electrician recommended I direct bury, but buying sand fill to protect against our rocks would have been twice the cost of the conduit. I don’t regret my choice one bit; placing the conduit and pulling the cable were far less work and time consuming than digging the trench, smoothing the bottom, and properly backfilling. There were 3 spots where I had to hammer/chip away a couple inches of rock to get to code depth. I would have had to do more of that for the deeper depth required for direct bury.After my experience, I wouldn’t think twice before going the conduit route. Of course, your soil conditions may be more favorable than mine.

What are the differences between conduit and direct bury depths? Few inches or are we talking feet?

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[pattenp]

NEC is 24" for direct bury, 18" for PVC conduit.

 

[Don1357]

What are the differences between conduit and direct bury depths? Few inches or are we talking feet?

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Depending on what you use is how deep you have to go, from six inches to 2 feet. Usually how far you have to go and how nasty the digging is determines what you go with.

Funny story: I have a sauna. I happened to be digging around where the piece of conduit goes into the ground next to the house wall. Imagine my surprise when I found out that the conduit only went like 3 inches underground and the rest is two strands of burried cable... I should do something about that...

 

[shamus29]

Depending on what you use is how deep you have to go, from six inches to 2 feet. Usually how far you have to go and how nasty the digging is determines what you go with.

Funny story: I have a sauna. I happened to be digging around where the piece of conduit goes into the ground next to the house wall. Imagine my surprise when I found out that the conduit only went like 3 inches underground and the rest is two strands of burried cable... I should do something about that...

Here in Canada you have to go 3 feet down with 3inches of sand on top and bottom weather your in conduit or not


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[gtae07]

I've seen people use old stoves for powder coating that need the 4 wire outlet for 120/240V, other than that not so much.

I had our old stove out in the shop for a while to bake paint on to parts. Having the correct outlet for that was useful. I have a pigtail/adapter for the welder and plasma cutter.

I overestimated the wire I needed, so when I had the garage wall open (the main panel is there) I added another 240V outlet there in case I ever needed to weld up there or if we ever got an electric car.

 

[csp]

4 conductor vs. 3 conductor. Is there a point having the extra wire just in case?

The point has nothing to do with equipment needs, it's code. In a subpanel the neutral and ground must be isolated from each other.

 

[Don1357]

The point has nothing to do with equipment needs, it's code. In a subpanel the neutral and ground must be isolated from each other.

That question was not about the sub panel but about circuit wiring. How some 240 circuits require the extra wire and how while I can't think of anything I'll be running needing it, whether it makes sense to wire with the extra cable just in case. Again, extra cable meaning to the outlets.

 

[theoldwizard1]

For my local Menard, SE-R is around 10 cents/ft cheaper than MHF for the same size but both are stocked locally for sales by the foot. The local HD or Lowes don't generally have any stock of service wire so when its time to Menards I shall go!

Make sure it is spec'd for underground installation. Cable must be rated for underground/wet even if it is inside of a conduit.

 

[mike93lx]

There is basically nothing in a shop that will require a 4 wire circuit.

Welders, lifts, table saw, band saws, planers, dust collectors, compressors... All are a 3wire circuit

 

[Don1357]

There is basically nothing in a shop that will require a 4 wire circuit.

Welders, lifts, table saw, band saws, planers, dust collectors, compressors... All are a 3wire circuit

That's what I thought. I'm old enough that I don't mind asking stupid questions just to make sure

 

[sparky 1971]

I have installed four wire receptacles in a few shops, but not for "shop" equipment. A couple dryer receptacles and several 14-50R's. All but one of the 14-50's were for campers, but the other was for an old range. The wife liked to do canning in the fall, but it made the house too hot and stinky so she invaded the man cave and had her own corner for a couple of weeks a year.

 

[csp]

That question was not about the sub panel but about circuit wiring. How some 240 circuits require the extra wire and how while I can't think of anything I'll be running needing it, whether it makes sense to wire with the extra cable just in case. Again, extra cable meaning to the outlets.

Oh, gotcha. Every reply previous to that question was about feeder wire to the subpanel so I didn't catch the change in subject.

As others have said, nothing in the shop will be like a dryer to need a separate ground and neutral.

 

[Don1357]

The 240v 60-gallon air compressor came with a four prong round locking type plug. On the compressor the white cable is just not wired to anything.

If I put a four prong outlet, does code demands it to be a four wire cable with ground wired from outlet to breaker, or can I wire it as a 3-wire outlet? Obviously I know what it is and what I'm plugging in but I don't want to unnecessarily violate code.

 

[Don1357]

While I'm asking... The motor is rated as 17.3 amps @ 230v. Wiring this with 12/2 to a 20 amp 240v breaker should be satisfactory? The cable distance from the breaker box should be about 30 feet. I don't know if it would benefit from wiring with 10/2, I just came back from Lowes and I know my wallet would benefit if I wire with the 12/2 I have on hand...

 

[mike93lx]

What is the HP rating? The plug probably isn't code (assuming it is 3hp or greater). 12/2 will likely be too small

 

[Don1357]

What is the HP rating? The plug probably isn't code (assuming it is 3hp or greater). 12/2 will likely be too small

It claims to be a7HP motor which would be impossible with the motor rated at 17.3 amps, so most likely it is 7hp peak but in reality a 5hp motor.

 

[mike93lx]

It claims to be a7HP motor which would be impossible with the motor rated at 17.3 amps, so most likely it is 7hp peak but in reality a 5hp motor.

The NEC sizes circuits based on the motor nameplate. Can you post a picture?

 

[Don1357]

See attached

 

[mike93lx]

Thanks. You size the circuit since it is "spl" rated. 17.3amps x 1.25 = 21.63a. So that means either 10/2 nm-b or 12 thhn in conduit

A 60 gal comp isn't portable. I would lose the plug and wire it into an inexpensive a/C disconnect.

It needs a 30a breaker

 

[Don1357]

Thanks. You size the circuit since it is "spl" rated. 17.3amps x 1.25 = 21.63a. So that means either 10/2 nm-b or 12 thhn in conduit

A 60 gal comp isn't portable. I would lose the plug and wire it into an inexpensive a/C disconnect.

It needs a 30a breaker

Sweet baby Jesus! $72 for 50 feet of 10/2 wire... On top of that the only plug they had in 30amp/240v was the turnlock so that was $20 for the plug and $20 for the outlet...

What does the SPL means?