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Wire size for sub panel.

Talon2006

Yellow Skull
Joined
May 19, 2020
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So I bought a house, and I need to run power to my garage. 200 amp service at the house and was told I could run a 130 amp sub panel to my garage.

there is a chance I may upgrade my house to 400 amp service someday, and may try to upgrade the garage to a 200 amp sub panel. How big of wire should I run? It is about 100 feet from the house breaker to where the garage would go. I am thinking about 2/0 or 4/0 wire. Is this crazy overkill? Also, what should I expect this to cost? I have not found a reliable price source, and I know of a scrap yard that has rolls upon rolls
kr heavy gauge wire. Hoping to see what they have tomorrow, and hoping sone one can better guide me in.

as far as circuits. I’m planning on running 5 50 amp 220v plugs For my welders, plasma and cnc plasma. I’m thinking I need to source 6 gauge for this, or should I go 4?

I may acquire a cnc mill, and will want to plug it into one of the 220v circuits later, though a phase converter. Should I go 4ga for this or will the 6 gauge be ok? I’m thinking something the size of a VF2.

also, I am thinking about 2-3 120v 20 amp circuits on ea each wall. I’m assuming 10 gauge for this will work.

finally, lights. It seems that amazon LED’s are the shit right now. Should I hardwire then in, or considering most come with a plug anyways should I just run a shit ton of outlets in my ceiling so I can plug them in??

as far as permits, I am in unincorporated county, so I don’t think I need a permit for this.
 
This is irate so be prepared for a bunch of replies saying ‘100’ the VD is gonna run that up to 500 mcm’.

I would do 4/0 al or 2/0 cu for the sub panel. Will be plenty for 130 amps and enough for 200 at 100’ per the *recommend voltage drop if you ever upgrade.

in the shop #6 cu is perfectly fine for 50 amps.

as for price, Home Depot is at 2.25 for 4/0 urd with ground per foot.
 
If you really see yourself upgrading to a 400a (320a) main, run a 2” conduit w/ 3/0 to a 200a main breaker panel in the shop. Feed it from the largest breaker you feel comfortable with at your main. Maybe install a pull box somewhere along the route with a service loop of extra cable in case you need a few-5’ of extra cable when you do your main panel swap.
 
Start by reading this thing called the national electric code..... then maybe your local permit requirements.

Electricity isn't something to fawk with, and if you don't know enough to find out basics like minimum wire size, you probably shouldn't be messing with it....
 
Run a separate 200a main from pole and meter to your new shop. Later when you want to separate utilities for your “business “ it will be much easier.

I was going to post in your other thread but never got around to it.

i have basically exactly what you are looking to do.

24x48’ shop, 8’ ceiling A/C, lathes, mill, welders, plasma table and hoard of useless shit.
 
So you “are thinking” about running this or running that. Like it’s just a feeling you got, a whim, or weird intuition? I think you are on the right path. Go for it man!
 
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Run a separate 200a main from pole and meter to your new shop. Later when you want to separate utilities for your “business “ it will be much easier.

I was going to post in your other thread but never got around to it.

i have basically exactly what you are looking to do.

24x48’ shop, 8’ ceiling A/C, lathes, mill, welders, plasma table and hoard of useless shit.

I really need to give the power company a call.

As far as fitting a mill.... this is a haas VF4. Yes I know everyone things had sucks but they had the easiest to access 3d model.

in the other corner is my cnc plasma I’m building.
 
Perhaps you could replace the panel in the house with a 200 amp feed through and use the panel from the house in the garage? That's how mine is set up, well actually I have a 200 amp feed through panel in my garage and it feeds another panel in the house. It's less than 50'. YMMV
 
Start by reading this thing called the national electric code..... then maybe your local permit requirements.

Electricity isn't something to fawk with, and if you don't know enough to find out basics like minimum wire size, you probably shouldn't be messing with it....

I have come across it the 1000 page version. Is there a good, to the point quick guide?

Its not so much that I don't know how to run a wire load/voltage drop calculator to see what I need for a given load. The question is more, I may upgrade later, should I pull larger cable now, or just do it later "If" I upgrade.
 
I ran 4/0 aluminum to my shop for a 200amp feed, but my distance was a bit less (about 80' I think), and I already had 400 amps at the house with plans to feed my shop later. You'll need 4 conductors, but can get it pretty affordable at big box stores. For your 50 amp circuits, if you run conduit and THHN wire you can use 8 gauge copper. If you use romex, you'll need 6. For 20amp circuits, 12 gauge is what you need, 10 is rated for 30. I'm running a smaller 10hp phase converter for now to power all my 3 phase (including my Fadal CNC), and have it on a 50 amp circuit. I really need to upgrade to a 20hp unit (and obviously bigger wire), but this works fine for me, I just can't push the CNC to its limits and take lighter cuts.

One thing you have to be careful of oversizing wire is if it will fit on the breakers. If you went with 4/0 wire now, you need to make sure that whatever size breaker you use on the house size can accept that wire. A 100amp breaker won't (don't think most 125 will either), so you'd have to splice down to something smaller. It can be done, but adds more work and cost.
 
One thing you have to be careful of oversizing wire is if it will fit on the breakers. If you went with 4/0 wire now, you need to make sure that whatever size breaker you use on the house size can accept that wire. A 100amp breaker won't (don't think most 125 will either), so you'd have to splice down to something smaller. It can be done, but adds more work and cost.

You can get reducers/pigtail adapters for this exact situation.
 
Contact your utility and talk to them about your future service upgrade plans, and see what they will or won’t allow. They will also know if there’s an AHJ that needs to inspect it. We work with 5 different utilities in our area and each one is a little different. Especially when it comes to how they want your service metered. Some of them require the new service to be on a wooden stand, not mounted on the house. A full 400 amps might mean you need a CT cabinet, while some utilities will let you use a 320 amp feed through meter. Also, keep in mind that the NEC is now requiring an outdoor disconnect for homes.

For the shop feed, I’d put in 4/0 aluminum now and the 200A panel. You can always upgrade the feeder end later. It’s a sub panel so you’ll need 4 conductors for a single phase service. They make a 4/0, 4/0, 2/0, 4 aluminum direct burial. I’m not a fan of direct burial depending on soil conditions, but I know there’s plenty of it out there that I installed 25 years ago that’s still fine.
 

Angle that bitch in the corner. You will still be able to get the door open in the rear and it will save a bunch of floor space. I wish I had gotten mine before the shop was full of crap preventing this,
 
Contact your utility and talk to them about your future service upgrade plans, and see what they will or won’t allow. They will also know if there’s an AHJ that needs to inspect it. We work with 5 different utilities in our area and each one is a little different. Especially when it comes to how they want your service metered. Some of them require the new service to be on a wooden stand, not mounted on the house. A full 400 amps might mean you need a CT cabinet, while some utilities will let you use a 320 amp feed through meter. Also, keep in mind that the NEC is now requiring an outdoor disconnect for homes.

For the shop feed, I’d put in 4/0 aluminum now and the 200A panel. You can always upgrade the feeder end later. It’s a sub panel so you’ll need 4 conductors for a single phase service. They make a 4/0, 4/0, 2/0, 4 aluminum direct burial. I’m not a fan of direct burial depending on soil conditions, but I know there’s plenty of it out there that I installed 25 years ago that’s still fine.

If it helps, the PO ran it through the attic, and this seems to be an allowable option. I will only need to do 10" or so underground, which I will put in some type of conduit.


Unless this is a crazy dumb idea.
 
Angle that bitch in the corner. You will still be able to get the door open in the rear and it will save a bunch of floor space. I wish I had gotten mine before the shop was full of crap preventing this,

Damn good idea!
 
95% of the time, people on forums overestimate their garage / shop load.
(yeah i made up the statistic)

when you’re figuring your load keep 2 things in mind.

1. NEC has special sizing for welders and associated circuit wiring due to duty cycle (NEC 630.11 & NEC 630.12)

2. You can’t run everything at once. You won’t be welding with the dial cranked up to the max, while simeoultaniosly grinding on your big grinder, and plasma cutting, etc.
 
Perhaps you could replace the panel in the house with a 200 amp feed through and use the panel from the house in the garage? That's how mine is set up, well actually I have a 200 amp feed through panel in my garage and it feeds another panel in the house. It's less than 50'. YMMV

This is what I did at my place. Feed through 200 amp panel at the pole where the meter is. House is on a 100amp breaker and the shop gets the feed through and has it's own 200 amp panel.

I would do more than you need now.. instead of wishing later..

its also good if you are gonna run a bunch of cords for xmas lighing.. but I dont go extreme with lights anymore..

Do you ever just shut the fuck up about things you know nothing about?
 
I just had a subpanel installed outside. Technically an RV panel but I’m using it for welding and possibly purchasing a hybrid car to charge.

Electrician fed with 6 AWG. Approximately a 50ft run
It was about $700 buried within the rest of the work ol we did. I suspect he brought left over wire from another job. 60 amp breaker in the panel.

Outside I have the following:

240v 50 amp 4 prong RV
120v 30 amp 3 prong RV
120v 20 amp GFI

I think I could run a hot tub off my set up in the future
 
95% of the time, people on forums overestimate their garage / shop load.
(yeah i made up the statistic)

when you’re figuring your load keep 2 things in mind.

1. NEC has special sizing for welders and associated circuit wiring due to duty cycle (NEC 630.11 & NEC 630.12)

2. You can’t run everything at once. You won’t be welding with the dial cranked up to the max, while simeoultaniosly grinding on your big grinder, and plasma cutting, etc.

this
I've been reasonably happy with 2ga alu on a 100' run

even my big tig welder that supposedly draws 104a on the dataplate hasn't actually tripped the 60a breaker it is on, and I've run that thing hard enough that the cup was glowing halfway back up to the watercooled torch

if you're gonna have a/c and electric heat, and RV outlets and multiple people in the shop, by all means get you some 500mcm, if not two of them
 
Going back and reading this again, if you really think you are going to run a CNC mill equivalent to a VF2 off this garage panel, you’re going to need it to be 200a+. The single phase circuit for the mill alone will probably be 125a-150a. Then you’re going to need air to support it. And lights. And while the machine is in a long cycle part, you may want to do a bit of spray transfer on that tractor you need to fix...

135a is not going to feed a shop with a legit CNC machine.
 
Call your power provider and see if you can get a seperate service for your shop, and how big.
 
Going back and reading this again, if you really think you are going to run a CNC mill equivalent to a VF2 off this garage panel, you’re going to need it to be 200a+. The single phase circuit for the mill alone will probably be 125a-150a. Then you’re going to need air to support it. And lights. And while the machine is in a long cycle part, you may want to do a bit of spray transfer on that tractor you need to fix...

135a is not going to feed a shop with a legit CNC machine.

^ All of that. Plus, 135A is a special order breaker. Panels are rated 100, 125, 150, 200, 225, etc. Don’t go smaller than 200.
 
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I read something on the old site about my delimma. Basically they were saying run the 2-2-2-4 copper wire, and if you wanted to upgrade later you could run a second line.
im not sure if they where meaning a second sub panel, or somehow running a parallel wire to the same panel. Either way it sounded sketchy and am thinking it’s a “getto” fab solution.


Yesterday I called the power company, 400 amp service is an option, as long as I have an electrician set up everything on my end. I have no idea what that involves and couldn’t get ahold of an electrician to get a quote.

I also went by the scrap yard and found 2/0 SER cable, and 2awg ser cable for a great price. Not sure what direction I want to go with. The 2/0 I feel I indicated to be able to pull, the 2awg would be manageable imho as far as physically pulling/routing it.
 
Just run aluminum 2/2/2/4 urd in conduit (at least 2", size it for 4/0-4/0-4/0-2) around here it's $1.40ish a foot for that wire.
Down the road if you want to upgrade, pull it out, pull in 4/0-4/0-4/0-2 and sell the 2/2/2/4 on Craigslist for $80.


Aaron Z
 
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