Wire size to shop

[Aswob5]

I'm leveling off my pad coming up and figured I'd go ahead and run the conduit and water line to the shop while I'm at it. The run is 320' I have a tombstone welder and an air compressor plus the regular lights and outlets. I want to make sure I run big enough conduit but not sure what size wire to account for?

 

[BBob]

You need to decide what your total load will be then size a sub-panel accordingly and then go from there. There are tons of resources and guides to help with figuring out your total load. Once you know your load and a sub-panel size there are again lots of resources with tables to show you what size copper or alu wire you will need and what size conduit will be required.

To add: at 320' for cost alone you'll likely be sizing and using alu conductors.

Here's an example:

200 Amp Wire Size: Service Length & Wiring Gauge Guide

Learn about 200 amp wire size and how to choose the correct wire guage and length for 200 amp service to ensure safe and efficient power distribution.

homeinspectioninsider.com

 

[Johnboy041586]

Yep, gotta figure out you load first. But usually you can get by with 100 amps with 1.25" conduit and #4 awg wire for a normal residential shop. I'd have to check my code book for this scenario though, not sure if you need to up size the wire for voltage drop on a 320' run. Feel free to pm me you specs if you need any more detailed info.

 

[Mighty Mouse]

You could get by with a 50 amp sub panel for what you described, but I would go with a 100 amp to give yourself plenty of capacity to run the welder and compressor simultaneously (plus other stuff).

You're running a long distance. You'll need 2/0 copper or 4/0 aluminum wire to get 100 amps 320' away and meet code for voltage drop. I think 2" conduit would suffice, but you could also consider direct burial cable.

 

[Q child]

You could get by with a 50 amp sub panel for what you described, but I would go with a 100 amp to give yourself plenty of capacity to run the welder and compressor simultaneously (plus other stuff).

You're running a long distance. You'll need 2/0 copper or 4/0 aluminum wire to get 100 amps 320' away and meet code for voltage drop. I think 2" conduit would suffice, but you could also consider direct burial cable.

Mighty Mouse is probably correct. This will cover most typical scenarios. Except I would not direct bury cable because I hate direct buried cable. It is cheap though, so fair enough.
But yeah, it depends on your load. That's a decently long run too, so you might want to upsize.
The code is pretty simple on this, so just calculate your load and select the corresponding wire size and conduit.

 

[HuntHarder]

50amp panel would be undersized... I would do at least a 100 amp panel and if you are running Aluminum, go with 2.5" minimum on the conduit. Our utility mandates minimum 3" for 4/0 triplex service, but you could get by with 2.5"
Keep in mind that direct bury is rated for higher amps, but could be problematic in the long term.

 

[TaperPin]

Running a sub panel to the garage, if there was anything I’d change it would be going up a size in wire. When a big load turns on, LED lights flicker with the sudden minor change in voltage. Drives me nuts. There are probably LED’s designed for this, but going up a size would also fix it.

 

[northernmadman]

Rule of thumb is upsize one size wire for every 100' for voltage drop. Don't forget to pull a bond wire if it's underground conduit. Direct burial cable should have the bond wire integral to the cable.

 

[Johnboy041586]

You could get by with a 50 amp sub panel for what you described, but I would go with a 100 amp to give yourself plenty of capacity to run the welder and compressor simultaneously (plus other stuff).

You're running a long distance. You'll need 2/0 copper or 4/0 aluminum wire to get 100 amps 320' away and meet code for voltage drop. I think 2" conduit would suffice, but you could also consider direct burial cable.

Mighty mouse is correct on the wire size

 

[Mighty Mouse]

50amp panel would be undersized... I would do at least a 100 amp panel and if you are running Aluminum, go with 2.5" minimum on the conduit. Our utility mandates minimum 3" for 4/0 triplex service, but you could get by with 2.5"
Keep in mind that direct bury is rated for higher amps, but could be problematic in the long term.

All good points.

50 amps would be the bare minimum and may result in some breaker trips if using the welder toward the top end of its range. 100 amp would be much better.

2" conduit would be plenty for 2/0 copper, but if he opts for 4/0 aluminum, upsizing the conduit a bit would be wise.

Also agree on direct burial...it's riskier but if the soil isn't rocky and the cable isn't running under a driveway, I would consider it depending on the cost savings vs. conduit.

 

[Beendare]

No way I would direct bury a cable like that.

Here they require sch 80 conduit for that if its considered a secondary service. If it comes from another panel at the house sch 40 is fine. I always recommend doing it to code and taking pics …even if you don’t get it permitted, do per code.

 

[HuntHarder]

What is a bond wire? Its Been about 10 years since I did inside wire work, now I'm on the Utility side. Never heard of a bond wire in conduit here in AZ.

 

[KeithO]

A bond wire is essentially an equipment grounding conductor that you bond your meter can and panel to whatever grounding electrode you go with, cold water pipe, ground rod, or whatever your local municipality require, at the utility disconnect. The biggest thing, besides the conduit and wire size, is that any sub-panel feed needs to be 4-wire, 2 hots, a neutral and a ground.
If you are running it 320' from the source, and you are running PVC and not UF cable, 4/0 AL is the minimum size for a 100 amp service to be safe.

 

[BBob]

A bond wire can also be attached to the rebar in a slab before pouring the concrete.

 

[FAAFO]

Running a sub panel to the garage, if there was anything I’d change it would be going up a size in wire. When a big load turns on, LED lights flicker with the sudden minor change in voltage. Drives me nuts. There are probably LED’s designed for this, but going up a size would also fix it.

 

[FAAFO]

A poor conduit installation underground is worse than direct burial wires in my experience. A whole hell of a lot easier to fix direct burial wire vs conduit also.

do you have the means to pull wire 350’ through a conduit? No way in hell in a resi situation would I pull AL through a pipe. Bigger conduit and it doesn’t pull as smooth as CU. No big deal if you do it for a living but Johnny homeowner will ride the struggle bus.

If it was my home I would do direct bury 1/0 or at most 2/0 URD with the appropriate size ground wire (URD is 3 conductor, two hots and neutral). I would run a number 4 bare copper. You can terminate both ends on a 100A breaker. Good luck trying to land 4/0 etc on a 100A. You can buy the correct crimps but most give the wire a “haircut”. Which is terrible as the electrons flow on outside strands and by cutting them creates heat. no bueno.

Since this sounds like a separate building be sure to terminate in a disconnect. There has to be disconnecting means on most out buildings. Take a few mins and watch a basic bonding/grounding video on YouTube.

Feel free to PM if you have any questions.

 

[CJohnson]

Holy moly there’s some good and bad advice on here.

First, I wouldn’t recommend installing 320’ of conduit without at least one hand hole to pull the wire. Especially if it’s anything other than a straight shot. Personally, I wouldn’t recommend conduit at all due to the cost and the code doesn’t require it unless you’re doing one of the things listed in 300.5. But that’s up to your local code requirements beyond what the NEC may require.

Second, your load will determine your wire size. If you don’t know your load beyond why you’ve listed, I would recommend a minimum of 100a.

Third, there’s several free voltage drop calculators online, but for S&G’s if you install a 100a subpanel at that distance you will need #2/0 copper conductors or #4/0 aluminum conductors. Make sure you pull 2 line conductors, 1 neutral, and an Equipment Grounding Conductor.

Fourth, you don’t need to “bond” anything at your outbuilding. Since you are feeding it from an existing building, it is considered a subpanel. You will need to drive a ground rod and connect it to the equipment grounding bus in the sub panel in the outbuilding. But, don’t bond the neutral and ground in the sub panel.

Fifth, you will need a disconnecting means of some sort on the exterior of the building. That can be a regular disconnect, enclosed circuit breaker, a panel with a main breaker, etc. There’s also some specific labeling requirements.

 

[def90]

No smaller than a 2.5 inch conduit and no more than 4 90 degree bends without a pull box somewhere along the way.

 

[MallardSX2]

I have 4/0 aluminum underground wire and 100 amps service to my garage. I am about 130 feet run to my garage sub-panel. I don't experience any flicker when I weld, or the air compressor kicks on in the garage. I am pretty happy with it.

 

[FAAFO]

I have 4/0 aluminum underground wire and 100 amps service to my garage. I am about 130 feet run to my garage sub-panel. I don't experience any flicker when I weld, or the air compressor kicks on in the garage. I am pretty happy with it.

The 4/0 has nothing to do with flicker but it’s nice to know you’ll be able to go to 200A if you ever want it since it’s double the size you need

Start a little grow and make some side money