Sub panel to workshop

[rbragg]

I am wanting to run a 100 amp sub panel to my workshop from my house that’s has a 200amp panel. The run is going to be 150-200 ft depending on the route I take. I have been reading and know I will have a voltage drop. I plan on running...

6.5 HP air compressor

Arc and Wire welders

Plasma cutter

All are 240....

As well as various other wood working things and hand tools. Obviously not all at once but the Plasma and compressor might run together.

Any in-site as to the size of wire I would need to run? Would I be ok running aluminum or should I scratch that idea and run copper? Also will I need multiple grounding rods at the workshop? I have read some conflicting things. Thanks.

 

[Tooldeals?]

100A should be fine for the garage. To give you a quick answer on sizing, download a wire size calculator. They are not always perfect but will put you in right direction. Shoot for 3% or less voltage drop.

Aluminum vs copper doesnt matter. Personal preference. Aluminum is cheaper/ lighter but bulkier
Copper is more expensive/ heavier but smaller diameter wire.
Grounding requirements are likely something you need to reference at a local level.

Word of advice- When you do this, add an extra pipe or two for future use. (Ethernet, cable, 3 way light switches, ect)

 

[OptionalStop]

I have about the same length run and installed a 100 amp subpanel with 2-2-2-4 aluminum wire. I have my breaker in the house at 90 amps since that's the max you can pull with 2 gauge wire. In my 24 x 36 shop I put quad 120v boxes and a 240v box at every post, each on its own circuit. It's overkill, but I just want to do it once and be done with it. Now I can move around my big 240v equipment and always have somewhere to plug them in.

 

[pattenp]

Using 200ft as the distance, if you want a full 100A capacity you will need to use at least #1/0Al. One suggestion is to use 2/0-2/0-2/0-1 MHF for direct bury, but putting in conduit is the better choice. If using conduit, I'd use the same size conductors in XHHW-2 (less bulky). The MHF in 2-2-2-4 is good for a max load of 60A at 200ft to keep the VD at 3%.

Edit: The 2/0 MHF would be best in 2.5" conduit whereas the 2/0 XHHW-2 can get by in 2" conduit.

 

[rbragg]

Thanks for the reply’s. I wasn’t too far off on my thinking.

 

[wyliesdiesels]

I am wanting to run a 100 amp sub panel to my workshop from my house that’s has a 200amp panel. The run is going to be 150-200 ft depending on the route I take. I have been reading and know I will have a voltage drop. I plan on running...

6.5 HP air compressor

Arc and Wire welders

Plasma cutter

All are 240....

As well as various other wood working things and hand tools. Obviously not all at once but the Plasma and compressor might run together.

Any in-site as to the size of wire I would need to run? Would I be ok running aluminum or should I scratch that idea and run copper? Also will I need multiple grounding rods at the workshop? I have read some conflicting things. Thanks.

the equation for the voltage drop calcs is posted on the electrical FAQs thread.

Not doing the math(in a hurry) I'd imagine you could get by with 2/0 AL. you will need 4 wires, subpanel needs an isolated neutral bar and yes you will need 2 grounding electrodes.

Where are you getting conflicting info?

100A should be fine for the garage. To give you a quick answer on sizing, download a wire size calculator. They are not always perfect but will put you in right direction. Shoot for 3% or less voltage drop.

Aluminum vs copper doesnt matter. Personal preference. Aluminum is cheaper/ lighter but bulkier
Copper is more expensive/ heavier but smaller diameter wire.
Grounding requirements are likely something you need to reference at a local level.

Word of advice- When you do this, add an extra pipe or two for future use. (Ethernet, cable, 3 way light switches, ect)

why would he need to reference grounding requirements on the local level? The NEC is very clear on the requirements and theres not really any reason to differ on it.

 

[rbragg]

I was getting “conflicting info” from a neighbor that did essentially the same thing. He paid someone but I am wondering if everything he did was right because he only has one grounding rod.

Yes 2/0 is correct I downloaded the app. I can either run 2/0 or #1 copper. I would like to do aluminum and save some $$$ but hearing that the wire can expand and retract over time and cause a fire kind of scares me a bit.

 

[ford33]

Nobody has mentioned that you should calculate the actual power you need. A one person shop may not need 100 or 90 amps of power. You will spend much more money unnecessarily on larger wire at 200 feet than is necessary if you only need 60 amps. The cost savings is significant.

Another vote for a second conduit in the ground for something in the future.

 

[Natty Bumppo]

I just wired my garage this past summer and had a very similar situation in regards to your tool demand. I only had to go 100 feet. I'm a one man shop. I used 2-2-2-4 aluminum in conduit, a 100 amp sub panel on a 90 amp beaker from the house, and two 8' ground rods 6' apart.

 

[jim111]

[/GD] I would like to do aluminum and save some $$$ but hearing that the wire can expand and retract over time and cause a fire kind of scares me a bit.[/QUOTE]

Properly installed aluminum feeder cable is perfectly safe

 

[pattenp]

The new aluminum wire alloy does not have the issues of aluminum wire of the 70's.

 

[rbragg]

Nobody has mentioned that you should calculate the actual power you need. A one person shop may not need 100 or 90 amps of power. You will spend much more money unnecessarily on larger wire at 200 feet than is necessary if you only need 60 amps. The cost savings is significant.

Another vote for a second conduit in the ground for something in the future.

Unless I’m off I have a 7.5 HP 80 gallon compressor and it should use 35-40.

My plasma cutter I have been told will use 40-50 amps depending on what I’m cutting.

Lights will be LED so probably not much. 4amps.

And chargers etc plugged in while doing other things is minimal I would assume.

The plasma and compressor would be the only things running at once. But that’s still 80-90 if my info is good and correct (I’m not saying it is)

 

[wyliesdiesels]

The new aluminum wire alloy does not have the issues of aluminum wire of the 70's.

I was getting “conflicting info” from a neighbor that did essentially the same thing. He paid someone but I am wondering if everything he did was right because he only has one grounding rod.

Yes 2/0 is correct I downloaded the app. I can either run 2/0 or #1 copper. I would like to do aluminum and save some $$$ but hearing that the wire can expand and retract over time and cause a fire kind of scares me a bit.

As pattenp said, the aluminum wire of today is not the same as decades ago

heres an article

http://www.southwireblog.com/copper...shed-reputation-story-aluminum-building-wire/

 

[Norcal]

The new aluminum wire alloy does not have the issues of aluminum wire of the 70's.

The early 1970’s is the time it went from aluminum to aluminum alloy to correct the issues.

 

[rbragg]

Once again thanks for the info. Got a quote yesterday for materials and etc and will be using the 2/0 aluminum it will cover me for 150 or 200 depending on how I end up having to route it. If I knew 150 would be Max I could have gotten away with the 1/0 but the price wasn’t much more.