Supply for sub panel

[hoylebros]

Hey guys. Just brainstorming here. We'll be having our detached shop put up within the next month. I'm sure this has been asked a million times, but...here goes. I plan to have a 100amp sub panel ran to the shop from the main house panel which is 200amps. The run is going to be 90-100'. I'm also wanting to direct bury the cable. What size wire should be used? I've used some calculators online and have an idea, but just curious what you guys have to say. If I need to provide any other info let me know. Thanks!

 

[Rickster55]

I think a Christmas tree light extension cord should be fine! JK, of course! We have some really helpful guys here who will hook you up with the proper way soon. Welcome to GJ!

 

[Flexia]

Use. 2/2/2/4 mobile home feeder. It needs to be in conduit above ground and inside. And can be direct burial

 

[hoylebros]

Thanks Flexia. I've seen that mentioned on here doing a search.

Is this it?...http://www.lowes.com/pd_70203-295-13102915_0__?productId=4294349&Ntt=2-2-2-4+wire&pl=1&currentURL=%3FNtt%3D2-2-2-4%2Bwire&facetInfo=

 

[pattenp]

2-2-2-4 Al MHF as a branch feeder can be over current protected to no more than 90 amps. If you want a full 100 amp capacity you need to use #1 Al or #3 Cu.

The wire you linked to is SER, and is not the right wire.

This is MHF but the wrong size. Sometimes the store will carry 2-2-2-4 even though it's not listed on the web.
http://www.lowes.com/pd_70262-295-2...urrentURL=?Ntt=2-2-2-4+mobile+home&facetInfo=



8

 

[Stuart in MN]

There's another current discussion on this same topic here: http://www.garagejournal.com/forum/showthread.php?t=254586

 

[hoylebros]

2-2-2-4 Al MHF as a branch feeder can be over current protected to no more than 90 amps. If you want a full 100 amp capacity you need to use #1 Al or #3 Cu.

The wire you linked to is SER, and is not the right wire.

This is MHF but the wrong size. Sometimes the store will carry 2-2-2-4 even though it's not listed on the web.
http://www.lowes.com/pd_70262-295-2...urrentURL=?Ntt=2-2-2-4+mobile+home&facetInfo=



8

Thanks! So to use the 2-2-2-4 MHF I would need to put a 90a branch feeder in the main and a 100a disconnect in the shop? How do you guys feel about this wire being direct buried? I may just go ahead and run it in conduit to be safe.

 

[pattenp]

It really depends on the soil conditions. If rocky you will be best served to place it in conduit. For the long haul and insurance that the wire will last plus the ability to replace if needed, conduit is the way to go.

And yes, do use a 90A or less breaker in the main panel to protect the #2 MHF. The 100A main breaker in the sub-panel just serves as a disconnect.

Thanks! So to use the 2-2-2-4 MHF I would need to put a 90a branch feeder in the main and a 100a disconnect in the shop? How do you guys feel about this wire being direct buried? I may just go ahead and run it in conduit to be safe.

 

[hoylebros]

Thanks a ton pattenp! Using the MHF wire is going to save me some $$, and thanks for clearing up the info on using a 90A. I'm sure I will have more questions along the way, but this gives me a good start!

 

[pattenp]

The downside to using a 90A breaker is that it's not cheap because of not being a commonly used size. Once you pass a 60A breaker the prices go up sharply. You can buy a 100A breaker cheaper than a 90A breaker, because 100A is common.

 

[hoylebros]

Is this sufficient? It will be in a Square D panel...

http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-90-Amp-Two-Pole-Circuit-Breaker-HOM290CP/100206837#specifications

 

[pattenp]

That's fine if your house panel is a Square D Homeline panel.

Is this sufficient? It will be in a Square D panel...

http://www.homedepot.com/p/Square-D-by-Schneider-Electric-Homeline-90-Amp-Two-Pole-Circuit-Breaker-HOM290CP/100206837#specifications

 

[theoldwizard1]

If you go with MHF (recommended by the experts), use MUST you conduit where it comes out of the ground. Typically a sweep elbow from the bottom of the trench up the side of the building. To survive string trimmers and lawn mowers that sweep should be Schedule 80.

Conduit is require for MHF anywhere it is above ground, including inside buildings.

 

[hoylebros]

Thanks wizard. I think I've got it squared away. Now if they will ever get started with putting the building up!

 

[Aceman]

Don't direct bury it, use pvc, it's cheap.

All it takes is a vacuum, a walmart plastic grocery bag and some kite string and you can **** it through the pipe. Use the small string to pull in some bigger string or rope and use it to pull the cable through. It won't be a hard pull at 100' or so. Then you'll never have to worry about digging it up again should the wire fail. You can simply pull the old out and put new wire back in.