Subpanel questions

[Ironhorse74]

Hi all. I want to run a 125 amp sub panel in my shop. I have two 200 amp panels in my garage. One runs the house the other was always intended to run a shop. The shop is 160 feet total. That includes the length of the run into and out of the trench. My plan is to have three number 2 copper thhn conductors. Two ground rods at the shop. I will be running it in 2" pvc conduit. The code I have to install to is NEC 2014. What do you sparkys think?

Thanks

Brad

 

[Elginz]

Some one can jump in here, but I think you need a ground wire as well, for four wires total.

 

[dfiler2]

Here is a good diagram showing what needs to be done.

 

[wyliesdiesels]

Yes u need 4-wire- 2 hots neutral and EGC/ground.

#2 CU is not large enough as its only rated for 115a.

U will need #1 CU with a #6 EGC.

Voltage drop isnt a problem over that distance.

That will cost some serious dough!

I would go with AL wire.

Are u sure u need 125a?

What equipment will u have?

Is this a one man shop?

Dont forget to isolate the neutral bar in the subpanel. U may need to buy a ground bar kit.

 

[pattenp]

The most economical choice of wire is 2/0-2/0/2/0-1 AL MHF (Mobile Home Feeder) it's good to 135A.

See this... http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet15

Edit: The above chart shows 150A for the 2/0, but that is only when used as a service entry supplying the total load to a dwelling. As a branch feeder it's 135A.

 

[Ironhorse74]

Yes u need 4-wire- 2 hots neutral and EGC/ground.

#2 CU is not large enough as its only rated for 115a.

U will need #1 CU with a #6 EGC.

Voltage drop isnt a problem over that distance.

That will cost some serious dough!

I would go with AL wire.

Are u sure u need 125a?

What equipment will u have?

Is this a one man shop?

Dont forget to isolate the neutral bar in the subpanel. U may need to buy a ground bar kit.

There lies the problem. It is a one man shop. There will be some loads that will only be used one at a time, welder, plasma cutter, lathe, mill. While running any of those there coul also be the loads from air compressor and mini split. I aslo have the option of bringing in another 200 amp main. It is a shorter run but there are some big costs associated with it.

Brad

 

[theoldwizard1]

There lies the problem. It is a one man shop. There will be some loads that will only be used one at a time, welder, plasma cutter, lathe, mill. While running any of those there could also be the loads from air compressor and mini split.

Wylie is correct. Most one man shops only need about 60A, even with a mini split heat pump. Your wild card is the plasma cutter, which requires compressed air.

Figure out worst case and I'll bet you only need 90A. Of course, if you turn off the heat pump for the short period of time you are running the plasma cutter/air compressor, 60A will likely be enough.