Wiring a shed.

Reply

  #1  
Old 01-22-14, 01:17 PM
Member
Thread Starter
Join Date: Jan 2014
Location: United States
Posts: 3
Wiring a shed.

Hi all,

I want to wire a shed with about 200 amps of power. My current main panel is 125 amp. I have a 200 amp meter socket with a 200 amp meter installed on the side of the house. This is being fed by an underground cable from the POCO. The meter is recessed into the siding of the house. On the inside of the house (on the other side of the wall, in the garage) the meter runs to the panel. I don't know what the cable gauge going into the main panel is. I already talked to the POCO about upgrading to a 320 amp service which they can do for me. I think the 320 amp service is actually a 400 amp service but I don't know for sure. I would need to replace the meter base with a 320 amp or a 400 amp base I think the POCO can tell me which one to go with as far as amperage is concerned.
I want to leave the main panel in the home the way it is and just put a 200 amp panel in the shed. I would need to dig a 120ft trench to the shed and run a 2" schedule 40 PVC pipe. I'm thinking a 4/0 4/0 2/0 cable to the shed should be enough. What type of cable would I need for that? I know I can't use an SEL cable as it is not rated for outdoor use. The other question is how do I hook it up so that the house panel does not need to be replaced? Do I run the shed cable to the meter? Does it need to go to a distribution box of some sort? Does the house panel need to be replaced?
I am planning on using a Cutler-Hammer BR panel with a surge protector in the shed. I will be installing six 240v 20a circuits with L6-20 plugs and eight 120v circuits with standard outlets. The reason I am going with 200 amps in the shed is I will be adding additional 240v circuits in the next 6 months. I will eventually want to use all the available power is the shed, at 80% load that would be 160amps total.

Any suggestions will be appreciated.
 
Attached Images   
Sponsored Links
  #2  
Old 01-22-14, 01:48 PM
Nashkat1's Avatar
Member
Join Date: Mar 2012
Location: USA
Posts: 8,470
Welcome to the forums!

I want to wire a shed with about 200 amps of power. My current main panel is 125 amp. I have a 200 amp meter socket with a 200 amp meter installed on the side of the house...

I already talked to the POCO about upgrading to a 320 amp service which they can do for me...

I want to leave the main panel in the home the way it is and just put a 200 amp panel in the shed. I would need to dig a 120ft trench to the shed and run a 2" schedule 40 PVC pipe. I'm thinking a 4/0 4/0 2/0 cable to the shed should be enough. What type of cable would I need for that?
The conduit will need to be Schedule 80 above ground or where otherwise subject to damage. If your going to run continuous conduit you should pull individual conductors in it, not cable. Cable that size is extremely difficult to work with anyway.

You need to feed the subpanel in the shed with two hots, a neutral and a ground. Three pieces of 4/0 copper THWN and one of 1/0 (I think) for the ground. Maybe 2/0.

The other question is how do I hook it up so that the house panel does not need to be replaced? Do I run the shed cable to the meter? Does it need to go to a distribution box of some sort?
The cleanest install - and cheapest and easiest - would probably to mount a weatherproof enclosure outside and use that to house to disconnects (breakers), one for the house and one for the shed.

Does the house panel need to be replaced?
Not necessarily, but you will need to make some changes to it. The GEC bond that should be there now should be relocated to the outside disconnect enclosure and a ground wire pulled into the panel from there. Inside your house panel, the neutrals will need to be isolated from ground and the grounds bonded to each other, the enclosure and the GEC conductor from the outside disconnect.
 
  #3  
Old 01-22-14, 01:57 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,357
Where is the disconnect for the house located now?
 
  #4  
Old 01-22-14, 05:28 PM
Member
Thread Starter
Join Date: Jan 2014
Location: United States
Posts: 3
That's a good question. I have no clue. I don't see one anywhere. The only disconnect is for the A/C at the back of the house.
 
  #5  
Old 01-22-14, 06:05 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 14,357
It is the top left breaker with the hold down screw in it. I didn't see it initially. The services need to be grouped so you may need to make some changes to your panel.
 
  #6  
Old 01-22-14, 07:02 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,213
My opinion: You need to use a 320 amp meter socket with two 200 amp breakers factory installed (Milbank makes these), check to be sure your power company allows and specifies the proper socket. I'd change one breaker to a 125 amp and feed the house service panel from this one. The existing 125 amp panel will become a subpanel so you'll feed it with 3 - #2 copper and a #6 copper ground. The neutral bar will have to be isolated from ground and you'll have to install an accessory auxilliary ground bar in that existing panel and move all ground wires to that new ground bar. Feed the shed panel from the other 200 amp breaker with either 3 - #2/0 copper THWN conductors and a #6 ground or 3 - #4/0 aluminum XHHW conductors and a #4 ground. At the shed you have to drive a ground rod and connect it to an accessory auxilliary ground bar in the 200 amp main breaker panel with #6 copper ground wire. Do not bond the neutral bar in the panel to the box as this is also a subpanel. At the meter socket, drive one or two ground rods (consult your AHJ) and connect them to the neutral bar in the socket with #6 copper ground wire. Also from the socket neutral bar you will run a #1/0 copper ground wire to within 5 feet of where the water service enters the house, jump around any meters or pressure reducing valves with the appropriate water pipe clamps. Any ground wires currently grounding the existing 125 amp panel must be removed.

The socket with the two main breakers satisfies the grouping requirement PCboss mentioned.

You will have to provide your power company with any increase in load. They may or may not increase the service lateral depending on the loads you provide them. There may be power company charges associated with this work, consult them. Many municipalities will issue homeowner electrical permits, but few will issue a homeowner permit to change a service.
 
  #7  
Old 01-22-14, 09:08 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 235
Wiring Shed

You should check with you AHJ about the size of conductors for your 200 amp feeder to the shed. 310.15(B)(6) would allow the use of 2/0 CU for a 200amp feeder but that article specifically states that it is for individual dwelling units that are one, two or multi family (such as apartments) and not for other structures on a residential property. You may be required to run 200 amp conductors per 310.16 and not 310.15(B)(6). It would be worth checking on with the local AHJ. A shed does not meet the definition of a dwelling unit under the NEC. Your 125A feeder conductors should be ok since they handles the total load of the dwelling.
 
  #8  
Old 01-22-14, 10:47 PM
Member
Thread Starter
Join Date: Jan 2014
Location: United States
Posts: 3
First off thank you guys for your input. It is greatly appreciated.

CasualJoe - Wow that's a lot to take in. I had to reread your post about five times before it started sinking in. I get everything you are saying. This sounds like a lot of work. I think ill need some help with this project. The Millbank meter base that you are talking about is it the U5844-PXL-200?
I already checked with the power company. They will need to rerun a new underground cable. They will use the existing conduit. I also talked to the city inspector about this project and I think I need to call him again.

Bahtah- looking at the NEC schedule, they both list the 4/0 aluminum 90c cable as rated for 205 amps, so I don't think it matters which schedule as that specific cable is listed on both schedules, BUT I am not an electrician so what do I know.
 
  #9  
Old 01-22-14, 11:16 PM
Member
Join Date: Oct 2013
Location: United States
Posts: 235
Wiring Shed

Bahtah- looking at the NEC schedule, they both list the 4/0 aluminum 90c cable as rated for 205 amps, so I don't think it matters which schedule as that specific cable is listed on both schedules, BUT I am not an electrician so what do I know

You cannot use 90-deg C to determine the ampacity of the 4/0 aluminum.110.14(C)(1) your 4/0 ampacity would be 180 amps at 75-deg C, Lugs on your breaker will be 75-deg C)but you can protect it with the next standard size breaker or fuse which would be 200amps per 240.6(A). You cannot use 2/0 copper (thats what I wanted to call your attention too in case you wanted copper)for 200A on your feeder, you would have to go to 3/0 CU which is big bucks.
 
  #10  
Old 01-23-14, 04:46 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: USA
Posts: 9,213
You cannot use 2/0 copper (thats what I wanted to call your attention too in case you wanted copper)for 200A on your feeder, you would have to go to 3/0 CU which is big bucks.
That is correct. Technically the service entrance wiring stops at the service disconnect which would be the two 200 amp breakers in the meter socket. I believe Milbank busses the power to the breaker disconnects. That being said, the AHJ will tell the OP whether they will require 2/0 or the full sized 3/0 copper conductors to the shed subpanel. Most people would use the 4/0 aluminum conductors, as I would.

The Millbank meter base that you are talking about is it the U5844-PXL-200?
No, that's a 200 amp socket with one 200 amp breaker factory installed. I'll have to look for a catalog number for the 320 amp socket.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'