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wiring a barn #4661
10/08/01 12:51 AM
10/08/01 12:51 AM
amp-man  Offline OP
Joined: Jun 2001
Posts: 141
Sacto, California US of A
Would appreciate your opinion on this--

A client has approached me to wire a 60' x 40' barn. It now has a 240V, 30A dedicated branch circuit supplying a well pump. Fed with 10/2 WG romex via 3/4" GRC underground from main panel at house (about 90').

Theere are now no other electricals in barn. Client would like to add a few fluorescent fixtures and a few general-use outlets. No plans for shop in the building, however, there is a partial second floor storage area that may be converted later to a mother-in-law apartment.

To meet immediate need, I propose to: pull out romex, pull in three AWG 8 THWN conductors (protected at main panel at 40A) to a new subpanel, using GRC as the EGC. Drive a ground rod. Bond panel to the well casing via galv supply pipe. Feed 240V to the pump from the subpanel. Wire in two 20A branch circuits--one for lights, one for plugs. Wiring in the barn will be exposed, so I will use MC cable. GFI receptacles.

Now, what if the client wants to instead run a bigger feeder (say 60-70A) to barn now to provide power to the future apartment? I'd run new GRC (or sched 80 w/4-wire feeder) to a barn subpanel. Should I leave well pump on the existing branch ckt from the main panel, or abandon the branch circuit and feed the pump from the new subpanel?

I don't see the requirement that a building have only one service as applicable here. This is not a service. I also do not see any obvious hazard from having a feeder and a branch circuit from the same panel come into the barn. Keep in mind that I would run both a neutral and an equipment grounding conductor to the subpanel (because the branch circuit conductors are parallel metallic paths between the two buildings. I didn't notice if the water pipe was galv. iron or PVC. If it's galv iron, another reason to run a 4-conductor feed).

Any thoughts about my general approach or the specific question?

Thanks in advance...

Work Gear for Electricians and the Trades
Re: wiring a barn #4662
10/08/01 03:36 PM
10/08/01 03:36 PM
sparky  Offline
Joined: Oct 2000
Posts: 5,372
215-2(B) comes to mind where it states 'feeder conductors', my Q would be just what would the plural of conductors refer to as applied to the 30A ?

How would the demand load calc reflect the futiure 'living area' apply , per 220 ?

i like the in-law idea!

are there any animals???

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Re: wiring a barn #4663
10/08/01 07:25 PM
10/08/01 07:25 PM
Tom  Offline
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
You're going to have to get rid of the circuit to the well if you go with the larger feeder. Article 225 deals with outside branch circuits & feeders & is frequently overlooked. You're right, you aren't running a service, but you're only allowed one feeder or one branch circuit (generally speaking). See 225-30(b)

You'll also need 2 ground rods unless you are able to test the rod resistance & it ends up less than 25 ohms.


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Re: wiring a barn #4664
10/08/01 08:25 PM
10/08/01 08:25 PM
amp-man  Offline OP
Joined: Jun 2001
Posts: 141
Sacto, California US of A
Tom & Sparky,

Thanks very much. Tom, I see that 225-30 is the pertinent requirement. My situation does not fit any of the exceptions. And your point about ground rods is well taken.

Sparky, no animals in the barn. It's more a storage area for boat, tractor, etc. I also thought about animals & ground currents.

Your thought on Sec 220 & load calcs is right on; I wouldn't install a new raceway & feeder until I got an idea of how the mother-in-law unit would be set up (HVAC load, kitchenette?). Although the MIL unit is "just a thought" right now, I want the client to be aware that the upgrade we're talking about will not give them the power for the apartment, IF they ever do it.

Work safe,



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