I am in the process of running new electricity to a camp house. The main panel is 125amps and is located on the meter pole and has a grounding rod. Right now there is one circuit for a well and one for outside lights.
My plan is to use a 125 circuit in the main, run ((3) – 2 hot , 1 neutral) #1 THHN copper in conduit 17ft. up the pole. From there splice to (2) #1 THHN copper and an exisiting bare neutral wire and run over head to the house which is less than 100ft. From the eave of the house splice to ((3) – 2 hot , 1 neutral) #1 THHN copper that goes inside the house to a 125amp subpanel. I was not planning on a main breaker for this panel, but I will have more than 6 circuits. I have the neutral bars seperated and one is wired to a grounding rod just outside the house.
I want to make sure this is correct, esp. the wire. Any comments would be helpful.
Thanks.
Replies
JRDE-
Well, a little knowledge is a dangerous thing. You're headed in the right direction, but it's a good thing you asked...
Wire size: the #1 copper in the conduit is probably too small. It depends on the temp rating of the breaker terminals. If the breaker terminals are rated at 60C, you need 1/0. But if the terminals are rated 75C, you're O.K. For the overhead portion, your #1 is rated at 195 amps (conductors in free air can shed a lot more heat than those in cable or pipe). But, what's the wind and snow loading like in the area? There's more to consider here than just ampacity. From an ampacity standpoint, you could use #4 copper THHW which has an ampacity of 125. And if the insulation is really THHN, it won't do for the overhead. Gotta be THHW, rated for wet. Most wire is dual THHN/THHW, but check. I'd use RHW, the rubber is a better cover for wet conditions in my opinion. But I can't tell you whether the copper will be strong enough. If I want overhead wires, I have the POCO run them. In fact, why don't you consider undergrounding the wire? Less chance of a tree branch taking them out...
House panel: You've got to put in a main breaker; because this is in effect a service for the building, Code requires a main if it takes more than "six motions" to cut all power from the panelboard. You ought to put in two ground rods (Code says two rods unless you can demonstrate that the resistance of a single rod is less than 25 ohms). I assume that there's no metallic path (other than the feeder wires overhead) between your service panel and the house panel. If so, and because you're not running an equipment grounding conductor with the feeder, you treat the house panel like a service panel--you bond the grounding bar and the neutral bar together. The grounding electrode conductor goes to the combined ground/neutral (which is bonded to the panelboard case).
Just FYI, if the second panel was in the same building as the service panel, you'd have to run four conductors and keep the ground and neutral bars separate in the subpanel. Or if you ran 4 conductors from bldg w/service to the second bldg, you'd keep ground and neutral separate in the subpanel (tie ground rid at second bldg to ground bar in subpanel). If there's any metallic path between buildings (water pipe, phone line, etc) you HAVE to run four wires and keep G separate from N in subpanel.
There are a lot of other details associated with this installation that are important. One is the method you're going to use to make the splices, and insulate them. Also how your'e going to support the wires. Watch out--if overhead wires fall, you've got severe electrocution hazard and fire hazard. The feeder breaker won't trip right away if the wires are arcing and dancing around on the ground. Ugly sight--like a nest of very deadly snakes.
I strongly suggest that if you are in an area where there is a building dept with inspectors, pull a permit and work with the inspector. You'll get a safer installation. If not--consider getting a licensed electrician to look at it on a consulting basis.
Good luck.
Cliff