Electrical

[J.C.]

There is a workshop, an office and an old house, three separate buildings setting in a somewhat triangular orientation to each other. All three get their electricity from a single pole with a 100 amp box.

We're building a new house right beside the old one. (the old one will be torn down)

What I want to do is use the existing line (underground) from the 100 amp box to the old house and connect it to a 200 amp box for the new house. Can I do this without having to run a new line? I looked at the incoming line from the electric company pole. It said AWG 4 but it looked very small. The line going from the box to the old house is multi wire aluminum (about 160 feet) but I can't read anything to tell what it is. It is about the size of a penny, circumference wise. Also, can I keep the 100 amp box to supply the workshop and office and have a new 200 amp in the new house?

Thanks for your time.

[hallerb]

you spending megabucks on a new home, congrats.

You will need a new 200 amp main service in the new home and feed the old lines with a breaker sized to the wire to the other now sub panels, and probably have to upgrade those sub panels too with proper grounds and new panels.

once you begin changing things upgrading to current code is smart and may be required by law for excellent safety reasons.

Most likely all the existing stuff is old, time for a overall upgrade $ well spent!

[Doug Miller]

Probably not -- depends on what the existing line is, but it's doubtful that any electrician would have installed wiring heavy enough for 200A when your existing service is only 100A.

AWG 4 copper wire is fine for a 100A service entrance -- but can't be used for anything over that. You need a minimum of 2/0 copper, or 4/0 aluminum, for your new 200A service.

Keep looking -- it's there. Probably molded into the insulation, though, not painted or printed on it.

Meaningless. If you can accurately -- and safely -- measure the diameter of the conductor (not the insulation), then you can figure out what gauge it is.

Yes.

[hallerb]

Note depending on your existing setup you MAY have to upgrade those outbuildings, for codse compliance, but 100 AMP should serve them fine.

If your building a REALLY NICE home you might want to put the main service underground for appearance sake. Since the main service line from the road will need replaced anyway for 200 amp service.

I suggest you call your power company and ask them to take a look

[J.C.]

Thanks Doug, appreciate the help.

JC

[RBM]

Just to add to what Doug has already said: While the service conductors that you own, must meet NEC standards, it's common for utility company owned conductors to be much smaller, so it's not unusual to see thing like 1/0 aluminum connected to a 400 amp residential service

[J.C.]

I guess I'm confused. I thought the lower the number 1/0 versus 4/0 was the bigger wire.

JC

[Bud--]

getting larger:

4 3 2 1 0 = 1/0 00 = 2/0 000 = 3/0

-- bud--

[gfretwell]

This always happens in overhead service since they use the free air rule in the NESC but underground service laterals are usually going to follow 310.15(B)(6).

[RBM]

Utility companies, at least in NY do not use NEC standards, period

[gfretwell]

"NESC" was not a typo. It is the code utilities use. Different than NEC

[RBM]

Got ya, I'm not familiar with their rules. Con Edison of NY has their engineers decide if the size of a lateral is adequate for a service upgrade, unless of course when the customer owns the lateral, then it has to meet NEC, but once I connected a 200 amp service to #2 copper and once to #6, which was in a wooden duct from the street to the house

[Tom Horne, Electrician]

You need to read more carefully. The poster was referring to the National Electrical Safety Code (NESC) which is the standard that the nations utility regulatory bodies use in evaluating the safety of public electrical utility installations.