old 2 wire question to outlets and fixtures

[Anonymous]

I have a home built in early 60's that has 10g solid copper wire. Am going from 100amp service to 200 amp service. (need to have power for new home office addition that has new 3 wire installed)After talking to some contractors they say that I can use the 10g 2 wire and have recepticles wired to the boxes for grounds. The idea is that re-running new 3 wire is not really needed. The recepticle boxes are metal throughout the home. I really appreciate the help. :?

[imported_Ron]

If you ground the recepticles to the metal boxes, and the metal boxes are not effectively grounded, then the receptacles are not grounded.
Can you describe what type of cable is used? It is unusual to see #10 copper in a home for general receptacle circuits.

[Wgoodrich]

I also question if you really need a service upgrade. Have you performed a demand load calculation to discover if existing service is adequate or not. Are you guessing? What kind of loads in your office is so big that you need to upgrade your service?

Curious

Wg

[Kirby]

Sorry it is 12G solid wire and not 10. The extra service is for my office- 3 computers, fax machine, other electronic stuff, plus to power a woodworking shop in an out building. The load from home, office, and workshop would have put a large strain on 100amp service.
Also I do not believe the recepticle boxes are grounded. How can I check to make sure?
Again I apprecaite the help.

Kirby

[Wgoodrich]

You need to answer Ron's question letting us know the type cable or conduit running to your receptacles. Also tell us what color wires are inside that cable going to your receptacles.

In the mean time I suggest you go to the following link and calculate your demand load using that format. This will tell you if that 200 amp service you have decided on is too much or not enough. Guessing invites you to spend money on a useless project. Find what the NEC says is your minimum service size per the NEC rules using that demand load format below. Then you can make an informed decision as to what you should do concerning service size.

http://www.homewiringandmore.com/homewiringusa/2002/definitions/demandcalc02/DwlingDmdCalc02.html

Good Luck

Wg