electricalknob-and-tubeUtilities
I have to upgrade my electrical service panel from knob & tube to current grounded code. The house is on bedrock and ground is the water pipe entry in the garage more than thirty feet away. Now it appears the service panel may need to be relocated due to the proximity of the gas service meter. The house was built in 1956, in San Mateo County, California.
What should I do about this situation?
To directly answer your question: yes, you can use a 50 amp breaker for another purpose.
Also, just to be clear, the total of all breakers in a panel can be higher than the main breaker protecting them -- it just means you can't have more than 100A being used at the same time. Most people don't generally use their stove, dryer, hot tub, furnace, table saw and have every light and electrical appliance in the house on all at the same time anyway, so usually this isn't an issue.
For your garage, you also need to be concerned about the size of wire, and physically getting it to the garage. There are lots of good questions on this that I'd recommend you browse through: https://diy.stackexchange.com/search?q=detached+garage+subpanel
To identify the wire gauge, the best way might be to take the cover off of the breaker box (advise to do this with power off for safety, but power can be left on - proceed at your own risk) and see if there are any indications on the wire sheathing. If there isn't, use a guide like to identify the gauge of wire.
As for copper vs. aluminum wire, aluminum might be cheaper in larger sizes. However, aluminum requires some special anti-oxident joint compound when you make connections with aluminum wire (see Ideal no-alox for an example of this stuff). If you don't use the compound, its possible that the connections will fail over time.
EDIT: Using the info you provided in the comments, and the wire voltage drop calculator at http://www.southwire.com/support/voltage-drop-calculator.htm, assuming:
- Single Phase 240V
- Direct Burial
- no more than 3% voltage drop
- 2 AWG aluminum wire
Your wire gauge will allow you to maximum run somewhere in the 75-80 amp range. I wouldn't go all the way to 100 amps, but 60 amp service should work. You'll need 1 AWG wire to run 100 amps safely that distance.
Best Answer
I would contend that the gas meter was installed in the wrong place. It clearly was installed long after the house was built and the original electrical panel installed. I would first ask the gas utility to move their mater. I would state that a 'home inspection' found the situation a hazard and are now asking to have the gas meter moved out of safety concerns. In fact, 'my' home owners insurance may become void without reparations. It doesn't hurt to try. They certainly have more resources to make this kind of a change than you do; not to mention the fact that they are the ones that put the meter is a hazardous and non-code compliant location. If you wanted to get hard nosed about it, I am sure you could find a lawyer who would love to help.