I have been wanting to upgrade my 100A service to 200A for quite some time. It's becoming a necessity since we've long ago run out of space in the box and I want more power to the garage which only has one 15A line to run the one light, one outlet and garage door opener.

I currently have two conduits from the house to the garage. One for high voltage, one for low voltage (ethernet and security cameras).

First question: If I upgrade to 200A, can I run a 100A breaker to a breaker box in the garage through the high voltage conduit? I imagine that's going to be a hard pull. Is that a good idea? Should I plan that differently?

Second question: Do I bond the ground and neutral at both boxes or just the one with the mains? I'm concerned about creating multiple paths to ground at fault. Or can i split the 100A before the main box?

Third question: is 100A enough for the garage. I'm thinking yes, even with running a stick welder and such.

I have 60a service to my garage via conduit.

Neutral from the garage to the house, garage ground is a driven rod (not back to the house).

Had this inspected and approved by an electrician.

As for 100a service, how big is the conduit? If it is proper size for the wire/load I don't see any issues. If it's too small, don't force it. It's not just physical size, you need sufficient room for the thermal dissipation.

I have 100 Amps to the garage. 2 hot and a neutral from the house and ground is at the garage. Also inspected and passed. I can’t remember, but I think we used 1.5 or 2 inch conduit.

I’ve run a welder, a lift, and woodworking tools without issues.

Ah, yes. I should have thought of separate grounds for the garage and house. That clears that up.

Both conduits are 2" pvc.

Mark,

I'm not an electrician or electrical engineer. However, my former home, built 1953, 1240SF with full unfinished basement, only had a 100A service. First thing we did after removing all the floor finishings from the house and repainting was to put in a 200A service. Our modern appliances were blowing circuits left and right and several needed to be reran/rebalanced. At the time I was quoted $1,800 and this was 20 years ago. The electrician went to our church and I think his wife brow beat him so he put it in for material costs...$200. Needless to say, I believe your home, unless it is really small, needs a 200A service and you should put another 100A to 200A in the garage depending on the loads you will need to supply.

As much as I hate to say it, we rely more and more on electricity and we all may end up driving an electric vehicle one day. I would at least plan for that and other considerations such as a generator hookup and a few 40-50AMP outlets for a welder like you stated and a dryer/stove for those unplanned renovations demanded by the wife down the road .

Last thing...grounds, grounds, grounds...you can never have enough. When I worked for the local electric company one summer and put in residential transformers, we had to put in no less than three copper-clad ground rods about 8-ft long, all tied together back to the transformer. If your home service is similar to mine, you probably only have a single ground rod.

Can you run 200 amps of service and split it 100 amps to the house panel and 100 amps to a garage panel? Might be an easier route.

quote:

Originally posted by jimmy123x:
Can you run 200 amps of service and split it 100 amps to the house panel and 100 amps to a garage panel? Might be an easier route.

This is basically what I have. I have 100amp coming off the pole to the meter on the house, and another 100amp circuit coming off the pole directly to the garage on a separate meter.

quote:

Originally posted by jimmy123x:
Can you run 200 amps of service and split it 100 amps to the house panel and 100 amps to a garage panel? Might be an easier route.

Well, we need more than 100A at the house alone. I need more outlets and there's no more room in the breaker box. I'm going to ask the guy doing the work what he thinks about that.

I don't think they will do a second meter at a single-family dwelling.

quote:

Originally posted by mark123:
Second question: Do I bond the ground and neutral at both boxes or just the one with the mains? I'm concerned about creating multiple paths to ground at fault. Or can i split the 100A before the main box?

You must only bond the grounded and grounding conductors in one place, at the meter disconnect or the box nearest to the main disconnect, if your meter base is not also a disconnect. Bonding in two places will create an alternate current path for the grounded neutral, and can create an unsafe condition as current travels on the bonded grounding system. IOW, you could create a situation where current is traveling on the cabinet of your refrigerator, dishwasher, etc. This current would be there all the time, not just during a fault. I think this is all covered in NEC Article 250.

You don't need to upgrade from 100a to 200 simply because you have no more space in your panel. You could free up space by using tandem breakers. When doing this, however, be sure to think about power usage on each circuit so you don't unbalance the panel. You want close as possible to equal loads on each phase. You could also install another 100A panel that simply has more spaces.