As described in detail, here (http://www.avsforum.com/avs-vb/showthread.php?t=782601) I'm converting my detached garage into my theater. One thing I need to improve is the electricity in the garage. Right now, there is one 15 amp circuit for the garage (I think) strung via a wire from the roof of the main house to the roof of the garage.

The house has a 100 amp panel, which is enough for the house. But I need, probably, close to 100amps for the garage, between the home theater, server rack, dedicated HVAC and the occasional power tool, etc.

It has been recommended that I get a 100amp sub-panel for the garage. That sounds good to me, though the installation price (as described in here (http://www.avsforum.com/avs-vb/showthread.php?t=782601)) is not ideal. But it actually makes a lot of economic sense if I can then NOT replace the main panel with a new, 200 amp panel.

Or do I need to do that, as well?

Here is the main panel for the house, right now:

http://preview.nathanh.photosite.com/~photos/tn/7556035_348.ts1168190248000.jpg

There is a bigger photo, with more detail, here (http://www.avsforum.com/avs-vb/showthread.php?t=782601).

I'm certainly no electrician, but I'm thinking you may need to upgrade your main panel. I think it mainly depends on how many total amps you think you may be using at any one time between your house and garage together. If you think you need 100 for the garage alone, then it seems like you'ld want to start with more in the main panel.

The subpanel would be fed out of the main panel, so would require another 100 amp double pole breaker (like your dryer one), and room for it in your main panel. If you don't upgrade, looks like you only have one open slot left, so you'ld need to double up two of your 20 amp circuits with another tandem breaker to free up another slot.

You're going to need some pretty beefy wire to support 100 amps as well (maybe #3 copper?). I think I had to use 6 gauge wire to supply a 60 amp subpanel when I added one to my basement (my house has 200 amp service).

Good luck, and I'll be curious to see what other opinions you get.

Bucky is right, you don't sum up all the breakers in the box and say I need x amount amp service. For example, old houses might have 60 amp service, that means that electricity is capable of coming into the house at 60 amps, but you might have breakers in the box that total over 100 amps. Like if you had a dryer at 30, ac at 30 and electric furnace at 40 or any other combination. You can have all sorts of breaker in the box for any quantity you want (smaller than the main (60)) but you can only use 60 amps at a time. Clear as mud?

So in the example above, you could run the dryer and the ac at the same time, but not the dryer and the heater. Got it? So your box needs to be sized for your total load. Lets say that when you went out to the theater you shut down the house entirely, then there is no load from the house and you could in theory devote your entire 100 amps to the theater. As long as when you're done with the movies your theater was shut down, and your house can resume normal operation!

In real life, there is AC, heaters, clocks refriferators that still run even while you are out, so you need to account for that.

As for a second box, I believe that the cable and breaker that supply that box need to be sized for the amp service you desire. Example, I've got a 40 amp box in my garage, the wire is big (can't tell what gauge its also really old) and the breaker from my main box is 40 amp.

Hope this helps, I'm no electrician, but I play one on TV ;)

Tboy

Hmmm. Yes, that is what I was afraid of. Looks like I need to get a new breaker box for the house, meaning coordination with PG&E to unhook and re-hook me, etc. Well, at least I know!

(Since this line of questions is not specifically related to creating a home theater, can anyone recommend a forum about home renovation issues, sort of the "home renovation" equivalent of what AVS Forum is for Home Theater?)

(Since this line of questions is not specifically related to creating a home theater, can anyone recommend a forum about home renovation issues, sort of the "home renovation" equivalent of what AVS Forum is for Home Theater?)
Its broader than just home renovation, but I like http://www.doityourself.com/ - it has articles on many topics, and lots of pretty narrowly-focused forums on just about any topic you might be interested in.

Thanks! Nice site.

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Related: I'd be curious to know what sort of amperage most folks here spec for their dedicated theater. I know it's strongly correlated to the equipment in use. But let's say that for now, I could run it all off a single 20 amp circuit -- but I'm SURE that now that my theater is moving from the living room to a dedicated theater in a detached garage I'll be expanding the gear. For example, I'll probably go back to two subwoofers, and might eventually get to four. Etc. Etc.

When I put together a dream list, 50amps seems like what I will need. Sound likely? (And then there is other stuff in the garage which means I'll need more amperage at times, I guess -- though it's unlikely I'd be using power tools at the same time as the theater!)

50 amps is a huge amount of electricity for a home theater- even in a garage! If your home has a 100 amp service then you have 2 legs of 100 amps apiece. And if you wanted to add more you'd have to have a sub panel installed. Talk to your service provider and see what the feasability of adding more would be......

50 amps is a huge amount of electricity for a home theater- even in a garage! If your home has a 100 amp service then you have 2 legs of 100 amps apiece. And if you wanted to add more you'd have to have a sub panel installed. Talk to your service provider and see what the feasability of adding more would be......

Hmmm. I'm not sure if I have two legs of 100 amps each, at present. It looks like 100amps total, to me. Can you tell? The bridged breaker on the right says 100 on each of the bridged halves and this seems to be the master breaker for the whole panel.

http://preview.nathanh.photosite.com/~photos/tn/7556035_1024.ts1168190248000.jpg

The other thing I'm thinking is that there appears to be one 20 amp? circuit for the garage right now. And if I replace the electric clothes dryer with a gas dryer, I could get two times 15 amp capacity freed up there -- and run at least one more circuit out to the garage?

Of course, I may be counting things wrong, since if you add up all the breakers in this box, you get more than 100 amps...

(For those reading this with dread regarding my lack of knowledge regarding electricity and wondering whether I'm going to fry myself or burn down my house, rest assured: I'll pay a professional to actually alter things and run wire. But I want to understand and know and direct how things end up working.)

Its fine to have the circuit breakers add up to more than 100 amps - I bet mine add up to maybe 400 amps for my 200 amp service. The real key is whether you think you would ever be using more than 100 total amps at the same time.

So if you replaced your dryer with gas, you could just as well run 2 new 20 amp circuits instead of 15 amp circuits if you wanted. You could also put in more tandem breakers (like the 15 amp ones you have now) if you wanted even more circuits, or wanted more while still keeping the dryer.

You just need to figure out what's the most you'ld ever need to use at one time. Maybe you'ld be fine with the 1 circuit you have now to the garage, plus a couple more added, if e.g., you decide that you won't ever run the dryer at the same time you use the theater.

Interesting. That makes sense but I never thought of it that way.

We might very well be doing laundry while watching a movie -- so getting the dryer off the electric grid and onto the gas grid makes sense.

But since there are only two of us, it's not like we'll have TVs going in every room, and multiple space heaters or AC units or what have you, and five teenagers using hair dryers all at once, etc etc, all at the same time. And the stove is gas. Gonna double check the hot water heater to make sure it is, as well. (We're not yet moved in, so if I forget to check something during one of the infrequent visits I have to wait a while before I can check again.)

So maybe I don't need a new main panel, or upgraded service! That will really help with the budget.

Now the question is: Do I still need a subpanel in the garage? Why / why not?

i would recommend putting a 60 Amp sub-panel in the garage. 60 amps is plenty for what you're wanting to do, and you can do it with your existing panel. if you have all those gas appliances then 100 amp service is plenty.

I think I can be convinced that 60amps is enough for the garage.

BUT

What is the advantage of having a sub-panel? Why not just run three or four circuits from the existing main panel, via romex (or other appropriate wire) of the appropriate size, out to the garage via a buried conduit?

What is the advantage of having a sub-panel?Only 1 wire to run out there (albeit a bigger one), and then future flexibility to be able to run as many circuits as you want out of your subpanel. Unless you know now exactly what you want for circuits and are reasonably sure you'll never want anything more or different.

For me, I was finishing off the half of the basement where my breaker box is located (including drywall ceiling), so knew I wouldn't have any access to run more wires in the future. So I put a 60 amp subpanel in the unfinished half of my basement as future-proofing for someday when I want to install the central vac unit, add circuit(s) for power tools in the workshop I want to have, etc.

Thanks. Makes sense. (Added cost, but makes sense :) .)

I just went through this for my new addition. I upgraded from 200 amps to 400 amps. I put in a new panel and the old one became the sub panel. I also had to bring everything up to code. The new code in my area requires an outside disconnect for each panel.

http://i61.photobucket.com/albums/h61/willygib/IMG_0724.jpg