LipschitzWrath
Active member
- Joined
- Feb 10, 2014
- Messages
- 29
Long time lurker, need some help. Just bought a new house and want to add a subpanel in the garage. I've been scouring the internet but can't find a lot of help because I feel like I've got some interesting design challenges.
Let's get the basics out of the way first. 200A main panel (at least a dozen breaker slots still open) in house in the finished basement. However, there is what I would describe as a service "crawlspace" or "raceway" (roughly 18" x 18") that runs from the main panel to the unfinished mechanical room in the basement of the house. This unfinished mechanical room shares a wall with the finished garage. I think there's a pretty good chance I can use this path to run a feeder to a subpanel with little/no drywall work.
Side note, this is the path that the previous owner used to run a 20A 240V plug to the garage (using 10/3 wire no less?). I do not believe this wiring installation meets code as he has exposed romex (or is it a cable of some kind?) in the garage feeding into the bottom of the 20A plug box.
Estimated distance from main box to where I'd put the surface mount sub is around 50'.
Anyways, I guess the first issue I need to address is that I am torn between a 60A or 100A service to the garage. I eventually have plans to run a Millermatic 211, which I've heard will eat 40A all by itself. I've then got some other big stuff I want to feed, like a 30A plug out to my camper and a 220V air compressor. I'd also like to add a couple 20A branch circuits for additional outlets in the garage, which is currently fed by a single 15A branch powering 4 outlets (5 counting the GDO). All this is making me question if a 60A sub would be limiting my options in the future. This has somewhat narrowed my research to seeing what it would take to do a 100A sub.
Assuming for a moment that I go 100A (open to discussion on that), I believe from my NEC research I have a couple options:
1.) #3 CU THHN in conduit.
2.) #1 AL THHN in conduit.
3.) #2 (or would it be #1?) CU cable (SER?), no conduit.
4.) #1/0 AL cable (SER?), no conduit.
Sound correct? Cheapest option turns out to be 4. Not set on the cheapest path, more worried about actually getting this done.
Now, for my design challenges. I don't think that I can get conduit to my main panel. There is that crawlspace but I'm thinking that it is going to be nigh impossible to for me to get into that space and run conduit into the top of the main box in such a small space. That pretty much eliminates options 1 & 2.
Option 3's main downside is cost. I think when I checked, that stuff was topping $6/ft. Beyond that, I hear it's hard to find and will be moderately difficult to work with.
Option 4 turns out to be the cheapest, but workability scares me. Wouldn't I be wrestling a python with 1/0, especially when terminating in the sub? It also appears there will at least need to be a short run of conduit from where it comes through the wall into the garage then turn 90 degrees and into the bottom of the surface mount sub. I'm worried about running such big cable through conduit, especially the bends. I could TRY to come in through the rear of the box, but I think access will be tight and I'd still be left with fighting the monster cable inside the sub. Same wrestling match would take place in the main panel to feed.
So, you can see my main conundrum is what type of wire to feed the sub with. Dropping down to 60A get's me more in the 6/3 range (cheaper/easier), but I mentioned I'm concerned about future expandability.
I've also briefly pondered switching wire types mid-run in a junction box, but then I wonder how you would splice 1/0 AL with #3 CU, for example. I can't seem to come up with a good solution.
What thoughts do you guys have?
Let's get the basics out of the way first. 200A main panel (at least a dozen breaker slots still open) in house in the finished basement. However, there is what I would describe as a service "crawlspace" or "raceway" (roughly 18" x 18") that runs from the main panel to the unfinished mechanical room in the basement of the house. This unfinished mechanical room shares a wall with the finished garage. I think there's a pretty good chance I can use this path to run a feeder to a subpanel with little/no drywall work.
Side note, this is the path that the previous owner used to run a 20A 240V plug to the garage (using 10/3 wire no less?). I do not believe this wiring installation meets code as he has exposed romex (or is it a cable of some kind?) in the garage feeding into the bottom of the 20A plug box.
Estimated distance from main box to where I'd put the surface mount sub is around 50'.
Anyways, I guess the first issue I need to address is that I am torn between a 60A or 100A service to the garage. I eventually have plans to run a Millermatic 211, which I've heard will eat 40A all by itself. I've then got some other big stuff I want to feed, like a 30A plug out to my camper and a 220V air compressor. I'd also like to add a couple 20A branch circuits for additional outlets in the garage, which is currently fed by a single 15A branch powering 4 outlets (5 counting the GDO). All this is making me question if a 60A sub would be limiting my options in the future. This has somewhat narrowed my research to seeing what it would take to do a 100A sub.
Assuming for a moment that I go 100A (open to discussion on that), I believe from my NEC research I have a couple options:
1.) #3 CU THHN in conduit.
2.) #1 AL THHN in conduit.
3.) #2 (or would it be #1?) CU cable (SER?), no conduit.
4.) #1/0 AL cable (SER?), no conduit.
Sound correct? Cheapest option turns out to be 4. Not set on the cheapest path, more worried about actually getting this done.
Now, for my design challenges. I don't think that I can get conduit to my main panel. There is that crawlspace but I'm thinking that it is going to be nigh impossible to for me to get into that space and run conduit into the top of the main box in such a small space. That pretty much eliminates options 1 & 2.
Option 3's main downside is cost. I think when I checked, that stuff was topping $6/ft. Beyond that, I hear it's hard to find and will be moderately difficult to work with.
Option 4 turns out to be the cheapest, but workability scares me. Wouldn't I be wrestling a python with 1/0, especially when terminating in the sub? It also appears there will at least need to be a short run of conduit from where it comes through the wall into the garage then turn 90 degrees and into the bottom of the surface mount sub. I'm worried about running such big cable through conduit, especially the bends. I could TRY to come in through the rear of the box, but I think access will be tight and I'd still be left with fighting the monster cable inside the sub. Same wrestling match would take place in the main panel to feed.
So, you can see my main conundrum is what type of wire to feed the sub with. Dropping down to 60A get's me more in the 6/3 range (cheaper/easier), but I mentioned I'm concerned about future expandability.
I've also briefly pondered switching wire types mid-run in a junction box, but then I wonder how you would splice 1/0 AL with #3 CU, for example. I can't seem to come up with a good solution.
What thoughts do you guys have?
