I’ve got a detached single garage I’m using as a workshop. Right now, it is supplied with a single 15 amp circuit. Distance from house panel to garage sub panel is about 40′.
I have decent “job site” type tools: Bosch table saw in Rousseau stand, sliding miter saw on stand, router table, compressor, etc. If I’m using the table saw and the shop vac at the same time, the breaker pops. Clearly, things have to change.
This is only for personal, non-production use. I’d like to run the tools, lights, future upgrade to install an electric baseboard or radiant heater, and who knows, maybe a small fridge?
Here are the existing parts that I already have in place in anticipation of upgrading: 8 gauge 3 conductor plus ground cable (free!) run through 2″ plastic conduit, and an unused 50 amp breaker in my panel.
Is the 8 okay for a 50 amp breaker? If not, replace the breaker w. smaller, or buy new cable? What do I need?
Note: I will be getting professional help, but want a plan first.
thanks.
Amateurs talk strategy, Generals talk logistics.
Replies
If the wire is rated for 75C and the terminals on the breaker and the connections at the sub-panel are rated at 75C then #8 is good for 50 amps. Otherwise 40.
You can find the rating on the breaker, but you will probably have to pop it out.
And most wire today is 75C or better, but you need to check the markings on it.
William the Geezer, the sequel to Billy the Kid - Shoe
A few further details would be needed...
1. The #8... copper or aluminum? However, it's kind of moot for the following reason... For a feeder (which is what you call the conductors used in the manner we're talking), #8 Cu is protected by a 40A breaker, #8 Al is 30A. So 50A breaker is too big either way.
2. Additionally, you need to worry about insulation type on the individual conductors. Is it THWN or other insulation rated for use in wet locations? I'm assuming (maybe incorrectly) that the conduit is running underground to the detached garage. If so, in my location the insulation must be rated for wet locations (even though it's in conduit), so no THHN... THWN, and other wet-rated are allowed.
Note that #8 will work okay for your equipment ground between the main and subpanel so long as you stay under 100A breaker size for the sub.
FWIW, I have a two-car detached garage that I have a mid-sized air compressor, a small MIG welder, tablesaw, portable planer, shop vac, etc. I've been fine with a 60A subpanel, fed by #6 Cu THWN individual conductors (not cable) in 1-1/2" conduit to make the pull easy. I have a short run also, so voltage drop wasn't really a concern.
Actually, just saw Bill's post. He's right (about 75deg). I'm tired and messing up...
Thank you Rusty and Bill. Time to go read some labels.Amateurs talk strategy, Generals talk logistics.