Feed wire sizing to my garage

What Jim said. Check your local electrical code. Most all local codes are based on the national electric code. So mostly everywhere is similar. It will tell you what depth to bury, wire size for amperage, etc.

I just did what you contemplate and dug a 36" deep trench 100' in two days with a rented trencher and a 4" trench shovels -these things are great! I used 3" grey plastic conduit - which was the cheapest part of the job- it is WAY easier to pull wire through the bigger the diameter.

Regarding outlets and circuits. It only took me 1 year to want more outlets. And I installed plenty, with a big elaborate shop design plan. This spring, I get to open up last years some Sheetrock and put in more wiring... hint, hint.

Also call before you dig...
 
I don't believe I have ever heard anyone saying something like "I wish I had run less power to my shop". I have a relatively small shop ~576 sq feet with 100 Amp sub panel and every breaker is used. Most of my stationary tools are wired for 220V.
 
My original plan was to run a buzz box and DP.
Things grew from there.
I ran 6. Should have run 4.
I occasionally have to go to the main panel in the house to reset a breaker.
Arrgh.

Daryl
MN
 
Personally? I'd go with 2-2-2-4 and a 100 amp sub panel. Just doing enough to get by for "today" will probably come back to bite you in the posterior "tomorrow."
 
If you are using 240VAC for the VFD, the breaker would need to be ganged, both legs would trip. I would not run 120 and 240 off of the same breaker. You might be able to put in an electrical sub panel for future upgrade and have two single pole 120VAC breakers and a separate 240 VAC ganged breaker.

Like the others have mentioned, if you are going through all the trouble to trench and put in a new sub panel, then I would pull a minimum of a 100A line. I ran #4 copper wire in 1.5" ABS electrical conduit to my garage (about 40') and put in a 100A sub-panel. I believe code would require #3 wire for 100A breaker at the main panel (I use an 80A breaker at the main breaker box). All the sub panel breaker slots are filled and I recently had to put in a quad pole circuit breaker for a compressor and two 120VAC circuits. The VFD will give you soft start, so you do not have the motor start current that needs a bigger breaker. I think you would have too much voltage drop using #12 wire running a machine and anything else. I would also go a bit bigger on the conduit, you need to review the electrical code with regard to the fill volume (wires size and number) that can be pulled through the conduit.

I recently put in a Champion 5Hp compressor, they specify a 50A breaker. It is surprisingly quiet, it uses a low speed motor and air pump, and I can barely hear it outside of my garage. There is also the California Air compressors if you do not need higher volumes of air, they have about the same noise level as your mill when running.
 
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More is better. When I set up the shop, I ran a 60 amp subpanel. I wish it had been 100.

And while you're running the receptacles, use 12 ga. wire, and 20 amp breakers. 14 ga./15 amp just doesn't cut it. And make sure the receptacles are 20 amp, as well.
 
Not exactly on topic but ..

I just changed out my workshop (cubby hole) lighting for led flurecesent fitting of 50w, it has a maintained live and a battery that will keep half the lights on for upto 3h if the power drops might be worth considering if your going to be working at night in the dark surrounded by spinny and sharp things :)

They have got a lot cheeper, and you can get a small bulk head light as a very cheep one juat to give enough light to find your way out.

Stuart
 
I don't believe I have ever heard anyone saying something like "I wish I had run less power to my shop". I have a relatively small shop ~576 sq feet with 100 Amp sub panel and every breaker is used. Most of my stationary tools are wired for 220V.

I did a 100a panel and am tickled
 
I run my entire setup off of 240 volt, 20 amp. No issues at all.

My vote says use what you have until there is a problem, then upgrade.


Sent from my iPhone using Tapatalk
 
So to answer the original question, the recommended wire for a 240 VAC single phase input 1Hp (0.75 kW) VFD is 12-14AWG with a recommended breaker/fuse of 15A. Assuming a 15A draw at 240 VAC the voltage drop for 70 feet of 12 AWG wire is about 1.4%, at 120 VAC it is 2.8%. The The NEC maximum conductor voltage drop recommended for both the feeder and branch circuit is 5 percent of the voltage source. So with a 20A main panel breaker feeding your 12AWG branch circuit to your detached garage should be OK, I still would consider a sub panel and breaking out two 120VAC separate 15A single pole breaker socket circuits for each set of 4 outlets, and a 15A double breaker for a 240 VAC circuit. I also believe there is a requirement for all garage outlets to be on a GFI, the standard big box store GFI's usually trip when a VFD is attached to it.
 
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