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Wire and Breaker Size for 3 hp motor

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Blog entry by hokieman posted 1657 days ago 14234 reads 0 times favorited 11 comments Add to Favorites Watch

I am looking for some guidance on wire and breaker size to wire up my 220 volt 3 hp table saw. I will have to install a subpanel on the other side of my house to get to my garage and the wire run will be about 120 feet. Are there any electricians or electrical engineers that can help me out? What size wire and breakers do I need to install in the subpanel? I have seen similar posts on this site before but I can’t find them. Thanks.



11 comments so far

View lew's profile

lew

9827 posts in 2255 days


#1 posted 1657 days ago

I had a Scuba Air compressor that was about the same distance from the panel. It was a 220v single phase 5 hp. The electrician used 10/3 w ground and a double 20 amp breaker (one for each leg)

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View NBeener's profile

NBeener

4806 posts in 1674 days


#2 posted 1657 days ago

How many amps is the TS rated to draw @ 220V?

My (not an electrician, though I did study electrical engineering … eons ago … in college) gut says that Lew’s answer’s gonna be a good one, but I can probably do a bit better, given the amperage.

-- -- Neil

View jonah's profile

jonah

302 posts in 1798 days


#3 posted 1657 days ago

12AWG wire is rated to carry 20A, and 10AWG is rated for 30A. The maximum amperage is not dependent on the voltage, since in residential wiring each individual wire always carries 120V. A 20-amp breaker will be more than sufficient for the saw, but if you’re going to run other equipment off the sub-panel you’ll need more than just a 20A circuit

Based on your post, I would not really recommend trying to install a sub-panel yourself. It’s not difficult to do, but it’s a bit harder than just installing a breaker or a new outlet. Also, if you need more than one circuit, you’ll have to use 8-gauge or thicker wire, and that stuff is absurdly difficult to work with, compared to normal 14 or 12AWG wire. Hiring an electrician to do it shouldn’t be too bad (maybe 2 hours of work).

View lew's profile

lew

9827 posts in 2255 days


#4 posted 1657 days ago

The electrician, that wired my compressor, used 10 gauge wire because of the extra long distance. He felt that 12 gauge may have had too much of a voltage drop for that distance.

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View bigike's profile

bigike

4028 posts in 1788 days


#5 posted 1657 days ago

i talked to an electrician in the family and he told me to use the 20amp double breaker and nomex 14/2 wire my saw works fine i have a 3hp 1ph delta unisaw this is the stuff i used with a little help from an electrician he also helped me wire my first work shop over the phone that is same here with when i got my saw but u might want to use conduit where as your going to a garage hope this helps.

-- Ike, Big Daddies Woodshop, http://www.icombadaniels@yahoo.com

View Craftsman on the lake's profile

Craftsman on the lake

2256 posts in 1937 days


#6 posted 1657 days ago

I’d use double 20 amp breakers and #10 wire. The wire size is good to work with so why not use it instead of #12.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View TopamaxSurvivor's profile

TopamaxSurvivor

14399 posts in 2176 days


#7 posted 1657 days ago

The code says to use a #10 wire and a 35 amp breakeer for 3 hp at 220 v single phase. If I were going to run a subpanel, I would go 100 amp, using #3 cu or #1 Al. Running that far, if yiou are goin gto just wire the saw, I’d use #8 or even 6 to allow for voltage drop. The saw will probably sound a little sick and maybe be a little slow starting on #10.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Devildog's profile

Devildog

12 posts in 1881 days


#8 posted 1654 days ago

I would agree with TopamaxSurvivor, as what he described is show I ran the wire for the sub panel in my shop. My shop is approx 100 feet from my main panel, I contacted a electrician who incidentlly was a friend who told me what to get. I used the #1 aluminum, a 100amp breaker in the main panel to a 100amp sub panel, all the wiring in my shop is either behind the walls just like residential wiring for 110v or through conduit for 220v. I have no flicker in the lighting when I turn on any equipment to include the stuff that operates on 220v. I hope this helps you out.

-- Terry Williamsport PA

View Devildog's profile

Devildog

12 posts in 1881 days


#9 posted 1654 days ago

Oh sorry I forgot to add what size breaker for your saw. First check to see what your saw motor requires for amperage there should be two different requirements one for start up and one for operating draw, for most saws the start up draw will be more than the operating draw, if your saw draws 15 amps at start up a 20 amp breaker will do just fine, if it draws 20 amps then you need to go with a 30 amp breaker, hopefully you have the idea by now. Hope this helps

-- Terry Williamsport PA

View dhanna6's profile

dhanna6

1 post in 1130 days


#10 posted 1130 days ago

I don’t want to hijack the original posters thread but I have a question regarding an air compressor. I have a 3.5 HP single phase motor that says 15 amps on the motor sticker. I ran 10-3 wire from my panel to a disconnect box and the wire run was 55 feet. I installed a 20 double pole breaker in the panel. Will that be a big enough breaker to keep it from tripping on start up?

View TopamaxSurvivor's profile

TopamaxSurvivor

14399 posts in 2176 days


#11 posted 1130 days ago

Maybe?? May have to go to 30.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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