Question for the electricians

I'm getting ready to start wiring my garage. I've got a Dayton 5 hp commercial compressor, What gauge wire do I need to use to feed it. The motor draws 30 amps at start up, what size or type breaker do I want to use. I also have a 30 amp knife switch to turn it on and off, will this be enough? I'm also am wiring a plug in for my welder, it's a Miller 35 wire feed and it looks like it needs a 40 amp breaker. What gauge wire do I need for it. The compressor will be 12 feet from the box and the welder plug will be about 20 feet. I've got a spool of 9/3w ground, will that be heavy enough? Thanks for any help you can give me.

10/2 romex for the compressor.....but is it a 220 Volt or a 120 Volt compressor? as far as breaker...depends on voltage, double pole 30 amp breaker/220V or single pole 30 amp breaker/120V....mine in a 220V Emglo and I ran a 10/3 romex...just to have a spare wire there.
The 30 amp disconnect swtch will work, mine is wired direct, panel not far away!
You said a commercial compressor......is it single phase or 3 phase?
9/3????? never heard of that....14 gauge = 15 amps, 12 gauge wire = 20 amps10 gauge wire = 30amps, 8gauge wire = 40 amps, 6 gauge wire= 50 amps

Mike R wrote:I'm getting ready to start wiring my garage. I've got a Dayton 5 hp commercial compressor, What gauge wire do I need to use to feed it. The motor draws 30 amps at start up, what size or type breaker do I want to use. I also have a 30 amp knife switch to turn it on and off, will this be enough? I'm also am wiring a plug in for my welder, it's a Miller 35 wire feed and it looks like it needs a 40 amp breaker. What gauge wire do I need for it. The compressor will be 12 feet from the box and the welder plug will be about 20 feet. I've got a spool of 9/3w ground, will that be heavy enough? Thanks for any help you can give me.

you will need 8 guage for both. motors you must allow 10% overage on wire size, so 33 amps. i/e 10 guage will not do.
will most likely just end up getting 8/3 even though for the compressor, and the welder you only need 2 current carrying conductors.

10 guage is good for 30 amps
8 guage is good for 45 amps

Breaker for the welder, use 40 amp. For the compressor you can use anything in a 40-60 amp range, Basically you use the smallest breaker that will allow it to start. Your startup currents, especially on single phase, can be up to 250% the full load current.
Depending on the type of panel you have a 60 will put you in a wide body breaker which takes up double the room in your panel box.
i dont know of any 9/3.. there is no such guage as 9, if its 8/3 that will be perfect.
30 amp knife switch will work.

Diggindeeper wrote:

Mike R wrote:I'm getting ready to start wiring my garage. I've got a Dayton 5 hp commercial compressor, What gauge wire do I need to use to feed it. The motor draws 30 amps at start up, what size or type breaker do I want to use. I also have a 30 amp knife switch to turn it on and off, will this be enough? I'm also am wiring a plug in for my welder, it's a Miller 35 wire feed and it looks like it needs a 40 amp breaker. What gauge wire do I need for it. The compressor will be 12 feet from the box and the welder plug will be about 20 feet. I've got a spool of 9/3w ground, will that be heavy enough? Thanks for any help you can give me.

you will need 8 guage for both. motors you must allow 10% overage on wire size, so 33 amps. i/e 10 guage will not do.
will most likely just end up getting 8/3 even though for the compressor, and the welder you only need 2 current carrying conductors.

10 guage is good for 30 amps
8 guage is good for 45 amps

Breaker for the welder, use 40 amp. For the compressor you can use anything in a 40-60 amp range, Basically you use the smallest breaker that will allow it to start. Your startup currents, especially on single phase, can be up to 250% the full load current.
Depending on the type of panel you have a 60 will put you in a wide body breaker which takes up double the room in your panel box.
i dont know of any 9/3.. there is no such guage as 9, if its 8/3 that will be perfect.
30 amp knife switch will work.

not doubting you, 10 wire has been working for my compressor for the last 10 years, wire not hot or even warm, breaker not hot. Its a 5hp,220v,FLA-30a on start up.

Overkill is not good on a breaker.

'65 T-BOLT wrote:

Diggindeeper wrote:

Mike R wrote:I'm getting ready to start wiring my garage. I've got a Dayton 5 hp commercial compressor, What gauge wire do I need to use to feed it. The motor draws 30 amps at start up, what size or type breaker do I want to use. I also have a 30 amp knife switch to turn it on and off, will this be enough? I'm also am wiring a plug in for my welder, it's a Miller 35 wire feed and it looks like it needs a 40 amp breaker. What gauge wire do I need for it. The compressor will be 12 feet from the box and the welder plug will be about 20 feet. I've got a spool of 9/3w ground, will that be heavy enough? Thanks for any help you can give me.

you will need 8 guage for both. motors you must allow 10% overage on wire size, so 33 amps. i/e 10 guage will not do.
will most likely just end up getting 8/3 even though for the compressor, and the welder you only need 2 current carrying conductors.

10 guage is good for 30 amps
8 guage is good for 45 amps

Breaker for the welder, use 40 amp. For the compressor you can use anything in a 40-60 amp range, Basically you use the smallest breaker that will allow it to start. Your startup currents, especially on single phase, can be up to 250% the full load current.
Depending on the type of panel you have a 60 will put you in a wide body breaker which takes up double the room in your panel box.
i dont know of any 9/3.. there is no such guage as 9, if its 8/3 that will be perfect.
30 amp knife switch will work.

not doubting you, 10 wire has been working for my compressor for the last 10 years, wire not hot or even warm, breaker not hot. Its a 5hp,220v,FLA-30a on start up.

I believe it works just fine.
Its just not the right way of doing it. Electric motors are a whole ballgame onto their own. The right way to do it is to have a motor starter with overloads on it, and a trip set breaker, but what average joe can afford to dump 2K on a motor starter for their shop compressor.

342g wrote:Overkill is not good on a breaker.

that would be true on every case with the exception of electric motors.

Thanks guys. 9/3 was a typo, I have a spool of 8/3. Yes the compressor is a single phase. Just a big, heavy, slow turning, long stroke, cast iron monster, nice and quiet. Hopefully I'll be able to get some holes drilled and some wire run this weekend, they say it's gonna be warm.