Newbie Here! 220v Compressor Wiring Question

[Rex Kramer]

Greetings all!

New here, but have been lurking for a while. I told my brother in law about wanting to put a compressor in the garage and he referred me to this site (thanx a lot 6530!)

Please forgive me if this question has been asked 10,000 times, but my search-fu is apparently weak. So here it goes:

I was originally looking at 110v compressors as that is all I had in my garage. I am having an electrician come in to install some things and I was going to see about wiring the garage for 220v to run a more powerful compressor. Now that I have decided I want a 220v compressor I have more than confused myself (110 was easy.. for the most part, just plug it in).

The compressors I am looking at are on the smaller side of the 220v scale. Single stage, approx 3-5HP, 10-11.5CFM range, 60gal tanks. I am wondering what amp the circuit needs to be for a compressor in this range. I have read spec sheets showing 15-20a, but I don't know if that includes a surge during start up. Would a 30a circuit be overkill for a compressor that is rated for 20a? Or is it not enough?

Also, I noticed reading through posts that some (most?) of the 220v compressors do not come wired for a plug. Do most people hard wire them or do they wire a plug onto the compressor and plug it into a 220v outlet.

My plan was to have the electrician come out and install a 220v outlet in the garage and buy a compressor later in the year, but I want to make sure I have him put in large enough wire (10ga?) and breaker to handle a compressor that pulls 20a.

FWIW I do not plan on doing any welding or anything other than having a compressor on this circuit. It will be a dedicated line from the breaker box.

Any help with this would be appreciated!

And I must say, incredible site... I have been literally overwhelmed by the amount of information here. And the garages some of y'all have are amazing.

 

[kb2tha]

I am considering a 5hp compressor that draws 16.8 amps. Since startup would put it very close to or over 20 amps, I will wire it with 10/2 wire with a 30 amp breaker.

If you go this route you need a 30amp double pole breaker. You will have two hot leads and a ground. Hook the black and the white to the two points of contact on the breaker. Make sure to mark with a black permanent marker or black electrician's tape the white line as it hooks to the breaker. It will be a hot line, so must identify as such.

If you do a 30 amp breaker, make sure your wire is sized appropriately.
Ken

 

[Ign]

Even my 80gal Craftsman needs a 30A breaker. #10 is fine. I forget my HP rating but it was back when Sears used their new math to make their specs look better.

You're supposed to have a "disconnect device." This can be your plug. If you hardwire it, you need to have a switch elsewhere. The breaker does not count as a switch.

 

[Rex Kramer]

Even my 80gal Craftsman needs a 30A breaker. #10 is fine. I forget my HP rating but it was back when Sears used their new math to make their specs look better.

You're supposed to have a "disconnect device." This can be your plug. If you hardwire it, you need to have a switch elsewhere. The breaker does not count as a switch.

Thanks both of you for the information.

For the disconnect device, what do most people do? You either install some kind of switch or just plug it in when you want to use it and unplug when done?

 

[Rex Kramer]

As a followup, I am reading that 10/2 would be fine for a compressor. Is there any reason not to have 10/3 installed for future use with something other than a compressor? I doubt I'll be in this house forever and giving the next owner flexibility isn't a bad idea when it comes time to sell.

 

[MrMark]

I am considering a 5hp compressor that draws 16.8 amps. Since startup would put it very close to or over 20 amps, I will wire it with 10/2 wire with a 30 amp breaker.

If you go this route you need a 30amp double pole breaker. You will have two hot leads and a ground. Hook the black and the white to the two points of contact on the breaker. Make sure to mark with a black permanent marker or black electrician's tape the white line as it hooks to the breaker. It will be a hot line, so must identify as such.

If you do a 30 amp breaker, make sure your wire is sized appropriately.
Ken

Start up would be more like 80 amps, maybe a lot more. That has nothing to do with your breaker and wire requirements, though. The breakers used are inverse time delay and have trip curves that allow for the high inrush currents on electrical motors.

 

[MrMark]

As a followup, I am reading that 10/2 would be fine for a compressor. Is there any reason not to have 10/3 installed for future use with something other than a compressor? I doubt I'll be in this house forever and giving the next owner flexibility isn't a bad idea when it comes time to sell.

That's what I would do. Nothing wrong there. I would use a plug on this one too. I wouldn't hard wire it unless it was essentially industrial. If I didn't have the compressor yet, and therefore didn't know its specs, I would use 8 gauge wire, which can be used with a 40 amp breaker.

 

[nissan_crawler]

I ran 6 gauge to all of my 240 outlets (4) in the garage. I also ran 3 wire w/ground, even though I didn't need it. Just use the appropriate receptacle and breaker, then. After that, if you get a bigger appliance, it's a matter of swapping the breaker and outlet.

Just my $.02

 

[Rex Kramer]

Thanks again guys. I think I will have the wire upsized somewhat beyond what I think I'll need (but I'm sure I'll NEVER need anything larger, right? ) and just breaker appropriately for the compressor that I put on it.

 

[Ign]

The choice is yours.........you only need two hots and a ground, and most any garage/fab item is only gonna need this too.

Since the compressor is an auto-start device it should also be on a dedicated circuit.

If it were me, in the interest of time, money and ease of install, I'd just run 10/2 and be done w it. SOOO much easier to pull 10 than 8 or 6, and definitely cheaper too. And of course the fewer wires, the easier it is.

That said, for one recep the additional cost is negligible if you want to step up. It's your money.

I ran #6 for all my plasma/welder receps, but where I could save myself some work I stepped down; specifically compressor, 2 post lift, infrared heater, mill, RPC.