How did you wire your 5 HP air compressor
- Thread starter Ross/Kzoo
- Start date
jaker10
Well-known member
Just like that.
Alexbn921
Well-known member
#12 should be find. Voltage goes up current goes down. As long as the wire is not to long 100+ ft.
Aceman
Well-known member
You need to hardwire it. Despite what others have done, it's not correct. Even a 50 amp receptacle only carries a 3HP rating. Obviously, a 20 or 30 amp recep will be even less.
You will need either #10 THHN in conduit or #10-2 MC or #8-2 Romex. Make the connection to air compressor with a short piece of flex for vibration.
You will need either #10 THHN in conduit or #10-2 MC or #8-2 Romex. Make the connection to air compressor with a short piece of flex for vibration.
Aceman
Well-known member
If THHN, you can use black, red, and green. If it's MC cable or Romex, you'll only have a black, white and ground. But you can tape the white wire red.
sberry
Banned
I have seen them run like that for years but you should have a wire up a size anyway if its really near 5 hp.
sberry
Banned
There are different models, one is more like 3.2 but lists it at 5
wyliesdiesels
Well-known member
For motor circuits, wire should be 125% of motor FLC, based on NEC tables(in your case 28a), and breakers can be max 250% of FLC. Breakers are oversized due to motor inrush/startup current. U could pobably get by with a 50a breaker but may need to go higher if u have nuissance trips!
Kevin54
MEMBER EMERITUS
I have mine wired with #12 and into an outlet. It's the same wire they use for electrical drops where I worked to hook up mills and lathes. I've never had a bit or problem with it and nothing ever got warm, like the cord or plug. One of the shops electricians wired it for me.
wyliesdiesels
Well-known member
What size is your compressor?
Kevin54
MEMBER EMERITUS
5 horse / 80 gallon 2 stage
pattenp
Well-known member
This is what the NEC calls for so take it for what it's worth. If the motor data plate says 5 hp the supply conductors are to be sized for 35 amps which is #10 THHN in conduit or #8 NM-b.
Kevin54
MEMBER EMERITUS
When I go back out to the garage today, I'll double check and snap a pic or two. I'm almost positive that it is #12 wire. The reason I say that is I had another piece that I was going to use that was on my lathe, but it was too short when I moved the lathe. And when I wired everything I ran #10 wire and also bought a length of #10 bus drop which is considerably larger than what I had.
So I know my lathe was ran with #12. I am positive of that. And I am not sure now about the air compressor, but I think it is the same bus drop used that was used on the lathe.
And I don't doubt that the guy that wired it knows what he's doing as the maintenance guys at work have to go back to school and take test constantly to stay on top of things.
I'll check it here in an hour or so and let you know for sure.
So I know my lathe was ran with #12. I am positive of that. And I am not sure now about the air compressor, but I think it is the same bus drop used that was used on the lathe.
And I don't doubt that the guy that wired it knows what he's doing as the maintenance guys at work have to go back to school and take test constantly to stay on top of things.
I'll check it here in an hour or so and let you know for sure.
I called my friend yesterday and he's the electrical inspector for a City of 50,000 people. I told him of my situation of only one space left in my box and needing two spaces. He suggested taking two lightly loaded circuits and tying them together in the panel and running a short piece of the same size wire to one breaker thereby freeing up the additional space that I needed. Then purchase a 30 amp 240 volt breaker and wiring #10 thhn wire in flex conduit to the motor about 8-10' from the panel.
sberry
Banned
I only glanced at the specs but what is the difference in the 2 Quincy models, both 2 stage, both 5 hp and one lists 21A and the other 28?
Kevin54
MEMBER EMERITUS
I can't get a good picture unless I ink it in as it's molded into the cable, but I am running 12/3 Bus-drop cable to my compressor. And again, it was wired by a certified electrician. And it's wired to a 30 amp circuit.
Aceman
Well-known member
It doesn't matter who wired it, certified or not, it's still technically not legal.
Do I think it's going to melt down? Maybe, maybe not.
Would I ever install something like this for a paying customer when I know it's not right? Absolutely not.
sberry
Banned
Northern has 2 different models of quincy and lists the specs, both 2 stage and listed at 5 hp. One with run of 21 and one with 28 and it seems the cfm was 15 and 19. 20% difference. The price was 1400 and 2K I think. Obviously one really is 5 hp and one 3.2 but list it as 5.
wyliesdiesels
Well-known member
Inrush is 4x-8x FLC so 28a would be too low for inrush amps!
^ +1! I see hack work done by licensed guys all the time!
Theres different types of wire so its not that simple! The figures u listed are for NM-b wire. THHN wire, as an example, has a higher ampacity.
And your right. In a motor circuit, the breaker does not protect the wire. That is the job of the overloads!
Kevin54
MEMBER EMERITUS
I sent an e-mail to my buddy at work to see what drops are on the mills and lathes there. If I should have #10 busdrop, then I will change it out, no problem there. I know when I moved my machines, I wired #10, and when I ran the wire for the 220 outlets, I ran #10. And I know I ran #10 down from the breaker panel to the outlet, but the electrician that hooked everything up ran a #12 busdrop to the compressor. I'll see if I can find the book on the compressor. If it calls for #10, and you guys say #10, then by God, I'll go get some #10. The last thing I want is for the garage to burn down.
Aceman
Well-known member
I will tell you the easiest way to verify whether it really needs larger wire or not.
Read the nameplate on the motor, if it says 5HP, you need larger wire.
If it says SPL or some other abbreviation instead of the actual HP, then tell us what the motor amps are.
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sberry
Banned
http://www.northerntool.com/shop/to...-air-compressors+19-cfm-below-air-compressors Here is what I mean, both 5 hp It looks by the pic one has a starter.
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Major Ramifications
Well-known member
I think we need to focus on the rated current draw of the motor and not the claimed HP.
The reason I say this is that the motor plate may have SPL listed under HP, but the compressor manufacturer calls theirs a 5HP model to compete with all the other 5HP models out there.
What is the current draw listed on the motor plate?
Some "5HP" compressors draw less than 15 amps.
The reason I say this is that the motor plate may have SPL listed under HP, but the compressor manufacturer calls theirs a 5HP model to compete with all the other 5HP models out there.
What is the current draw listed on the motor plate?
Some "5HP" compressors draw less than 15 amps.
Kevin54
MEMBER EMERITUS
I wanted to bump this back up to the top and just say......My electrician wired my compressor wrong!!!! It's wires with #12 wire, and I had no reason to really doubt him as he is certified and wires machinery up at work all of the time.
BUT.....after listening to the replies on here, I dug around in every place I could think of to find the book on my compressor. BTW.....Menards pamphlet holder in the lid of their toolboxes, can hide a manual.
And sure enough it calls for No.10 wire. I sort of forgot about it until I was cleaning the garage the other day. So I will be swapping that wire out. And I want to thank everyone for pointing it out. Next time that I have something similar wired that I'm not familiar with, I'll ask here first before I get a local electricians idea on things 
BUT.....after listening to the replies on here, I dug around in every place I could think of to find the book on my compressor. BTW.....Menards pamphlet holder in the lid of their toolboxes, can hide a manual.
And sure enough it calls for No.10 wire. I sort of forgot about it until I was cleaning the garage the other day. So I will be swapping that wire out. And I want to thank everyone for pointing it out. Next time that I have something similar wired that I'm not familiar with, I'll ask here first before I get a local electricians idea on things Mr onetwo
Well-known member
I have rebuilt a couple of 5 HP motors, a Dayton which draws 20.8 FLA and a huge industrial Baldor that draws 26.9 running an IR compressor.Baldor lists the starting amps (inrush currant) for my motor as 157. That is why you have to use motor rated components and wiring sizes.I think the difference in FLA might be due to running torque ratings.
Gary S
Well-known member
That's how I did mine. I hardwired it to the panel with a short piece of flex and #8 wire. For mine, #10 would have been enough, but I always go one size over what a motor needs for faster starts that seem to help motor life.
57JoeFoMoPar
Well-known member
OK, I don't mean to hi-jack this thread, but I have a couple questions that might pertain to the OP.
Disregarding labeled motor HP rating, and using only start and run amperage as listed on the motor plate, if the start-up amperage doesn't exceed 30 amps, then the compressor could then be wired with a two-pole, 30 A breaker correct? Or should the continuous draw of the motor not exceed 60% of the breaker's capacity? Therefore, if the running amps were approximately 22A at 220v, there should be a 40A breaker and 8 gauge wire? Or would 10 gauge THHN wire and a 30A breaker be sufficient and up to code?
The compressor I'd be looking to install would be this one: http://www.homedepot.com/p/Husky-80...page_rr-3-_-NA-_-203187346-_-N#specifications
Also, as far as receptacles go, why is the receptacle rated at fewer amps than then circuit? Would it not be acceptable or to code to wire a compressor to a 30A or 50A plug and receptacle like these? It would be nice if the machine could be unplugged and moved.
http://www.mcmaster.com/#nema-connectors/=pzaeh9
Disregarding labeled motor HP rating, and using only start and run amperage as listed on the motor plate, if the start-up amperage doesn't exceed 30 amps, then the compressor could then be wired with a two-pole, 30 A breaker correct? Or should the continuous draw of the motor not exceed 60% of the breaker's capacity? Therefore, if the running amps were approximately 22A at 220v, there should be a 40A breaker and 8 gauge wire? Or would 10 gauge THHN wire and a 30A breaker be sufficient and up to code?
The compressor I'd be looking to install would be this one: http://www.homedepot.com/p/Husky-80...page_rr-3-_-NA-_-203187346-_-N#specifications
Also, as far as receptacles go, why is the receptacle rated at fewer amps than then circuit? Would it not be acceptable or to code to wire a compressor to a 30A or 50A plug and receptacle like these? It would be nice if the machine could be unplugged and moved.
http://www.mcmaster.com/#nema-connectors/=pzaeh9
460Rustang
Well-known member
Compressor wiring threads are always so interesting,... 
Charles (in GA)
Well-known member
The 80% rule (not 60%) generally applies to continuous loads, ie. 3 hrs or more by def in the code. Motors should also be wired to 125% of nameplate amperage, and the breaker can be as large as 250% of the FLC (Full Load Current) as listed on the motor name plate, to prevent it from tripping.
I would wire the compressor you link to above, 22 amps, with 10 gauge wire, and install a 30 amp breaker. If you have problems with it tripping, then I'd swap the breaker to a 40 amp. Breakers are cheap and easy to swap.
Charles
Highlux
Well-known member
Hard wired 220 with a relay to a rated switc on the garage wall. Compressor in basement.
Cant stand to hear them run.
Cant stand to hear them run.
Robert Hall
Well-known member
Compressor in shed with 10-3 on a 50 amp 220 single phase.
Junkman
Well-known member
My vertical compressor is on wheels, so I have a 10 gauge cord with a L6-30 plug on the end of it. I plug it into a matching receptacle that is wired with 10 gauge wire. Is this OK or not? my two 30 amp outlets are wired with 10 gauge wire, and each has its own dedicated circuit breaker.
wyliesdiesels
Well-known member
The reason motor circuits are wired based on HP is because some motors have a higher FLA than others in the same HP rating. If u have a 5hp motor that has an FLA of 22a and u replace it with another 5HP with an FLA of 28a(which is the NEC table FLC) then the circuit wont have to be rewired to accomadate the higher FLC because the corcuit was wired for a 5hp motor.
As far as outlets go, standard 30a and 50a nema outlets have a max rating of 3hp. U can get an outlet rated for higher HP but theyre crazy expensive!
Compressor in shed with 10-3 on a 50 amp 220 single phase.
If thats cordage, then thats not to code as it doesnt have a high enough ampacity!
What is the size of your compressor? If larger than 3hp, then it should be hard wired as its not upto code since the outlets arent rated for more than 3hp!
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or black.
Junkman
Well-known member
It is a 5 HP Quincy 2 stage compressor. I have been operating it this way for over 10 years now. In the past, I never thought of it as being "wrong", but I now know. It was originally hard wired with 12 gauge romex, but when I expanded the garage, I needed to get it out of the way, and this was the best solution at the time. I will look into a more permanent location for it in the spring.
I also have the same set up for the 4 post lift, but that is only a 2 HP motor, so I assume that is OK??