220 Air Compressor Amp Question.

[pattenp]

Since you mentioned the outlet being 2ft away are you thinking of using that circuit for the hardwire plus the outlet? The compressor when hardwired should be on its own dedicated circuit. Without reading back through all the post did you say what size and kind of wire is used for the existing outlet? Is the existing circuit wire #6 NM?

 

[JOE.G]

Right next to teh Compressor I have a 50 Amp 220 circuit and a 20 Amp Circuit, the 20 Amp one as 12 AWG Romex with what looks like a double 20 amp breaker on it. The 50 Amp Circuit has 6 AWG Wire.

 

[RickP]

Hey there Joe, sorry about all the confusion. I feel your pain as I am going through the same thing, using temporary wiring for 6-12 months, and then switching to a permanent solution later. Mine is also a 5 hp motor.

I finally decided that the cheapest/best/safest option for the temp connection was a 10 AWG A/C Whip wired to a knockout in the junction box for my 50 amp welding outlet. Total cost: $11. I just used the switch on the compressor to turn it on and off, rather than having a disconnect, but my sub-panel is only two feet away. That A/C whip will come pre-wired with THHN/THWN that will handle 35A, enough for a 5 hp motor.

If you want to use the 6-50 plug temporarily, go for it. It doesn't meet code, but it will probably work. I used mine for 2 months that way - with a 6-50P and the A/C whip. Of course that plug was designed for cord, but I just took out the cable clamp and it fit perfectly with the conduit fitting on the A/C whip. Your 10 AWG cord is a little undersized, according to the NEC, but again, it will probably work, especially if you unplug it when you're finished working. If you wanted to switch it to 8 AWG cord, you could do that, but the A/C whip would probably be cheaper for a temporary solution.

Good luck with it -- and just get it done so you can move on to better things!

 

[JOE.G]

I have the Compressor running off the 20 Amp circuit now, How could I hook it up so I could still have a outlet there for the welder? COuld I hook some kinda J Box up?

 

[RickP]

Yes, you can wire the outlet and the compressor into the same circuit using a j-box (or two). Just make sure to turn off the compressor before you fire up the welder. This is only temporary, right? Maybe 6 months or so? This is completely safe, it's just not how you wanted it to be permanently installed.

I would buy some 8 AWG THHN -- two feet would probably do it. I'm assuming your current j-box is 4x4, so you'd need another one of those with a blank cover plate. Mount the two j-boxes next to each other with the knockouts connected. Move the existing 50A outlet to the new j-box, and use the existing j-box for the A/C whip (post #67) with the cover plate. You'll need some big wirenuts (post #96).

In the existing j-box, you connect the incoming cable to the A/C whip and a pigtail. The pigtail goes to the other j-box and connects to the outlet. Like this, only bigger:

 

[RickP]

Joe -- I thought I'd add a note about the wire sizes. I recommended 8 AWG THHN because that's the biggest wire that would fit in that wirenut with the 6 AWG feed wire and the 10 AWG A/C whip. According to pattenp (post #29) the 8 AWG THHN can handle 50 amps in conduit. I'm not exactly sure how to hook those two j-boxes together and protect the sharp edges of the knockout holes, but the hardware store should have some kind of plastic ring that would snap into them. I think you can attach the two j-boxes together without using conduit, as long as it's temporary.

PDF: Ideal 454 wirenut allows 1-#6 with 1-#8 with 1-#10.

 

[JOE.G]

The 6-50 Plug should be good for the Welder Correct? Mig Arc or Tig?

 

[RickP]

That's the plug that came with my welder. Mine is a stick welder, but I think Mig/Tig should use the same plug. I think that's a pretty standard plug for a welder.

 

[JOE.G]

Ok Guys lets see if I am right,

I have 6 AWG 4 Wire going from 50 Amp breaker to the Outlet, Color is 1 Red,black,white and a bare, the red and black go to the breaker, the white to the Neutral bar and the Bare to the ground bar. At the outlet there is only 3 spots for wire, I have the Red and the Black going to the to Flat Prongs which are the hots, Now I have the White going to the circle ground prong and the bare to the metal Outlet box.

Should I cap the white/Neutral instead and unscrew the Bare ground from the box and put that into the ground spot on the outlet? Or is it ok to leave the WHite hooked up, I don't think the Ground bar and the Neutral bar are connected in the panel box, and the neutral bar has plastic feet on it so It isn't grounded to the box.

Also does it mater which of the hots go to which side of the Outlet?

 

[pattenp]

The bare goes to the ground prong. The white goes unused.

 

[JOE.G]

Ok, Guys sorry for all the questions, I am just real nervous with Elec, Any big Project I would have a Elec pro do, But this is something I know I can do just want to make sure it's right.

I Got Number 6 AWG Cord, I hooked the 6-50 Plug to it and wired it to the Compressor switch, I used the white and black for power and the green for ground, I had to trim some of the wire strands off to be able to hook it to the switch, I also put a Round wire connector on the green ground and crimped it and had it screwed to the switch box.

I Unhooked the White neutral in the elec box and Elec taped the heck out of it since I didn't have a bigger enough Wire nut. I hooked the bare ground to the ground spot on the Outlet where the Neutral was.

I left the Neutral hooked up at the breaker box. Sound right? The 6 AWG Wire is pretty thick.

 

[pattenp]

If the outlet box is metal it needs to be also hooked to the bare ground wire. Usually you take the bare ground to the box then jump to the outlet. Back to your previous post if the source panel is the main panel then the neutral bar and ground bar should be bonded. There should be a grounding jumper strap or screw from the neutral bar to the case.

 

[JOE.G]

Man Now I am geting more confused, The ground wire is to the outlet and not the box, but the metal case/outlet is screwed to the box so would that ground it?

The panel in the shop isw a sub panel fed from my home, It isn't bonded I don't think, I have two ground rods going to the ground bar, It passed Inspection this way.

 

[pattenp]

Unless the outlet is listed as self grounding you need to ground the box with the ground wire if the box is metal.

In post 129 if the panel you're talking about is a sub-panel then the neutral and ground are NOT to be bonded. The neutral should be isolated from the ground. In other words the neutral bar should not be connected to the panel or the ground bar. The only place the neutral and ground should be bonded is in your main service panel in the house.

The grounding rods are fine and required for the shop sub-panel if the shop is detached from the house.

Man Now I am geting more confused, The ground wire is to the outlet and not the box, but the metal case/outlet is screwed to the box so would that ground it?

The panel in the shop isw a sub panel fed from my home, It isn't bonded I don't think, I have two ground rods going to the ground bar, It passed Inspection this way.

 

[JOE.G]

Yes the house panel is bonded and the shop one is not, Now I need to add a wire I guess, Do I just Add it to outlet lug and then screw it to box? Does it matter what size wire?
The ground wire is touching the box now since I left it long and stuffed it in box.

What is the reason for this?

I am using a Levition 6-50 Outlet.

 

[wyliesdiesels]

Ok, Guys sorry for all the questions, I am just real nervous with Elec, Any big Project I would have a Elec pro do, But this is something I know I can do just want to make sure it's right.

I Got Number 6 AWG Cord, I hooked the 6-50 Plug to it and wired it to the Compressor switch, I used the white and black for power and the green for ground, I had to trim some of the wire strands off to be able to hook it to the switch, I also put a Round wire connector on the green ground and crimped it and had it screwed to the switch box.

I Unhooked the White neutral in the elec box and Elec taped the heck out of it since I didn't have a bigger enough Wire nut. I hooked the bare ground to the ground spot on the Outlet where the Neutral was.

I left the Neutral hooked up at the breaker box. Sound right? The 6 AWG Wire is pretty thick.

Bad idea to trim some of the wire off. U could have issues down the road. A better technique would be to use a short piece of building wire such as THHN as a pig tail to the switch. Also, if the crimp type connecters u used are the ones im thinking of, they are not code approved!

Yes the house panel is bonded and the shop one is not, Now I need to add a wire I guess, Do I just Add it to outlet lug and then screw it to box? Does it matter what size wire?
The ground wire is touching the box now since I left it long and stuffed it in box.

What is the reason for this?

I am using a Levition 6-50 Outlet.

The reason is so that the metal box is grounded in case a hot wire comes loose and energizes the box, conduit, metal in the building, etc. if it wasnt grounded and became energized, then a shock hazard exists.

As for the outlet, pattenp explained it: the yoke or chassis on many larger outlets are not self grounding meaning the yoke is not connected to the ground screw/pin on the outlet.

 

[JOE.G]

They look like what was in the switch from the factory that grounds the motor to the switch, I can't get the 6 AWG Wire into the switch unless I trimmed it a bit. The 10 AWG I have does fit fine, SHould I just use that cord? I am unsure WHy I can't if the Compressor only draws 28 Amps on start up,.

 

[pattenp]

You can use a short pigtail of #10.

The box needs to be grounded because there is a possibility of the mechanical connection of the outlet to the box not maintaining an effective ground fault current path. It's a NEC thing.

Yes the house panel is bonded and the shop one is not, Now I need to add a wire I guess, Do I just Add it to outlet lug and then screw it to box? Does it matter what size wire?
The ground wire is touching the box now since I left it long and stuffed it in box.

What is the reason for this?

I am using a Levition 6-50 Outlet.

 

[pattenp]

28A X 1.25 = 35A. This is why I suggested a #8 cord. I'm not going to tell you to use the #10, that's your call.

They look like what was in the switch from the factory that grounds the motor to the switch, I can't get the 6 AWG Wire into the switch unless I trimmed it a bit. The 10 AWG I have does fit fine, SHould I just use that cord? I am unsure WHy I can't if the Compressor only draws 28 Amps on start up,.

 

[JOE.G]

No Prob, I ll pick up a Section of Number 8 Cord this week. I hope to be able to fit them in better. I have scrap 12 AWG, Could I use that for the jumper? And All I do is screw in with the ground wire on the outlet then screw it to the box. Guys thanks again for taking the time to walk me though this, I know it is a no brain er for you guys.

Also is it safe to leave the 50 AMP Breaker in place?

 

[pattenp]

You should use a piece of #10 for the ground.

If the circuit is wired with #6 and the outlet is a 50A outlet then it's okay to have the 50A breaker. The breaker is for protecting the outlet circuit, not the cord and plugged in device beyond the outlet.

 

[JOE.G]

Patten that makes me feel a touch better about my Set Up, I'll grab some 8 Awg and try and see if that'll fit, I then will make a jumper with at least 10 Awg Wire. Last thing I want is for someone to get hurt because of bad wiring, Elec Makes me very nervous just in case you can't tell.

 

[JOE.G]

Well after all these years I finally hard wired it. I never had a issue with the cord ( it seems like it started slower but may be in my head ). I have the 50 amp plug there and wired it to a 60 a disconnect fused down to 30 amp.

 

[JOE.G]

I believe it's all to code, I wanted to keep the outlet so I did it this way, I use the disconnect as the on off switch now.

 

[sberry]

I am going to add to this cluster fug. We rate a 5 by hp,,, requires an 8 cable or 10 single conductor,, seems a lot of people are using the amp ra ting for 7 1/.2 in this thread instead of the hp chart. Takes 8 in pipe and 6 cable. Needs direct wire.
The comp has the potential to run 100%. A range does. They say an oven will reach temp and shut off, spose the door could be left open. Spose a water heater could run continious under duress. ???

 

[JOE.G]

Sberry you lost me Lol, Does my set up look correct? I used the correct 30 amp wire and from Compressor to disconnect and the correct 50 amp wire to outlet.

 

[wyliesdiesels]

Sberry you lost me Lol, Does my set up look correct? I used the correct 30 amp wire and from Compressor to disconnect and the correct 50 amp wire to outlet.

what he's saying is motor circuits are wired based on HP rating NOT ampacity rating. The breaker rating does not matter here.

A 5Hp motor needs #10 THWN in pipe or #8 NM-b.

What did you use?

 

[JOE.G]

I believe it was #10 to compressor and #6 to 50 amp outlet I'd have to double check.

 

[AllThingsOld]

And it doesn’t work. Everything is wired properly, not tripping the breaker, it’s definitely getting 120 on each side of the switch. I can hear the motor trying to start, but it doesn’t. Now when I flip the pressure switch on, I get nothing, no sound.. I want to pull my hair out

 

[wyliesdiesels]

wrong thread?

 

[Norcal]

And it doesn’t work. Everything is wired properly, not tripping the breaker, it’s definitely getting 120 on each side of the switch. I can hear the motor trying to start, but it doesn’t. Now when I flip the pressure switch on, I get nothing, no sound.. I want to pull my hair out

Are you getting 240V? You can read 120V on each leg & still not have 240V.