compressor and welder wiring

[jpcjguy]

Hi all,

So I am ready to wire outlets/boxes for my compressor and welder.
Welder is a millermatic 252 (older model)
Compressor is a home depot 60 gallon.
I have attached pics of models, motor plate, info from manuals

As for wire size, from an online manual I could find, I can use 10 gauge for the compressor (run to that location is about 50ft). There is no breaker size mentioned.

The run for the welder outlet location is about 45ft. Current model 252 manual states min. 8 gauge
Isn't 8 gauge only rated for 40A? I am assuming they are taking into consideration duty cycle of the welder? Should I step to 6 gauge?

So in terms of wire sizing, the compressor is a "light duty" model I got a long time ago. I am on the lookout for a better two stage 60 gallon if a good deal comes around so I would like to somewhat future proof for a larger compressor.
As you can see my wiring needs hover right around 90-100 feet. Looking at 6 and 8 gauge rolls at Lowes, they come in 50 or 125ft rolls. 125ft roll would be ideal *if* I can use the same gauge for both circuits - taking into account slack and stapling etc. (to be safe)

Would 8 gauge work for the welder outlet and then also run it for the compressor outlet? Would that give me some protection to a larger compressor down the road?
Trying to be practical in wire spending - but want to take into account breaker size, wire actually fitting in the breaker (i don't think 6 gauge would fit in a 30A or smaller breaker for the compressor), etc.

Thoughts?

 

[Zeke]

Plan on 240v for the compressor if you're thinking of an upgrade. That will throw your wiring yield out the window.

Many supply houses and online sellers sell by the foot. Order what you need.

 

[jpcjguy]

compressor is 240v currently, just thinking 10 gauge will not support a larger compressor/motor so should I step to 8 gauge?
Edit: just found this thread: https://www.garagejournal.com/forum/showthread.php?t=353669
and a larger compressor (from what I have) like the Quincy QT-54 appears to be recommended to use 8/2 for my 50ish foot run.

 

[wyliesdiesels]

Motor circuits are not wired based on gallon size. Not sure why people always list gallon size to determine circuit size. Gallons mean nothing when it comes to wiring for a motor.

What you need to size the wire for a motor is the HP rating. Your motor appears to be about 3HP since it has an FLA of 15a.

If you want a 5HP motor you will need #10 in pipe or #8/2 NM-b

The welder circuit is sized by input current and duty cycle.

 

[jpcjguy]

Motor circuits are not wired based on gallon size. Not sure why people always list gallon size to determine circuit size. Gallons mean nothing when it comes to wiring for a motor.

What you need to size the wire for a motor is the HP rating. Your motor appears to be about 3HP since it has an FLA of 15a.

If you want a 5HP motor you will need #10 in pipe or #8/2 NM-b

The welder circuit is sized by input current and duty cycle.

Thanks for the info - regarding the gallon size, that was just a reference of the general size of the compressor I would use. When I said "plan for a larger compressor", I did not want to give the impression I was going to step up to some 200+ gallon monster for a full size industrial shop.
So it appears the "larger" compressor in the 60-80 gallon size is about a 5HP 7.5HP motor. So if I found a deal on a 7.5HP, then #6 wire would be needed right?

 

[sberry]

5 needs 8, 7.5 needs 6. These are for cable. The welder calls for 6 cable too, a 252 is the heaviest machine that comes factory cord and plug. But,,,,,,, if I was doing this would do it all 8 if I thought I was going to change comps. None of this would cause me sleep loss no matter what I put on it.
In particular here the welder. While it does call for 8 pipe or 6 cable it won't overheat a 10 at home, won't even warm it. It's a 60% duty machine at its rated output, it will push 300 but a guy would have to change the gas, the wire and the gun that comes with it. It would melt the factory gun to a cinder before it overheated a wire. It needs a 50 breaker, it's not a problem for 8 on a welder or comp circuit.

 

[jpcjguy]

5 needs 8, 7.5 needs 6. These are for cable. The welder calls for 6 cable too, a 252 is the heaviest machine that comes factory cord and plug. But,,,,,,, if I was doing this would do it all 8 if I thought I was going to change comps. None of this would cause me sleep loss no matter what I put on it.
In particular here the welder. While it does call for 8 pipe or 6 cable it won't overheat a 10 at home, won't even warm it. It's a 60% duty machine at its rated output, it will push 300 but a guy would have to change the gas, the wire and the gun that comes with it. It would melt the factory gun to a cinder before it overheated a wire. It needs a 50 breaker, it's not a problem for 8 on a welder or comp circuit.

Thanks - Doing all 8 sounds like a plan and I will check it with my AHJ. Gives me flex for a larger compressor and I don't ever see myself maxing out that 252 - heck I only use it a couple times a year (but that is because I don't have the space right now)

 

[sberry]

I use 10 extension cord when I do use one. I have burned on the 250, cant feel it warming. As for space and using it, while it may be a factor the type of work is where it matters. Building logging truck or dump truck beds, places a guy could really hold down that long. On hobby/home,,, never.

 

[matt_i]

I would recommend running either EMT or PVC-rigid conduits.

Then you can pull stranded conductors which are smaller dia, are tougher on the outside, and resistant to oil, gas, water. And you can easily buy by-the-foot and not stress over rolls or multi-dollar-per-foot NM cable. You have the finished wireway as an easy measuring guide.

And you are immediately future proofed if you have enough diameter. Look at it as a wireway that can also be used for future needs...simply add length and pull in more wires.

 

[Bert_]

I would recommend running either EMT or PVC-rigid conduits.

Then you can pull stranded conductors which are smaller dia, are tougher on the outside, and resistant to oil, gas, water. And you can easily buy by-the-foot and not stress over rolls or multi-dollar-per-foot NM cable. You have the finished wireway as an easy measuring guide.

And you are immediately future proofed if you have enough diameter. Look at it as a wireway that can also be used for future needs...simply add length and pull in more wires.

Stranded wire is not smaller diameter. It's actually bigger than solid wire.

The wire inside NM cable is THHN so no advantage there. The only downside is that NM is limited to 60* ampacity even though it does contain THHN.

 

[sberry]

The codes are for a reason. This is an area there is a lot of room for error. Aint no one ever burned the shack down with a modern 5 comp on a 10 cable with a 30 breaker, millions of these type hookups in service for decades wired wrong. Saw a 7.5 run regular for 20 years on a 12.

 

[sberry]

These are 2 things that if I can help it get their own pipe if I am going to pipe my own work.

 

[jpcjguy]

sigh....my inspector wants to see 6 gauge for the welder outlet if I use a 50A breaker. I guess it is what it is.....
at least I can get it by the foot at the local electrical supply - that wire should only cost me about $60 for the 45ft run. and about $50 for the 55ft run of 8 gauge for the compressor.

 

[wyliesdiesels]

sigh....my inspector wants to see 6 gauge for the welder outlet if I use a 50A breaker. I guess it is what it is.....
at least I can get it by the foot at the local electrical supply - that wire should only cost me about $60 for the 45ft run. and about $50 for the 55ft run of 8 gauge for the compressor.

show him the code reference for welder circuits

https://www.ecmweb.com/national-electrical-code/qa/article/20889547/code-qa

 

[sberry]

You can run a legal 10 cable 50A welder circuit.

 

[TractorJeff]

You guys always say don't argue with the AHJ?
I bet his reasoning is - "Well you won't live here forever and the next person will turn this into a Party Garage and plug an Oven in the outlet" or the Newest is "Next Owner will plug his EV into the outlet"

 

[Tekan1]

Thanks for the details in this thread. Very good information for I too am hooking up a welder and compressor.

 

[Bert_]

You guys always say don't argue with the AHJ?
I bet his reasoning is - "Well you won't live here forever and the next person will turn this into a Party Garage and plug an Oven in the outlet" or the Newest is "Next Owner will plug his EV into the outlet"

In all reality this isn't the inspectors decision. He doesn't make codes.

If you don't want to argue with the guy just run the #8 Romex like you were planning and put it on a 40A breaker. Change to a 50 when he leaves.

 

[wyliesdiesels]

You guys always say don't argue with the AHJ?
I bet his reasoning is - "Well you won't live here forever and the next person will turn this into a Party Garage and plug an Oven in the outlet" or the Newest is "Next Owner will plug his EV into the outlet"

The inspector is NOT the AHJ. He is a representative of the AHJ. Many times inspectors get overruled and written up for trying to enforce things that are not code.

Also, code is not for “what if’s” and the inspector isnt there to make the codes, he’s there to enforce them.

BTW, How does one plug a 120/240v 4-wire grounded oven into a 240v 3-wire grounded outlet?