Welder- 240V

[American Locomotive]

...or just put on a plug 6-50 plug on it and call it a day, because it will be fine. Too many people take the code as gospel, when it has a ton of stupid things in it that are sort of inherently unsafe or don't make sense.

For example: It's not code to put a 5HP compressor on a 6-50R plug (even though it can handle the current perfectly fine) in the very slight off chance that someone yanks the plug while the compressor is running.

However, it's perfectly fine to have an unlabeled 6-50R outlet wired with 12 gauge wire attached to a 50A breaker for a welder. But when Joe-Blow gets chilly grinding some metal in the shop, he can unplug the welder, wheel this (https://www.amazon.com/dp/B09FX61B7G/?tag=atomicindus08-20) bad boy over and then immediately proceed to set my entire welding circuit on fire.

... or I replace my old AC-225 buzz-box with a 20% duty cycle with a shiny new Power Mig 360 with 60% duty cycle - and once again proceed to set my wires on fire because the previous owner of my shop wired this outlet with 12 gauge wire and never labeled the outlet as such.

 

[wyliesdiesels]

...or just put on a plug 6-50 plug on it and call it a day, because it will be fine. Too many people take the code as gospel, when it has a ton of stupid things in it that are sort of inherently unsafe or don't make sense.

For example: It's not code to put a 5HP compressor on a 6-50R plug (even though it can handle the current perfectly fine) in the very slight off chance that someone yanks the plug while the compressor is running.

However, it's perfectly fine to have an unlabeled 6-50R outlet wired with 12 gauge wire attached to a 50A breaker for a welder. But when Joe-Blow gets chilly grinding some metal in the shop, he can unplug the welder, wheel this (https://www.amazon.com/dp/B09FX61B7G/?tag=atomicindus08-20) bad boy over and then immediately proceed to set my entire welding circuit on fire.

... or I replace my old AC-225 buzz-box with a 20% duty cycle with a shiny new Power Mig 360 with 60% duty cycle - and once again proceed to set my wires on fire because the previous owner of my shop wired this outlet with 12 gauge wire and never labeled the outlet as such.

the very slight off chance?

lol

ive seen people yank compressor plugs out of receptacle that werent rated for them and then they got a huge arc flash

never under estimate peoples' stupidity....

 

[Aroberson77]

Wiring for a compressor is a different animal than a welder, just to reiterate what's been said here.

Running a welder on the 40a circuit with #8 is almost certainly not a problem, but if you sized the welder circuit's wire to align with what code allows, you would not be able to run a big compressor on it.

Also me careful with that compressor on a plug. Plugs need to be rated for the HP of the motor and a regular 50a plug is only rated for up to 3hp

Thank you guys for that info. I incorrectly assumed that the compressor was going to pull less amps than my welder

 

[mike93lx]

Thank you guys for that info. I incorrectly assumed that the compressor was going to pull less amps than my welder

I would get that compressor switched over to hard wired and use an extension cord for the welder instead.

 

[Aroberson77]

I would get that compressor switched over to hard wired and use an extension cord for the welder instead.

I am actually still working on the compressor wiring, welder circuit is done. I definitely will be rereading the install manual and motor nameplate

 

[American Locomotive]

Thank you guys for that info. I incorrectly assumed that the compressor was going to pull less amps than my welder

It has nothing to do with the amps. A 6-50R outlet can supply enough current for a 7.5 or even 10HP motor. The issue is when the power is suddenly turned off to a big motor, an arc can be created. The switch or contactor inside the compressor's controller is designed to extinguish the arc or prevent it from happening. The 50A 6-50R outlet is not designed to prevent arcs when being disconnected. You could get an arc flash if you unplug the compressor while running. But it's perfectly fine and safe while plugged in.

ive seen people yank compressor plugs out of receptacle that werent rated for them and then they got a huge arc flash

never under estimated peoples stupidity....

...and I have never seen anyone unplug a running 5-7.5HP compressor on a 6-50R, but on the other hand I've seen A LOT of people plug various things into 6-50R outlets without any concern at all for the size of the supplying wire.

My point is, the NEC is not the end-all of safety. The "welder wire-sizing rule" is an inherently unsafe rule. It relies purely on the installer/owner of a facility REMEMBERING that a particular 50A breaker/receptacle combo has undersized wire and is only suitable for welders. That context is lost the moment the installer/owner is gone for a while, forgets, dies, puts someone else in charge, sells the building, whatever.

Your response to that was simply "that's the next guy's problem" followed by a poor argument about the sizing of a building's framing. A building is not typically not designed to be changed or have a second floor added after-the-fact. On the other hand, a receptacle is inherently designed to have different devices plugged into it. A welder can easily be upgraded sometime down the road (or the new owner of a building plugs in a larger welder), another piece of equipment (heater, drum sander, whatever) plugged in if it's the closest and most convenient outlet, whatever.

Here's a more apt comparison: A company installing a 10,000 lb car lift on a floor that can only handle 1,000 pounds, because they only intend to use the lift to service golf carts. Someone else buys the building (or uses the shop outside of normal hours), sees a 10,000 pound lift, puts their truck on it, and then the whole thing goes crashing through the floor. That's the equivalent of putting a 50A breaker and a 50A outlet on 12 gauge wire and then saying "only use it for welders please".

...and FYI, I've seen a lot of commercial air conditioning equipment with cooked power feed wires due to the NEC allowing oversized breakers on undersized wires for air conditioning and motor loads. It relies purely on the overload protection inside the equipment to provide safety, even though I've seen tons of motor starters weld themselves closed rendering the overload heaters useless.

 

[wyliesdiesels]

It has nothing to do with the amps. A 6-50R outlet can supply enough current for a 7.5 or even 10HP motor. The issue is when the power is suddenly turned off to a big motor, an arc can be created. The switch or contactor inside the compressor's controller is designed to extinguish the arc or prevent it from happening. The 50A 6-50R outlet is not designed to prevent arcs when being disconnected. You could get an arc flash if you unplug the compressor while running. But it's perfectly fine and safe while plugged in.

...and I have never seen anyone unplug a running 5-7.5HP compressor on a 6-50R, but on the other hand I've seen A LOT of people plug various things into 6-50R outlets without any concern at all for the size of the supplying wire.

My point is, the NEC is not the end-all of safety. The "welder wire-sizing rule" is an inherently unsafe rule. It relies purely on the installer/owner of a facility REMEMBERING that a particular 50A breaker/receptacle combo has undersized wire and is only suitable for welders. That context is lost the moment the installer/owner is gone for a while, forgets, dies, puts someone else in charge, sells the building, whatever.

Your response to that was simply "that's the next guy's problem" followed by a poor argument about the sizing of a building's framing. A building is not typically not designed to be changed or have a second floor added after-the-fact. On the other hand, a receptacle is inherently designed to have different devices plugged into it. A welder can easily be upgraded sometime down the road (or the new owner of a building plugs in a larger welder), another piece of equipment (heater, drum sander, whatever) plugged in if it's the closest and most convenient outlet, whatever.

Here's a more apt comparison: A company installing a 10,000 lb car lift on a floor that can only handle 1,000 pounds, because they only intend to use the lift to service golf carts. Someone else buys the building (or uses the shop outside of normal hours), sees a 10,000 pound lift, puts their truck on it, and then the whole thing goes crashing through the floor. That's the equivalent of putting a 50A breaker and a 50A outlet on 12 gauge wire and then saying "only use it for welders please".

...and FYI, I've seen a lot of commercial air conditioning equipment with cooked power feed wires due to the NEC allowing oversized breakers on undersized wires for air conditioning and motor loads. It relies purely on the overload protection inside the equipment to provide safety, even though I've seen tons of motor starters weld themselves closed rendering the overload heaters useless.

umm what? where did i say anything in this thread about framing? you mustve tagged the wrong person

 

[wyliesdiesels]

My point is, the NEC is not the end-all of safety. The "welder wire-sizing rule" is an inherently unsafe rule. It relies purely on the installer/owner of a facility REMEMBERING that a particular 50A breaker/receptacle combo has undersized wire and is only suitable for welders. That context is lost the moment the installer/owner is gone for a while, forgets, dies, puts someone else in charge, sells the building, whatever.

Your response to that was simply "that's the next guy's problem" followed by a poor argument about the sizing of a building's framing. A building is not typically not designed to be changed or have a second floor added after-the-fact. On the other hand, a receptacle is inherently designed to have different devices plugged into it. A welder can easily be upgraded sometime down the road (or the new owner of a building plugs in a larger welder), another piece of equipment (heater, drum sander, whatever) plugged in if it's the closest and most convenient outlet, whatever.

umm so you think the goal of code is to worry about what someone does with it down the road? thats not how this works.

...and FYI, I've seen a lot of commercial air conditioning equipment with cooked power feed wires due to the NEC allowing oversized breakers on undersized wires for air conditioning and motor loads.

I guess youve never heard of nuisance tripping which happens because of in-rush current. THAT is the reason why the NEC allows for the breaker sizing for motors the way they do. If you size a breaker to the wire size on a motor circuit, you can have nuisance tripping. have fun with that.

It relies purely on the overload protection inside the equipment to provide safety, even though I've seen tons of motor starters weld themselves closed rendering the overload heaters useless.

you know why they welded themselves closed? because they got pitted and no one bothered with the maintenance of checking them and changing them out.

 

[American Locomotive]

umm so you think the goal of code is to worry about what someone does with it down the road? thats not how this works.

Why do I need to put 12 gauge wire on my 20A breaker for the outlets around my house when I only have a radio and a small window air conditioner? 16 gauge would be more than sufficient for the current. Why do I need to run 14 gauge wire on the 15A breaker for the lighting circuits in my house? I am only ever go to put LEDs in them, so realistically I should be able to use 18 AWG in conduit.

We don't do that because someone could plug a high-load device in. Someone could take my LEDs out and replace them with incandescent. The same thing could happen here with a 6-50R on a 50A breaker run with 12 gauge wire.

The NFPA's mission is to eliminate death, injury, property and economic loss from fire, electrical and other hazards. Not "let someone else other than the original installer die from an electrical fire".

I guess youve never heard of nuisance tripping which happens because of in-rush current. THAT is the reason why the NEC allows for the breaker sizing for motors the way they do. If you size a breaker to the wire size on a motor circuit, you can have nuisance tripping. have fun with that.

I'm well aware of why the NEC allows this. They do it to avoid nuisance tripping under the assumption the overload protection in the equipment will save the wires. Except in my experience, the overload protection in the equipment can often fail (depending on how it's implemented.)

My argument is that the wire should ALWAYS be sized to the breaker. If your motor needs a 60A breaker to not trip on start up, then your wiring should also be sized properly to match a 60A breaker. It's that simple.

you know why they welded themselves closed? because they got pitted and no one bothered with the maintenance of checking them and changing them out.

Whether or not the wires in my building burn should not be dependent on some random underpaid HVAC tech making sure the contactors are in good shape during his quarterly filter & belt changes. An electrical system should be inherently safe from fire - e.g. the wires should be able to bare the full rated current of the breaker regardless of what happens on the load side. Contactors, overloads, etc.. fail stuck-on all the time. Breakers rarely fail stuck on.

umm what? where did i say anything in this thread about framing? you mustve tagged the wrong person

 

[wyliesdiesels]

when i said joists i was referring to beams such as steal supporting a second floor not stick FRAMING like for a wall. tomatoes tomatos...

 

[wyliesdiesels]

Why do I need to put 12 gauge wire on my 20A breaker for the outlets around my house when I only have a radio and a small window air conditioner? 16 gauge would be more than sufficient for the current. Why do I need to run 14 gauge wire on the 15A breaker for the lighting circuits in my house? I am only ever go to put LEDs in them, so realistically I should be able to use 18 AWG in conduit.

We don't do that because someone could plug a high-load device in. Someone could take my LEDs out and replace them with incandescent. The same thing could happen here with a 6-50R on a 50A breaker run with 12 gauge wire.

The NFPA's mission is to eliminate death, injury, property and economic loss from fire, electrical and other hazards. Not "let someone else other than the original installer die from an electrical fire".

I'm well aware of why the NEC allows this. They do it to avoid nuisance tripping under the assumption the overload protection in the equipment will save the wires. Except in my experience, the overload protection in the equipment can often fail (depending on how it's implemented.)

My argument is that the wire should ALWAYS be sized to the breaker. If your motor needs a 60A breaker to not trip on start up, then your wiring should also be sized properly to match a 60A breaker. It's that simple.

Whether or not the wires in my building burn should not be dependent on some random underpaid HVAC tech making sure the contactors are in good shape during his quarterly filter & belt changes. An electrical system should be inherently safe from fire - e.g. the wires should be able to bare the full rated current of the breaker regardless of what happens on the load side. Contactors, overloads, etc.. fail stuck-on all the time. Breakers rarely fail stuck on.

so give me examples of buildings that burned down because of a wire/breaker combination for a motor circuit, that allowed the wire to burn and ignite the building on fire.

BTW the trip curve for breakers for an overload are higher than the allowable ampacity so...

 

[American Locomotive]

when i said joists i was referring to beams such as steal supporting a second floor not stick FRAMING like for a wall. tomatoes tomatos...

"Framing" is a colloquial term that means the "structure of a building". e.g., "Steel Framed Building", "Timber Framed Building". Regardless, you're just deflecting from the fact that your comparison wasn't good.

so give me examples of buildings that burned down because of a wire/breaker combination for a motor circuit, that allowed the wire to burn and ignite the building on fire.

I've already stated I've seen RTUs (and other equipment) with crispy or charred/burned supply wiring that needed to be replaced, usually caused by a fault within the equipment that prevented the equipment's thermal overload from functioning. If that were nm-b buried in a wall, and not wires in a conduit - it probably would have been a fire.

BTW the trip curve for breakers for an overload are higher than the allowable ampacity so...

The trip curve of a breaker has a carefully calibrated time-constant directly related to wire ampacity. The trip curves are designed to allow for temporary overloads without tripping. This is allowed because a wire will have thermal mass that needs to heat up, and natural thermal conduction/convection removing heat from the wire.

The key word being temporary.

A 20A breaker will allow a very temporary (typically 10-25 seconds) 45A overload on 12 gauge wire. On the other hand, a 50A breaker with 12 gauge wire and a 6-50R outlet, will in perpetuity flow 45A into that ~10KW portable space heater someone plugged into the outlet after they unplugged the welder. If that wire is a 150 foot run between the panel and the outlet, it will be disappointing nearly 1KW of heat. Just in the wire.

That is why I think putting undersized wire on a "welding outlet" circuit is bad practice - ESPECIALLY with the outlet unlabeled. You have no idea what someone might plug in there in the future, and you have no idea what kind of welding machine you might eventually upgrade to. Buy once, cry once. Put the right size wire in for the breaker.