Welding receptacles

[ZinskI/E]

What criteria are used when sizing a generic 3 phase, 480V welding receptacle in an industrial plant? After reading NEC article 630, I think I understand the requirements for sizing the conductors and OCP for welders using known values of the welding equipment, but I am unsure of how the design of a circuit for "welding receptacle" is reached when none of the specifics are known about the type of equipment that may be utilizing these receptacles.

My questions are: what dictates sizing of conductors and OCP of a welding receptacle if the specifics are unknown or subject to change? Can this receptacle be used for purposes other than welding equipment?

Thanks for responses!

 

[S'mise]

What criteria are used when sizing a generic 3 phase, 480V welding receptacle in an industrial plant? ... What dictates sizing of conductors and OCP of a welding receptacle if the specifics are unknown or subject to change? Can this receptacle be used for purposes other than welding equipment?....

Size the conductors for the maximum amperage that can be used. If you have a 60 amp receptacle base everything on that. (you can always put smaller fuses in later)

Yes, Recept can be used for other things.

 

[cadpoint]

One can't run a size of wire with the particulars unknown and not-set.

It funny that we are required to size a circuit or service according to it's needs, what the needs might be all still needs to be addressed!

The safe thing to do is to label the power point as to the power available and even where its orginates!

OK, I can't grasp exactly how the plug is to be used?!

JMO

 

[ZinskI/E]

The question has arisen from a need for temporary power for a turnaround. The owner wants to connect to a welding receptacle to feed a 480/120V transformer to feed a tool/equipment trailer (amperage requirements appear to be within reason based on breaker size).

In a plant I realize the AHJ is usually in-house, so we will abide by their decision. However, I am still curious about the engineering guidelines used in selecting generic welding receptacles considering duty ratings for machines are so variable.

I guess what I'm trying to get at is regardless of this specific need, if I were to sit down and specify a welding receptacle's conductors and OCP without knowing the exact equipment, what would I do?

 

[iceworm]

What criteria are used when sizing a generic 3 phase, 480V welding receptacle in an industrial plant? xxx

The question has arisen from a need for temporary power for a turnaround. The owner wants to connect to a welding receptacle to feed a 480/120V transformer to feed a tool/equipment trailer (amperage requirements appear to be within reason based on breaker size). xxx

xxx I guess what I'm trying to get at is regardless of this specific need, if I were to sit down and specify a welding receptacle's conductors and OCP without knowing the exact equipment, what would I do?

After the plant is built, "Welding Receptacles" in industrial plants are used 1000:1 for temporary power over actually powering a welding machine. Your example of the equipment trailer temporary power is a normal use.

So, how to specify a "welding receptacle" feeder - when you don't know what you are going to feed?

First, regardless of the name - "Welding Receptacle" - these are general purpose receptacles. Art 630 is not much of a concern.

I would start with doing some homework. You have to get familiar with the clients needs. Since they can't tell you, you have to figure it out - that's part of the engineering. And, yes, you are doing engineering.

1. Go look at existing WR feeders - wire size and OCP. Get the nameplate data from the existing receptacles. Hopefully there will be some uniformity.

2. Go to the maintenance department and see what they have for welding machines. Get the nameplate data. Go to the plant construction manager. Ask what the contractors bring in for welding machines. You may have to call your favorite contactor and ask what they have.

3. Also ask (both maintenance and construction) what other equipment is regularly plugged into these receptacles. Get the nameplate data.

How far you go is up to you - just remember, you are the engineer of record.

Compare the existing spec with the intended use. They should match - after all, the receptacles are being used. If so, make your new one match (as long as it meets code for wire size, OCP, receptacle).

If the existing spec doesn't match - the intended use is more power than the existing receptacles can supply - the people you are asking aren't telling the truth. They are likely telling you what they would like to see. I don't have any suggestions to fix this.

After all this is done and you feel comfortable with the clients needs (as opposed to wants), my experience is that 99.99% of all the WRs I have seen, or specified and installed, have been 60A OCP, 60A conductors, 60A 4W receptacles - no neutral, no 277V loads. Any equipment requiring more power gets a temporary (art 590) direct connection to an MCC bucket.

Good luck. Let us know how it coes out

So sayeth the worm

ice

 

[renosteinke]

Let's be clear on one thing: there is no such thing as a 'generic' welding receptacle. Period.

Welders (or is it 'weldors?) use massive amounts of current, occasionally, for moderate amounts of time. Thus, the rules.

There's no getting out of looking at the actual machine they will use. You cannot control what machine they might use next year. Let the nameplate be your guide. Insist that YOU see it, or have a picture of the ENTIRE nameplate - don't settle for them handing you a note with amps and volts on it. That other info actually means something.

Just saying 'well, it's a 60-amp plug, so I'll run a 60-amp circuit' is simply wrong. Doing so will only create a hazard AND piss off the customer.

The key factor is the 'duty cycle' of the welder. I've seen situations where the NEC would allow a 100-amp breaker on #12 wire!

Indeed, let's look at that little POS welder I just mentioned. Had I run the #12, there's a real good chance that the next machine would have been too big for the wire. Meltdown time.

Yet, had I used a 60-amp breaker, there's a real good chance that there would be nuisance tripping.

You wouldn't want to run '100-amp' wire, simply because it need much bigger pipe and won't fit in the lugs of the receptacle.

My advice is to run the biggest wire that the device will take, and size the breaker as the nameplate recommends. This will almost always result in there being 'enough wire,' and allow for a larger breaker than you would usually use for a 60-amp device.

I also advise using pipe- if for no other reason that you can pull larger wires later. Should they have a meltdown, the pipe (as a ground path) will help the breaker trip faster.

 

[iceworm]

Let's be clear on one thing: there is no such thing as a 'generic' welding receptacle. Period. xxx

Hummm - sounds like you are kind of waffling and not real positive about this.

I agree that a dedicated welding machine receptacle in a welding shop, specified to power a specific welder is not generic.

However, my translation is the OP is speaking of the "welding receptacles", commonly scattered through industrial plants. Although they are called "welding receptacles" they are rarely used as welding receptacles. And, yes, these are pretty generic as in general purpose.

ice

 

[ZinskI/E]

Thanks to all for the input thus far!

It seems iceworm and Renosteinke have nailed the issue on the head. Reno - your reservations are the same as mine: without knowing the duty cycle, ampacity, or any other nameplate information on the "intended" welder, how would one know how the circuit was designed?

Iceworm - your advice seems sound and is much appreciated. I will be on site next week and will have the opportunity to inspect actual field conditions rather than the imperfect scanned documentation of the installation. Hopefully the conductors are sized to suit the OCP, then the question has an easier answer. My experience in this particular plant is that conductors are well-sized to compensate for voltage drop at FLA, so (fingers crossed) chances are that even if the installation was designed according to 630, the conductors may be suitably sized to the OCP. As it is a temporary connection, I wouldn't be opposed to voltage drop over 5% as long as it poses no threat of damage to connected equipment.

As you have stated that in your experience the vast majority use of these welding receptacles is for use other than an actual welder, it would make sense to design the circuits to regular branch circuit constraints rather than the "looser" exceptions permitted for a dedicated welding receptacle. I will most certainly consider that in any future designs. Oversized conductors could be terminated on a receptacle using reducing barrels to suit lug sizes. Hopefully the original designer had the same mindset!

 

[S'mise]

....Just saying 'well, it's a 60-amp plug, so I'll run a 60-amp circuit' is simply wrong. Doing so will only create a hazard AND piss off the customer..

Care to elaborate on this hazard? I understand the high starting current of welders require larger fuses but the circuit is still protected by a (properly sized) ocpd.

As far as pissing off the customer, They didn't specify the welder load.(not weldor)So they might blow some fuses. Oh well, but the place won't burn down. It could be a design problem it you install a 30a fused disconnect and then you find out you need 40a fuses to start a 30a welder.

 

[ZinskI/E]

Field Confirmation

Field Confirmation

Iceworm - the conditions in your experience are the same as I found: 60A OCP, #6 Cu TC, and a 4W 60A welding receptacle. Appears we shouldn't have any issues with our temporary power connection.

Thanks again for the replies.

 

[irfan2222]

LV vs welding receptacles

LV vs welding receptacles

Question: Can AC Distribution Panel be used instead of LV MCC (LV switchgear) to supply to welding receptacles? is there a safety hazard if AC Distribution panel is used?