welder question

[Turbo1002]

I was looking at this welder today and the id plate has me confused. I attached a photo. The plate basically says use a 20amp branch circuit. When I looked at the plug it has a 15amp configuration. The cord has not been replaced it is all factory. How is this allowed?

 

[iwire]

It looks like it has a 20% duty cycle, that would mean 14 AWG is more than enough.

If you install at least two 15 amp receptacles (one duplex) the code will allow you to use a 20 amp breaker to supply it.

 

[chris kennedy]

how is this allowed?

110.3(b)...

 

[Turbo1002]

110.3 b is pretty funny. Basically, if the manufacture says it is ok then it is? I understand you are allowed to install 20 amp breakers with 15 amp devices. How can the manufacture use a receptacle which is designed for a max 15 amps and draw 20amps?

 

[LarryFine]

How can the manufacture use a receptacle which is designed for a max 15 amps and draw 20amps?

The potential exists for almost everything that comes with a 15a plug.

 

[don_resqcapt19]

It really doesn't matter. If you compare the "guts" of a 15 amp receptacle and a 20 amp receptacle of the same brand and series, you will find that they are identical. The only difference will be that the face plate on the 20 amp one will have the "T" slot.

 

[chris kennedy]

110.3 b is pretty funny.

One of my all time favorites along with 90.4.

 

[Turbo1002]

Thank you all for your responses. Although, I still don't see why this is allowed to be done. If manufactures can install 15amp plugs and draw 20 amps through them why have a 20 amp plug design?

 

[iwire]

Thank you all for your responses. Although, I still don't see why this is allowed to be done. If manufactures can install 15amp plugs and draw 20 amps through them why have a 20 amp plug design?

You need to look at Article 630 for welders.

For that 20 amp, 20% duty cycle welder you would only be required to provide a conductor rated 9 amps.

Now obviously we would not drop to less than a 14 AWG but ...


Lets say your welder was 100 amps with a 20% duty cycle

Table 630.11(A) tells us we could multiple the 100 amps by .45

100 x .45= 45 amps, so we could run 8 AWG THHN and use a 100 amp breaker to supply it.

Why?

Because of the welders duty cycle, a welder with a 20% duty cycle can only weld for 20% of each hour which means the conductors will not be overheated.

 

[Turbo1002]

I see. So welders have exceptions to plug designs and amperage ratings because of the duty cycle. Even though it draws more than 15 amps it is ok to be in a 15 amp receptacle because it should only be welding 2 out of every 10 minutes. Is this correct? Thank you.

 

[glene77is]

Because of the welders duty cycle,
a welder with a 20% duty cycle can only weld for 20% of each hour which means the conductors will not be overheated.

iWire,
Should that read "can only weld for 20% of each cycle" ?

 

[Turbo1002]

A welders duty cycle is based on 10 minutes. So if it is 20% duty cycle then a 2 minute weld on max setting is the longest weld you can make. Then the machine must rest for 8 minutes. You can weld longer if the amperage setting is turned down for thiner metals.

 

[iwire]

A welders duty cycle is based on 10 minutes.

Thanks! I did not know that and was wondering about it.

So if it is 20% duty cycle then a 2 minute weld on max setting is the longest weld you can make. Then the machine must rest for 8 minutes. You can weld longer if the amperage setting is turned down for thiner metals.

That is my understanding as well.