Code violation Article 30amp recpt on 20 amp circuit

[steve66]

I can't see that as a code violation. Breaker might trip, but that's its purpose .

I have seen many other people post similar comments, and I completely disagree with this.

A 20A breaker does not trip at 21A. And breakers are not infallible, they can fail to trip when they should..

Load calculations are required by the NEC for all branch circuits, feeders, and services. You can't just add loads until the breaker trips.

IMO, this concept extends to receptacles and their branch circuits. You have to do the load calculations, and provide a branch circuit that can supply that load per 210.11, and 210.19A1.

Isn't that that pretty much the same violation that can happen anytime someone plugs into a multi-receptacle outlet circuit?

Yes, but 15 and 20 amp multi-receptacles circuits have special rules, like using #12 wire for a 20 amp circuit (even though #12 is rated for 25 amps.) And there is simply no way to know what might be plugged into a circuit like this. With a 30 amp receptacles, there is a good chance the device plugged in will need something in the 20-30 amp range.

I would like you to consider the following.

You are hired to wire a portable industrial machine, it must be cord and plug connected.

The machine has a minimum circuit size of 65 amps and a maximum overcurrent protection listing of 70 amps.

What size receptacle and cord cap are you going to use?

I believe I understand your point, but I don't agree the same logic would allow a 30A receptacle on a smaller branch circuit that corresponds with a smaller standard receptacle rating.

I know I'm in the minority on this one, but I'm still convinced this is a code violation.

 

[iwire]

A 20A breaker does not trip at 21A. And breakers are not infallible, they can fail to trip when they should..

I agree breakers have trip curves but if we cannot count on them to operate we have to shut the power plants down.

Load calculations are required by the NEC for all branch circuits, feeders, and services.

I agree.

You can't just add loads until the breaker trips.

Who is 'You' is that a trained person or a homeowner plugging the second 1,500 watt heater in the same 15 amp receptacle circuit.

IMO, this concept extends to receptacles and their branch circuits. You have to do the load calculations, and provide a branch circuit that can supply that load per 210.11, and 210.19A1.

As far as receptacle circuits those sections are ridiculous and entirely unenforceable when the NEC also allows more than one receptacle per circuit and multi-outlet adapters are readily available.

Yes, but 15 and 20 amp multi-receptacles circuits have special rules, like using #12 wire for a 20 amp circuit (even though #12 is rated for 25 amps.) And there is simply no way to know what might be plugged into a circuit like this. With a 30 amp receptacles, there is a good chance the device plugged in will need something in the 20-30 amp range.

Do over current devices work or not?

I believe I understand your point, but I don't agree the same logic would allow a 30A receptacle on a smaller branch circuit that corresponds with a smaller standard receptacle rating.

I know I'm in the minority on this one, but I'm still convinced this is a code violation.

Please take a stab at my question regarding the portable industrial equipment.

 

[steve66]

I would like you to consider the following.

You are hired to wire a portable industrial machine, it must be cord and plug connected.

The machine has a minimum circuit size of 65 amps and a maximum overcurrent protection listing of 70 amps.

What size receptacle and cord cap are you going to use?

AFAIK, receptacles jump from 60 A to 100A. So we need a 100 amp receptacle and cord cap for this application.

I believe your point is that in this example, we have to use a OCP device with a rating less than the receptacle.

 

[electricalist]

If a 20 amp breaker protecting #10 wire and a 30 amp device is causing this much distress,, i hope no one ever points out sec from the poco xfmr to the wide spot ( kwired) where usage is measure and alllllllllllllllll the way to the 1 st means of disconnect are only protected by the theory of an electrician and ok' d by an inspector...and the ocpd up stream.