14-50 on 100 amp breaker? Ok to use?

[CyberGus]

@Jeremy3292 has given both thumbs-up and thumbs-down to @gearchruncher in this thread.

It’s like running a humidifier and a dehumidifier at the same time

I’m so confused

 

[Jeremy3292]

@Jeremy3292 has given both thumbs-up and thumbs-down to @gearchruncher in this thread.

It’s like running a humidifier and a dehumidifier at the same time

I’m so confused

Your insinuation being that because someone has a bad post they can’t also have a good post and vice versa? A person can only either be stupid or smart? I give credit where credit is due and I criticize where I think criticism is warranted. I would expect the same from others in regards to all of my posts as well.

Substance over form.

Additionally, this thread got derailed with useless nonsense earlier and away from the main topic (for which I played a role in), which was can you use a 100 amp breaker on a 14-50 receptacle, and the answer is simply no.

 

[stopcrazypp]

Funny enough, upon further study:


Basically, there needs to be the potential for the circuit to be overloaded for the oversizing of the circuit to occur. More fun, is that this is not allowed in Canada, where the receptacle HAS to match the circuit rating.


My understanding here is that at no time the load on the other end of the receptacle should be allowed to draw more than 50A, which is fundamentally a limit of the receptacle if designed correctly. I agree that it is not designed to "fail safely" which is a limitation of US code (compared to UK codes). Then again the reason we use protection is for the times when thing aren't working as expected, but in this case the failure point would remain at the receptacle, which can happen for for all sorts of reasons.

Actually as per my previous post, according to NEC 630.12, electric welders may draw up to 200% of the conductor rating for short periods (AKA 100A on a 50A circuit), so you can easily find welders that draw more than 50A that are used on 14-50 or 6-50 receptacles (and NEC allows you to install up to a 100A breaker in that case). Obviously this exception does not apply to EV charging (which is the worst type of load given it's continuous for hours).

The point is there is nothing in the receptacle itself that prevents you from doing that. It'll happily burn itself up if you run 200% of its rated current through it.

 

[3sr+buyer]

Regarding the 120V 20A circuit with 5-15 receptacles, why wouldn't you put 5-20 receptacles on it, since 5-20 receptacles accept both 5-15 and 5-20 plugs?

Photo below ( By Yak99 - I, user Yak99, created this work entirely by myself, and hereby release it into the public domain., Public Domain, File:NEMA 5 1 devices2.jpg - Wikimedia Commons ) shows 5-15, 5-20, and obsolete 1-15, 1-20 receptacles.

 

[gearchruncher]

Regarding the 120V 20A circuit with 5-15 receptacles, why wouldn't you put 5-20 receptacles on it, since 5-20 receptacles accept both 5-15 and 5-20 plugs?

Because there are basically no products in the USA that use a 5-20, and because they are so unusual, they are about 5X the price of a 5-15, so no contractor would choose them when building a house.

The only place I have run into them is in places actually meant for L1 EV charging. I have a 5-20 adapter for my UMC and it's a nice boost when you run into it.

 

[davewill]

Because there are basically no products in the USA that use a 5-20, and because they are so unusual, they are about 5X the price of a 5-15, so no contractor would choose them when building a house.

The only place I have run into them is in places actually meant for L1 EV charging. I have a 5-20 adapter for my UMC and it's a nice boost when you run into it.

Actually, 5-20s are pretty ubiquitous in a lot of commercial buildings, I've found.

 

[rpiotro]

The easiest way to think about it is that the breaker must match the smallest amperage of the wiring or receptacle, so that all parts of the circuit are protected.

A setup that may be moderately common and allowed is:

Receptacle: 50A
Wiring: 40A
Breaker: 40A

This is allowed, because the breaker matches the smaller amperage (of the wiring). It may be done because there are no NEMA 14-40 or 6-40 receptacles or plugs. A 32A EVSE may be plugged into such an outlet.

That is exactly what I have. 14-50 receptacle with 8 gauge wiring and a 40 amp breaker. I have placarded it to warn it is a 40 amp circuit. 32 amp max continuous load. It was installed by a long time acquaintance that is not only a certified electrician but also a certified electrical inspector. And he is very meticulous. He knows what he is doing.

There is no way he would do something that is dangerous or does not meet code.

 

[Jeremy3292]

That is exactly what I have. 14-50 receptacle with 8 gauge wiring and a 40 amp breaker. I have placarded it to warn it is a 40 amp circuit. 32 amp max continuous load.

Exactly what I recommended earlier. A simple label is a great choice just to be certain in the future.

 

[Jedi2155]

Regarding the 120V 20A circuit with 5-15 receptacles, why wouldn't you put 5-20 receptacles on it, since 5-20 receptacles accept both 5-15 and 5-20 plugs?

Photo below ( By Yak99 - I, user Yak99, created this work entirely by myself, and hereby release it into the public domain., Public Domain, File:NEMA 5 1 devices2.jpg - Wikimedia Commons ) shows 5-15, 5-20, and obsolete 1-15, 1-20 receptacles.

I think that's the first time I've seen a a 6-15R/6-20R receptacle on the right! I took me a while to figure out what that was.

Am I right?

 

[3sr+buyer]

I think that's the first time I've seen a a 6-15R/6-20R receptacle on the right! I took me a while to figure out what that was.

The ones on the right are obsolete 1-15 and 1-20 receptacles (non-grounding predecessors to 5-15 and 5-20 receptacles on the left).