20 amp circuit, #14 Switch Leg

[kwired]

Since the switch is only rated for 15A, then why not allow the switch leg to be #14AWG.

Maybe the NEC should require receptacles to be 20A and lighting circuits to be 15A, and you can't mix them.

But wait, that is design and not related to safety, and we all know the NEC should not be used as a design guide.:rotflmao:

But the switch is located inside a box where additional heating effects should they happen are hopefully contained within the box. The conductors may be part of a cable such as NM cable that has virtually no separation between the conductor and other objects and run near or in contact with combustible materials, like wood framing members, cellulose insulation, etc.

 

[mek421]

Let's say a 15 amp receptacle was installed on a 14 gauge leg off of a 20 amp breaker. Now let's say some highly intelligent person, probably through inappropriate use of relocatable power taps, overloads this receptacle, but only a little, let's say they have a 19 amp load that is continuous for some period of time even if not normally considered continuous.

Isn't this a fire hazard, since it is an overload that will not trip a breaker? Both along the 14 gauge wire and the receptacle? If it was 12 gauge wire to the receptacle, wouldn't the fire hazard only be at the receptacle?

 

[hurk27]

Dennis Spelled it out very clearly in post 17

With taps and motor loads that have built in protection from overloads we are protecting the conductor from overloads by the down streem overload protection or controlled loading, the conductor will still be protected from short circuit faults by the upstream protection device, but a receptacle or light fixtures one can not depend upon the user of the receptacle from installing more loads that could exceed the rating of the conductor but not trip the over current device, the NEC can't differentiate these variables as it would end up with a much bigger book.

Yes a single switch feeding a single medium base lamp socket would not be a fire hazard if the switch was on a 20 amp circuit as the #14 wire would be protected from overloads by virtue of the limited ability of loading, but in many cases fixtures could be added by someone in the future that could overload the #14 just as receptacles could be overloaded because there is no control to what someone can plug in to them, small space heaters is a good example of this.

One could say this could happen in a motor circuit, but I would say it would be more less likely.

Manufactures can design appliances with smaller conductors because they follow the same rules, they know how much each load takes in their appliance, and also know if a fault was to happen the breaker will still open, this is why we see smaller conductors in appliances.

 

[kwired]

Let's say a 15 amp receptacle was installed on a 14 gauge leg off of a 20 amp breaker. Now let's say some highly intelligent person, probably through inappropriate use of relocatable power taps, overloads this receptacle, but only a little, let's say they have a 19 amp load that is continuous for some period of time even if not normally considered continuous.

Isn't this a fire hazard, since it is an overload that will not trip a breaker? Both along the 14 gauge wire and the receptacle? If it was 12 gauge wire to the receptacle, wouldn't the fire hazard only be at the receptacle?

Possibly. I can tell you that there is a difference between specification grade or better 15 amp receptacles and the ones that only cost $.50 - $.75. The cheap ones have often melted down with only a 8-10 amp load connected to them at times.

I also don't think the 15 amp rating has as much to do with how much current the receptacle itself is capable of carrying as it has to do with the fact that a 20 amp receptacle simply has different pin arrangement. The application is more important than the ability of the receptacle to carry the load, as cord cap blades and receptacle contacts may be identical as far as how much metal they are made of in both 15 and 20 amp versions. Even 30 and 50 amp receptacles and cord caps are often identical other than the arrangement/design of pins that will prevent them from interchanging with one another. There are replacement cord caps that are for both 30 and 50 amp circuits, one pin is usually the only difference between many flat blade configurations in 30 and 50 amps, the replacement cap comes with both of those pins and you select which one you need based on whether you are using it as a 30 or 50 amp device, everything else is the same.

 

[kingpb]

You do realize they make 20 amp switches don't you? In many non dwelling installations a lighting circuit can be heavily loaded and we very seldom use any 15 amp switches

Roger

Yes, of course they make 20A rated switches. But most commonly used switches are 15A rated, and I'll bet the contractors bidding on large housing developments are not using 20A switches. Sure a custom home might, but then, the lights and plugs probably wouldn't be mixed either, and all sorts of extras would be planned.

For the typical, cut throat, cheapo, job, the switches will be 15A, and no reason not to use a #14 AWG switch leg. Heck, the #14AWG is capable of more than 15A anyway.

 

[kwired]

Yes, of course they make 20A rated switches. But most commonly used switches are 15A rated, and I'll bet the contractors bidding on large housing developments are not using 20A switches. Sure a custom home might, but then, the lights and plugs probably wouldn't be mixed either, and all sorts of extras would be planned.

For the typical, cut throat, cheapo, job, the switches will be 15A, and no reason not to use a #14 AWG switch leg. Heck, the #14AWG is capable of more than 15A anyway.

Any conductor is capable of more than in the Art 310 ampacity tables, but they will operate at elevated temperature levels:happyyes:

 

[roger]

Let's say a 15 amp receptacle was installed on a 14 gauge leg off of a 20 amp breaker.

We are drifting away from the OP, receptacles are specifically forbidden to be on a reduced tap, the following graphic would be 210.19(4)(c) in the 2011

Roger

 

[roger]

For the typical, cut throat, cheapo, job, the switches will be 15A, and no reason not to use a #14 AWG switch leg. Heck, the #14AWG is capable of more than 15A anyway.

I agree, and even in the typical cheapo residential job, it would be doubtfull that any switchleg would be ever be loaded to 1800 watts

Roger

 

[Volta]

I agree, and even in the typical cheapo residential job, it would be doubtfull that any switchleg would be ever be loaded to 1800 watts

Roger

Well except for the super-cheapo job, where the switchleg controls a receptacle only, as that costs less than a ceiling outlet. And the HVAC contractor didn't make get paid much money either, so the occupant is cold, but has a nice 1500 watt heater, and a fishtank, and a ...

 

[kwired]

Well except for the super-cheapo job, where the switchleg controls a receptacle only, as that costs less than a ceiling outlet. And the HVAC contractor didn't make get paid much money either, so the occupant is cold, but has a nice 1500 watt heater, and a fishtank, and a ...

You didn't finish the sentence ... and a 1500 watt heater in the adjacent room, also because the HVAC did not get paid, and it is on the same branch circuit:happyyes:

 

[Volta]

You didn't finish the sentence ... and a 1500 watt heater in the adjacent room, also because the HVAC did not get paid, and it is on the same branch circuit:happyyes:

I see you had to fix that house too!

 

[roger]

Well except for the super-cheapo job, where the switchleg controls a receptacle only, .

See post number 27

Roger

 

[Volta]

See post number 27

Roger

Ok, what'ch'a mean? My comment is about loading through a switchleg, of course the outlet in that illustration should be protected at 15 amps.

See post number 9.

 

[kwired]

I see you had to fix that house too!

Well, ya probably more than one of them over the years.

 

[roger]

Ok, what'ch'a mean?

My point is that specific code wording prohibits a receptacle from using conductor tap below the conductors ampacity, so even in the cheapest installations the OP's topic wouldn't come into play for a switched receptacle.


Roger

 

[growler]

(Withing the last few months I have had out-of-town guys install using that method and both were experienced North Georgia electricians who advised it was "standard practice at home".)

That may very well be true. I have not seen it but ever so often you hear stories of some jurisdiction that will allow a #14 switch leg on a 20 amp circuit.

Heck, if they are going to use #14 for the switch leg then why not just use #14 on the whole circuit and a 15 amp breaker ( it's a lighting circuit, residential)?

Plus I don't think they get real inspections in some areas of north georgia.

 

[hurk27]

I have heard of a few who tried to use the allowances for fixture wires to allow this, but thhn or NM is not listed as a fixture wire in table 402.3 and is only meant to connect a fixture to its outlet box which in many cases is only allowed to be 6', a switch box is not an outlet box, the one scary thing I have seen in the past is people daisy chaining can lights using 6' fixture whips with only 18 awg conductors, which are only rated for 6 amps per 402.5, I had a service call on some fluorescent fixtures in a drop ceiling where the office people mentioned smelling something burning before the breaker tripped and wouldn't reset, I found 10, 4 lamp fluorescent lay-in fixtures daisy chained using 18 awg fixture whips on a 20 amp circuit, the insulation on the wire between the first fixture and the rest was completely burned off.