15 amp wire in 20 amp cir

[wbalsam1]

I have been successful in every attempt at coaxing electricians to NOT intermix conductor sizes. Each time that I inspect a job where the installer has used 14/3 travellers on a 12/2 circuit and intended to protect at 20 amps, I have been successful in having this installer remove the 14/3 and replace with 12/3 or remove the 12/2 and replace with 14/2 and protect at 15 amps. I make every effort to disallow this and the company I work for also does not permit this, as a company policy. Nearly everyone in the industry around here considers this intermixing to be a poor wiring method. :smile:

 

[don_resqcapt19]

augie,

then you would be violating 402.11

I don't think so. If I install it per 402.10, it is not being used as branch circuit wiring.

402.10 Uses Permitted
Fixture wires shall be permitted (1) for installation in luminaires (lighting fixtures) and in similar equipment where enclosed or protected and not subject to bending or twisting in use, or (2) for connecting luminaires (lighting fixtures) to the branch-circuit conductors supplying the luminaires (fixtures).

Yes it is a very fine line and subject to debate. Like I said in my first post...just trying to muddy the waters a bit.
Don

 

[panelman]

Did I miss something?

Did I miss something?

It would seem logical that the conductor's rated load should match the breaker load. The whole point is to prevent overheating/overloading. Did I miss something ? Maybee there are some exceptions?

 

[peter d]

T310.16 says that the ampacity of #14 AWG is 20 amps. So while this would not be code compliant by 240.4, it would not be a hazard either.

 

[tallguy]

It would seem logical that the conductor's rated load should match the breaker load. The whole point is to prevent overheating/overloading. Did I miss something ? Maybee there are some exceptions?

Voltage drop

 

[benmin]

Lets muddy the water a bit...what if I use fixture wire from the switch to a single fixture?
Don

I'm not that familiar with fixture wire but I'm assuming it would need to be in conduit from the switch to the fixture. What kind of fixture wire would you use? You'ld probably get some eye rolling from fellow electricians

 

[don_resqcapt19]

I'm not that familiar with fixture wire but I'm assuming it would need to be in conduit from the switch to the fixture. What kind of fixture wire would you use? You'ld probably get some eye rolling from fellow electricians

Yes, it would have to be in conduit or flex. There are a number of conductors shown in Table 402.3. I am not saying that this would be a good idea, just trying to make the point that it may be permitted by the code rules.
Don

 

[Jim W in Tampa]

T310.16 says that the ampacity of #14 AWG is 20 amps. So while this would not be code compliant by 240.4, it would not be a hazard either.

It also tells you that breaker size is to be 15

 

[peter d]

It also tells you that breaker size is to be 15

That's what I said. Did you miss it?

I was pointing out that the wire will not be overloaded on a 20 amp breaker because #14 has a 20 amp ampacity. I don't know that I can say it much clearer than that. The 240.4 rules are some kind of "fudge factor" that the code writers put in.

 

[benmin]

just trying to make the point that it may be permitted by the code rules.

I agree. I'm surprised there hasn't been more opposition to this

 

[Jim W in Tampa]

That's what I said. Did you miss it?

I was pointing out that the wire will not be overloaded on a 20 amp breaker because #14 has a 20 amp ampacity. I don't know that I can say it much clearer than that. The 240.4 rules are some kind of "fudge factor" that the code writers put in.

Your missing something.14 wire can not have a 20 amp breaker.A #12 wire can be breakered at 15.Number 14 wire can not safely carry 20 amps.That rating clearly tells you to use 15 amp protection unless its used on a motor.Read where it sends you too.

 

[peter d]

Number 14 wire can not safely carry 20 amps.

Wrong....T310.16 tells me that it can.

 

[iwire]

Number 14 wire can not safely carry 20 amps

Jim that is absolutely untrue.

14 AWG can safely carry 20 amps.

The rules in 240.4(D) do not change the physical properties of copper wire.

I don't know why 240.4(D) exists, but it is not because 14 AWG can not safely carry 20 amps.

 

[Jim W in Tampa]

Jim that is absolutely untrue.

14 AWG can safely carry 20 amps.

The rules in 240.4(D) do not change the physical properties of copper wire.

I don't know why 240.4(D) exists, but it is not because 14 AWG can not safely carry 20 amps.

Call it what you want.Wire a house in number 14 and put it on 20 amp breaker and your getting red tag

 

[M. D.]

Jim #14 NMb is rated for 20 amps ,..if it were not ,.why would we derate from 20 amps when we have bundled them??

 

[Jim W in Tampa]

Jim #14 NMb is rated for 20 amps ,..if it were not ,.why would we derate from 20 amps when we have bundled them??

And 240.4d tells you what ? You simply can not fuse #14 lighting circuits with a 20 amp breaker.If it was safe they would let you.Your going to mess up some new green helper leting him think that way.Derating comes from the 90 degee colum.Love to see your kitchens on a rough.Inspector will laugh himself to death.

 

[iwire]

And 240.4d tells you what ?

Jim maybe you should go back and read it.

All it tell us is that for certain types of circuits we must use no more then a 15 amp breaker with 14 AWG, that IS NOT the rating of 14 AWG, the rating of conductors is found in 310.

What does 310.16 tell us?

You simply can not fuse #14 lighting circuits with a 20 amp breaker.

If you speaking of the branch circuit your right.

If it was safe they would let you.

But they do let us and it is safe.

There are many times when we can use 14 AWG at 20 amps.

Your going to mess up some new green helper letting him think that way.

No, we are going to straighten them out.

You are misleading them when you say 14 AWG is not rated 20 amps.

Love to see your kitchens on a rough.Inspector will laugh himself to death.

Who said anything about roughing a kitchen with 14 AWG, that would be a violation of 240.4(D) not an overload of 14 AWG.

 

[M. D.]

And 240.4d tells you what ? You simply can not fuse #14 lighting circuits with a 20 amp breaker.If it was safe they would let you.Your going to mess up some new green helper leting him think that way.Derating comes from the 90 degee colum.Love to see your kitchens on a rough.Inspector will laugh himself to death.

Jim I never said that you could fuse a # 14 serving a general lighting load with a 20 amp breaker , I said #14 nmb has an ampacity of 20 amps . They are two different issues.

 

[nankipoot]

I just want to say for the record again, I do allow mixed wire if fused to the smallest wire size in the cir. However I do all I can to try to stop this practice. The thing I tell them is, if you wire a bed rm with 20 amp wire and a 15 amp switch leg, then I will force you to fuse it at 15, then why waste the 20 amp wire and just do the whole cir in 15.

I also tell them that when I did new jobs (back in the day )one of the things I kept in mind was how to prevent call backs and how to do a "better than the other guy" job. One way was not to use any 15 amp wire...... I would explain the difference to the customer. I have seen outlets that were removed 2 or three times and the 15 amp wire would break at the back of the plug from the movement.

Oh this forum rocks! by the way

 

[petersonra]

I don't think this is an issue of safety, but rather what the code says. With a very few exceptions, you cannot use #14 wire on a BC protected by a 20A OCPD.