20 amp wire on 15 amp breaker?

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Libby

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If I have a run of 20 amp wire on a 15 amp breaker can I connect the 20 amp wire to 15 amp outlets and switches?
 

allenwayne

Senior Member
I worked for a company that only used #12 wire till they realized the cost factor with using #14.The reason was, but they didn`t admit it at the time was they only had installers well almost only !!!! They used #12 so that it was a no brainer install,install and not have to think.

They also only installed #6/2 for electric heat/A/C, until the issue of a 10K heat strip made them think on that one.But when trim out time came depending on the manufacturers breaker we could use the #6 on a 30 amp or 25 breaker the ones that weren`t rated for that size wire it was a big blue wire nut and a downsized wire.But unless there is a data plate that says max.OCPD 15 amp why even bother.On a receptacle circuit as long as there is more than one single device using a 15 amp receptacle on a 20 amp circuit is good to go.
 

romeo

Senior Member
20 amp wire on 15 amp breaker

20 amp wire on 15 amp breaker

Libby said:
If I have a run of 20 amp wire on a 15 amp breaker can I connect the 20 amp wire to 15 amp outlets and switches?

I agree that it is code compliant. But other than to compensate for voltage drop,what is the advantage? Sounds to me like a home owner doing wiring thinking that he did a great job because he over sized the conductors,then violated the conductor fill. I always felt that wiring to code was normally a safe. However there are always exception to the rules in some cases.
 

Dennis Alwon

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romeo said:
I agree that it is code compliant. But other than to compensate for voltage drop,what is the advantage? Sounds to me like a home owner doing wiring thinking that he did a great job because he over sized the conductors,then violated the conductor fill. I always felt that wiring to code was normally a safe. However there are always exception to the rules in some cases.
Wiring to code is a minimum. Compensating for voltage drop is very wise in some situations. That is the only advantage one needs to have so don't knock it. I have done this and you can easily do it without overfilling the box. Calculate a 1000 watt heater at a distance of 100 feet from the panel and the formula will suggest a #10 wire to comply with the footnote of 3% voltage drop.
 

infinity

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bikeindy said:
you can use 15A devices even if you use a 20A breaker on a 20A wire, you can not use a 20 A device on a 15 A circuit.


You could use a single 20 amp receptacle on a 15 amp circuit. You cannot use a duplex or multiple receptacles.
 

romeo

Senior Member
20 amp wire on a 15 amp breaker

20 amp wire on a 15 amp breaker

Dennis Alwon said:
Wiring to code is a minimum. Compensating for voltage drop is very wise in some situations. That is the only advantage one needs to have so don't knock it. I have done this and you can easily do it without overfilling the box. Calculate a 1000 watt heater at a distance of 100 feet from the panel and the formula will suggest a #10 wire to comply with the footnote of 3% voltage drop.

Either I was not thorough about my explanation or you miss understood. I said other than to compensate for voltage drop ( that is a good idea ) what is the advantage to over sizing a conductor?
 

infinity

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romeo said:
Either I was not thorough about my explanation or you miss understood. I said other than to compensate for voltage drop ( that is a good idea ) what is the advantage to over sizing a conductor?


Another reason would be for future consideration. We often will run a 10/3 MC cable to dedicated copier receptacle even when the existing machine is 20 amps, and 120 volts. Many times a newer, larger copier will replace the older one and will require a larger circuit. Since the conductors are already oversized a simple change out the CB and receptacle would be easy.
 

Dennis Alwon

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infinity said:
Look at 210.21(B)(1).
Trevor I think Table 210.21(B)(3) clearly states that a 15 amp circuit cannot have a 20 amp receptacle. Article 210.21 (B)(1) IMO means you cannot have less than that of the branch circuit. It does not say you can have more-- "not less than" would imply you could have more, however Table 210.21(B)(3) nullifies that statement.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
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The reason you can't place a 20a receptacle on a 15a circuit is that the slot shape of a 20a receptacle implies that the circuit is capable of supplying equipment that comes equipped a 20a plug, meaning that a 15a circuit is not capable of supplying the power the equipment with the 20a plug requires.

Whew!


Cavie said:
20A circuit can have 15 amp recp. go figure.
Unless it's a single-receptacle circuit.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
LarryFine said:
The reason you can't place a 20a receptacle on a 15a circuit is that the slot shape of a 20a receptacle implies that the circuit is capable of supplying equipment that comes equipped a 20a plug, meaning that a 15a circuit is not capable of supplying the power the equipment with the 20a plug requires.

Whew!



Unless it's a single-receptacle circuit.

There is no problem if we have a 15 amp receptacle on a 20 amp breaker because nothing requiring 20 amps will plug into it.But we could put a 20 amp load on a 15 amp breaker if we permit that 20 amp receptacle.
 

don_resqcapt19

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Dennis,
Trevor I think Table 210.21(B)(3) clearly states that a 15 amp circuit cannot have a 20 amp receptacle. Article 210.21 (B)(1) IMO means you cannot have less than that of the branch circuit. It does not say you can have more-- "not less than" would imply you could have more, however Table 210.21(B)(3) nullifies that statement.
210.21(B)(3) has no effect on 210.21(B)(1) as (B)(3) only applies to a branch circuit supplying two or more receptacles or outlets, while (B)(1) applies to a single receptacle installed on an individual branch circuit. Please note that a duplex receptacle is two receptacles.
Don
 

Dennis Alwon

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don_resqcapt19 said:
Dennis,

210.21(B)(3) has no effect on 210.21(B)(1) as (B)(3) only applies to a branch circuit supplying two or more receptacles or outlets, while (B)(1) applies to a single receptacle installed on an individual branch circuit. Please note that a duplex receptacle is two receptacles.
Don
Again I stand corrected...
 

infinity

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don_resqcapt19 said:
Dennis,

210.21(B)(3) has no effect on 210.21(B)(1) as (B)(3) only applies to a branch circuit supplying two or more receptacles or outlets, while (B)(1) applies to a single receptacle installed on an individual branch circuit. Please note that a duplex receptacle is two receptacles.
Don


That was my point, table 210.21(B)(3) is not for a single receptacle. A single receptacle is permitted to be rated larger than the circuit ampacity. So a 20 amp single receptacle is permitted on a 15 amp circuit.
 
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