15A outlets on 20A circuits and tandems

[Prashun Patel]

Can I put a 15A outlet on a 20A circuit? I used to think 'yes'. But a respected friend is counselling otherwise.

Second, why do some townships (mine) prohibit the use of tandem breakers (2 breakers in a single slot). I had to remove the tandems in my box that a contractor installed a few years ago - even though I had about 1/3 of the slots emtpy in the box....

[Chris Lindell]

Sure, as long as the wire is rated for 20 amps along with the circuit breaker, if the 15amp outlet shorts, the breaker should still kick out.

[Larry Marley]

code may require receptacle to have same rating as breaker.
I recommend asking the same township that did not like your tandem breakers.

[Chris Lindell]

Very good point, didn't think about that - if they don't like the tandems they may have a stricter stance on the outlet as well

[David G Baker]

I use #12 wire, 20amp breakers and 20amp receptacles on almost all of my circuits except for equipment and appliance circuits that require larger breakers, etc. I also run a lot of wire so I don't put too many receptacles on any one circuit.
Can't imagine a local code not allowing tandems unless it is in a kitchen, laundry room or areas where code requires single appliances on one circuit.
I got caught in California having something else on the same circuit as my washing machine and had to run another wire for the other item.

[Rob Russell]

Per NEC section 210.21(B)(3) and Table 210.21.(B)(3), you may use 15A receptacles on a 20A circuit provided it's not a single 15A receptacle.

What does that mean?

Our standard receptacles are a duplex receptacle. That means you could have a 20A circuit supplying (1) 15A duplex receptacle and it would meet the NEC.

In terms of the half-size breakers, it's possible to overload a panelboard if you use too many of those half-size breakers. There is a limit on the number of circuits that can be in a panelboard and a 240v circuit counts as 2. I think that limit is either 42 or 44, but couldn't find it in the code.

[Dan Friedrichs]

Unless I'm misunderstanding something, I think the answer to your question is "No!!!!!".

If you have a 20A breaker, you need an outlet rated for 20A, as well. The current rating on an outlet is based on the thickness of the conductors inside of it, and if you exceed that, you risk them getting hot/melting/etc.

Ultimately, the rating of everything needs to match or exceed that of the breaker. If you have a 20A breaker, you need wire that can handle at least 20A, and an outlet that can handle at least 20A. The wire and outlet could be rated for much more current, but not less!

EDIT: Rob is right. I was thinking a single receptacle, but if you use duplex, it's acceptable because presumably you won't pull all 20A out of just one of the two receptacles.

But for the very minor cost difference, why bother with 15A?

[David G Baker]

I use the 20 amp receptacles because they are much easier to wire when using #12 wire. I also pay a little more and get the back insert/screw tork receptacles, they make the job go much faster and easier to fit the wires into the box.

[Prashun Patel]

I'm just trying to reuse/recycle outlets I already have.

[Rick Christopherson]

There is a limit on the number of circuits that can be in a panelboard and a 240v circuit counts as 2. I think that limit is either 42 or 44, but couldn't find it in the code.

That's because it is no longer listed as a code requirement. It used to be 42, but there is no limit.

As for the half height breaker issue, it probably is not a local code requirement per se, but because the load center is not rated for them. The code would require that you comply with the ratings of the equipment.

[Rob Russell]

Rick - was it the '05 or '08 versions of the NEC that dropped the 42 circuit limit?

[Bill Brady]

Yes you can use a 15A receptacle on a 20A circuit. The devices you plug in will be 15 A devices which are the normal for most. You may have had to remove the tandem breakers, not because of the breakers but because the wires were not installed properly, meaning a multi wire circuit was not split between both sides of the box. A multi wire circuit is 2 hot wires sharing a neutral, if the hot wires are not on seperate phases in the box it will overload the neutral they share.

[Rollie Meyers]

That's because it is no longer listed as a code requirement. It used to be 42, but there is no limit.

As for the half height breaker issue, it probably is not a local code requirement per se, but because the load center is not rated for them. The code would require that you comply with the ratings of the equipment.

That ONLY applies where the 2008 NEC has been adopted otherwise the 42 circuit rule still applies. Your are still limited to what a manufacturer has labeled the panel to accept.(which is what you said in the last sentence of the last paragraph ).

[Rob Russell]

Bill,

Using "tandem" breakers (what I called the "halfsize" breakers) has nothing to do with multi-wire circuits in the context of this discussion.

It is absolutely allowed (unless the local jurisdiction prohibits it) to use a pair of half-size breakers to feed (2) separate circuits.

Rob

[AL Ursich]

If you look at a 15 amp and a 20 amp receptacle you will see thinner materials on the 15 amp that if under load could get hot and melt due to the thinner material rated at 15 amps but drawing close to 20 amps before tripping.

This is the worst case senerio.... Every winter you read about Home Fires using a electric heater in a bedroom. Imagine this bedroom having a 20 amp breaker, 12 gage wire and a 15 amp receptacle and a electric heater. Most heaters draw about 15 amps on high. See where the Fire Investigator will find the 15 amp receptacle melted and the source of the fire.... Now your homeowners insurance tells you that you had a sub- standard homeowner installed outlet causing the fire and will not pay....

Worst case.... But real world...

AL