Section 210.21(B)(2) and (3)

[bphgravity]

I believe section 210.21(B)(2) along with its Table should be completely deleted from the code. We as installers have no control over how the user will plug in equipment to multioutlet branch circuits. To limit the load to a specific receptacle is not possible.

Also, I don't think 15-ampere receptacles should be on 20-ampere branch circuits. The purpose of a 20-ampere branch circuit is to permit 20-ampere loads be served. A 20-ampere cord and plug connected appliance cannot be used with a 15-ampere receptacle. Besides, Table 210.21(B)(3)does not permit 20-ampere receptacles on 15-ampere branch circuits for an identical reason. We don't allow people plugging in 20-ampere equipment to circuits only rated for 15-ampere, yet we allow 15-ampere receptacles be on 20-ampere circuits.

[ October 21, 2004, 12:24 PM: Message edited by: bphgravity ]

 

[petersonra]

Re: Section 210.21(B)(2) and (3)

I don't have a problem with 15A outlets on 20A circuits. The branch circuit protection is not there to protect the outlets or whatever equipment might be plugged in there, its there to protect the branch circuit wiring.

It also seems to make sense to continue allowing this as it allows more outlets to be served by the same branch circuit, thus potentially lowering costs.

 

[bphgravity]

Re: Section 210.21(B)(2) and (3)

Originally posted by petersonra:
I don't have a problem with 15A outlets on 20A circuits. The branch circuit protection is not there to protect the outlets or whatever equipment might be plugged in there, its there to protect the branch circuit wiring.

The concern isn't overcurrent protection. Its about allowing a 20-ampere circuit be used as a 20-ampere circuit. A 20-ampere circuit with 15-ampere rated devices limits the circuit as if it were only a 15-ampere circuit by limiting the total load on any one receptacle to 12-ampere plus you cannot plug in a 20-ampere appliance though it may be permitted to be served on that circuit. This is the case for all required 20-ampere circuits required by 210.11. All these circuits are supposed ot be 20-ampere circuits yet known of them are really capable of 20-ampere loads if 15-ampere devices are used.

 

[don_resqcapt19]

Re: Section 210.21(B)(2) and (3)

Bryan,
I also see no problem with 15 amp duplex receptacles on a 20 amp circuit. You can use more than one portable appliance on a single circuit. Also I think that 20 amp receptacles are ugly and that most housewifes would not want to see them in their kitchens. This proposal is not a safety issue and there for is not within the scope of the code.

A 20-ampere circuit with 15-ampere rated devices limits the circuit as if it were only a 15-ampere circuit by limiting the total load on any one receptacle to 12-ampere plus you cannot plug in a 20-ampere appliance though it may be permitted to be served on that circuit.

A single 15 amp receptacle is not permitted on a a 20 amp circuit, but a duplex is and you can plug a 12 amp load into each of the receptacles on the 15 amp duplex.
Don

 

[bphgravity]

Re: Section 210.21(B)(2) and (3)

Originally posted by don_resqcapt19:
...but a duplex is and you can plug a 12 amp load into each of the receptacles on the 15 amp duplex.
Don

What about a 16-amp load? What about an appliance with a 20-ampere attachment plug? A homeowner will still use the receptacle and exceed the 12-ampere requirement, and will purchase an adaptor to make the plug fit. Those are possible safety hazards, in my mind anyway.

 

[don_resqcapt19]

Re: Section 210.21(B)(2) and (3)

Bryan,

What about an appliance with a 20-ampere attachment plug?

I've never seen a household appliance other than an air conditioner with a 20 amp cord cap. Are there others?
Don

 

[derwith]

Re: Section 210.21(B)(2) and (3)

Is it true that all other plug and cord connected equipment is amphere rated and voltage rated and are not interchangeable? And is it true that whether it is straight blade or twist-lock you can't connect to a wrong device.

 

[renosteinke]

Re: Section 210.21(B)(2) and (3)

From personal experience, I know for a fact that UL tests 15-amp receptacles to the same standards as 20-amp receptacles. This removes any concern as to safety.
UL standards also require appliances to have the proper plug; something with a 15 amp plug will not ordinarily draw more than the allowed current, and fault conditions have been judged to be likely to also exceed 20 amps.

In practical terms, there are many combinations of normal appliances that, together, are likely to exceed 15 amps total. That's why we get to use 20 amp circuits- as long as we have more than one receptacle on the circuit.

In short, this is an old issue, was discussed ad infinitum, and this is the compromise that everyone agreed upon. It is also why most places have limits on how many receptacles can be on a circuit.

 

[bphgravity]

Re: Section 210.21(B)(2) and (3)

If 15A and 20A receptacles are essentially the same, and if there is no safety issue using either/or, then why can't a 20A receptacle be on a 15A branch circuit?

 

[charlie]

Re: Section 210.21(B)(2) and (3)

Then, if you really did have a 20 ampere plug, you could overload the circuit with the single appliance even if nothing else was plugged into the circuit.

 

[hurk27]

Re: Section 210.21(B)(2) and (3)

There is a reverse way to look at this.
And it is found in 210.23(A)(2)

If it was required to only allow that when multible receptacle are on one circuit, any one appliance should only use 50% of the circuit rating then if we have 20 amp receptacles installed and a home owner buys a commercial microwave that has a 20 amp plug on it what happen when this home owner tries to use a toaster or a coffee pot. If 15 amp receptacles are installed it might force a home owner to hire an electrician (we hope) to change the plug who should show the home owner that a dedicated circuit should be installed for this microwave.
Yes this wont happen in every case but it will happen in the cases where the home owner does want to do it the right way.

Most instructions that are suppled with a appliance that has a 20 amp cord on it will require that a dedicated 20 amp circuit must be used or the warranty is voided.

[ October 28, 2004, 01:45 AM: Message edited by: hurk27 ]