80% limit

[SNations]

I have another electrical question for everybody.

NEC section 210.23(A)(1) says that for 15 and 20 amp circuits "The rating of any one cord-and-plug connected utilization equipment not fastened in place shall not exceed 80 percent of the branch-circuit ampere rating."

So am I correct that this is a requirement not for the guy running wire through your house, but it's a requirement for the folks making your hair dryer.  A manufacturer can't (or shouldn't) make anything with a standard plug for use on a 15-amp circuit such that the appliance is designed to use more than 12 amps.  If it's got a plug so that it can only be plugged into a 20 amp receptacle then it can't be designed to use more than 16 amps.  An electric clothes dryer on a 30-amp circuit shouldn't be designed to use more than 24 amps.  

Thanks

Steve

[Jim Katen]

Remember that 210.23 only applies to "multiple-outlet branch circuits." When a branch circuit has two or more outlets, then any one piece of equipment can't exceed 80% of the branch circuit amp rating. Designers and installers need to keep this in mind when designing and installing the electrical system. This part of the code applies to them. 

A manufacturer can still make a piece of equipment with a standard 15-amp plug that uses more than 12 amps but it should only be used on an "individual branch circuit" and, of course must not exceed 15 amps (per 210.22) Same goes for a dryer on a 30 amp circuit. That's why some appliances include instructions to power them only from dedicated (individual) circuits. 

[SNations]

3 hours ago, Jim Katen said:

Remember that 210.23 only applies to "multiple-outlet branch circuits." When a branch circuit has two or more outlets, then any one piece of equipment can't exceed 80% of the branch circuit amp rating. Designers and installers need to keep this in mind when designing and installing the electrical system. This part of the code applies to them. 

A manufacturer can still make a piece of equipment with a standard 15-amp plug that uses more than 12 amps but it should only be used on an "individual branch circuit" and, of course must not exceed 15 amps (per 210.22) Same goes for a dryer on a 30 amp circuit. That's why some appliances include instructions to power them only from dedicated (individual) circuits. 

So if a manufacturer makes a piece of equipment that uses 14 amps (with a standard 15 amp plug) then how do they ensure that it's only used on an "individual branch circuit"?  Just with instructions?  That seems awfully tenuous to me. 

I can see how that might work for something like a clothes dryer or electric range.  But I don't see how that works for anything with a standard 15 amp plug, like a hair dryer or toaster oven.  The opportunities for the average person to violate the rule are just too great.

[Jim Katen]

I suspect that there's a complementary rule that's part of the UL listings for various products. That's why virtually all space heaters, toaster ovens, etc have limited power ratings.