Why do >15A devices not have 20A circuit plugs on them?

don_resqcapt19

Moderator
Staff member
Location
Illinois
A newish tenant texts me to say she keeps blowing her circuit breaker. Now, this is an old unrenovated apartment with 15A only circuits. And she's got an 1875W blow dryer! That's over 15A no matter how you slice it, and as I understand code, you shouldn't have a device pulling a steady load over 80% of circuit rating, right? The 1875W rating seems expressly designed to keep just under 80% of 20A.

I've told her she needs to get a 1200w blow dryer. But my question is: how is this hazard even possible, isn't this the reason 20A receptacles and plugs exist, to keep this from happening? Why does the 1875W device not have a 20A plug that won't go in a 15A receptacle? Even if I had a 20A bath receptacle circuit, it would have made no difference, she was doing her hair in the bedroom!
Actually when you look at the label on the blow dryer, I think you will find it is rated at 1875 watts at 125 volts, which is exactly 15 amps. That is why the listing permits the 1875 watt blow dryer to have a 15 amp attachment plug. The wattage at that voltage is just a marketing issue.
 

dirtynails

Member
Location
NJ
Actually when you look at the label on the blow dryer, I think you will find it is rated at 1875 watts at 125 volts, which is exactly 15 amps. That is why the listing permits the 1875 watt blow dryer to have a 15 amp attachment plug. The wattage at that voltage is just a marketing issue.
That presumes that the user has it on a line with no other load at all. Really only true for the dedicated GFCI in the bathroom, and that is now 20A anyway. I think my next move, before telling her to get a new dryer, is to actually see what her unit is pulling. Something has changed here, I know that this apartment has been on these screw in breakers for 20 years without significant issues, and the tenants have used microwaves and AC's. Now she says her 900w MW is flipping this breaker!
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
That presumes that the user has it on a line with no other load at all. Really only true for the dedicated GFCI in the bathroom, and that is now 20A anyway. I think my next move, before telling her to get a new dryer, is to actually see what her unit is pulling. Something has changed here, I know that this apartment has been on these screw in breakers for 20 years without significant issues, and the tenants have used microwaves and AC's. Now she says her 900w MW is flipping this breaker!
It doesn't presume anything...it is just the reason that the 1875 watt blow dryer is permitted to have a 15 amp rated plug.
 

JFletcher

Senior Member
Location
Williamsburg, VA
That presumes that the user has it on a line with no other load at all. Really only true for the dedicated GFCI in the bathroom, and that is now 20A anyway. I think my next move, before telling her to get a new dryer, is to actually see what her unit is pulling. Something has changed here, I know that this apartment has been on these screw in breakers for 20 years without significant issues, and the tenants have used microwaves and AC's. Now she says her 900w MW is flipping this breaker!
if she is running a microwave and a hairdryer on the same 15 amp circuit, there's no telling what else might be wired to it... sounds overloaded to me.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Guys just added some devices in a longtime customers garage existing circuit. Customer calls and says the CB is tripping along with a GFCI device.

Sent one back and he found a loose #14 on the 30 amp breaker. They didn't notice the amp rating of the breaker when they turned it off to extend the circuit.:?

Customer suggested I had installed it. Yea, right. He now has 15 amp breakers and the help has two 30 amp breakers in his pocket.
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
Guys just added some devices in a longtime customers garage existing circuit. Customer calls and says the CB is tripping along with a GFCI device.

Sent one back and he found a loose #14 on the 30 amp breaker. They didn't notice the amp rating of the breaker when they turned it off to extend the circuit.:?

Customer suggested I had installed it. Yea, right. He now has 15 amp breakers and the help has two 30 amp breakers in his pocket.
How does replacing with a lower (proper) sized breaker solve the tripping?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
How is a hair dryer not a continuous load if it's running for at least 10 minutes. I thought "non-continuous load" was motor startup and the like momentary draws. So shouldn't drawing even 100% of rated load for ANY length of time be disallowed? Like I said, it sure looks like the 1875W units are designed to stay under 80% of 20A.
"Continuous" is defined as 3 hours or more. Granted, when my daughter lived at home, 3 hours fussing with her hair was not unexpected, but she generally didn't have the blow dryer running the ENTIRE time...

Here's a question, please try not be horrified. The breaker in question is a screw in replacement for glass fuses. (yes, a new riser and panel is due when the place is renovated, I haven't just replaced the panel because the new one will be in a different location). Could this breaker "break in" from being tripped too many times and start to trip at lower current levels? I have already replaced it with a new one, and am waiting for her report.
Possible, but unlikely, at least when talking about molded case circuit breakers. Those little things that screw into an Edison base though, it might be an issue. They say they are UL listed, but not under UL489 for circuit breakers. I don't know what they are listed for however, the UL File number that Cooper gives for theirs does not come up as valid in UL's search system. Probably listed as a fuse, in which case they may not actually be required to work more than once!
 

mbrooke

Batteries Not Included
Location
United States
Occupation
*
A newish tenant texts me to say she keeps blowing her circuit breaker. Now, this is an old unrenovated apartment with 15A only circuits. And she's got an 1875W blow dryer! That's over 15A no matter how you slice it, and as I understand code, you shouldn't have a device pulling a steady load over 80% of circuit rating, right? The 1875W rating seems expressly designed to keep just under 80% of 20A.

I've told her she needs to get a 1200w blow dryer. But my question is: how is this hazard even possible, isn't this the reason 20A receptacles and plugs exist, to keep this from happening? Why does the 1875W device not have a 20A plug that won't go in a 15A receptacle? Even if I had a 20A bath receptacle circuit, it would have made no difference, she was doing her hair in the bedroom!


Marketing. While running that dryer won't be drawing over 15amps, if that.

If the breaker keeps tripping you might want to change it, its possible over the years that its been tripped so many times by say space heaters being plugged into the same circuit that its just become "tired".
 

JFletcher

Senior Member
Location
Williamsburg, VA
Not all greater than 15 amp devices have a 20 amp plug. a few years ago, while researching a question for a post here I came across a 3000w commercial grade kitchen appliance that had 2 15 amp plugs on it. The plugs had to be run into receptacles of different circuits to achieve the 3000 watt rating.

While 6-20 plugs for 20 amp 240 volt circuits are pretty common on PTAC units and other equipment, I do not honestly remember the last time I saw a 5-20 plug on anything.
 

MAC702

Senior Member
Location
Clark County, NV
... I do not honestly remember the last time I saw a 5-20 plug on anything.
Some of my smaller welders and a plasma cutter have it, but then they also have adapters so they can also be plugged into a 5-15, which just makes the 5-20 useless since any 5-15 plug can go into a 5-20 receptacle. The prongs are the same ampacity, just a different configuration.
 
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