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KE2KB 02-01-2009 07:53 PM

Hair dryer question
 
Good evening;
I'm curious; If a hair dryer is rated at 1875 Watts, then it should draw 16A.
That should mean that it would come with a 20A plug, since it will trip a 15A breaker, right?

If this is true, then someone must be playing games with the public. I have never seen a hair dryer with anything except a 15A plug or 15A GFCI plug.
So, what gives? Is the power rating just a selling point?

Reason I am asking this is that my sister needs a new one, and all she can find are 1875 Watts. I told her that she will not be able to use it on the highest setting, because the receptacle where she usually uses it is on a 15A circuit.
I am planning to either replace the wiring to the specific receptacle where she uses the dryer the most (it's not in the bathroom), or add a completely new receptacle on a 20A circuit that doesn't have any continuous loads.
So, if she buys the 1875 Watt model tomorrow, will she still be able to use it on the 15A circuit, with 15A receptacle if she doesn't use the highest setting?

I am aware that the bathroom is required to have 20A GFCI circuit. Ours does not, but I plan to rewire someday. Thing is, she uses the thing in her bedroom anyway. I assume I won't need a GFCI there, but maybe an AFCI?

Thanks for your help/advice.

FW

Gary_602z 02-01-2009 08:05 PM

Would a 16a draw trip a 15 amp breaker? Get your meter out. In the mean time maybe she could run it on a lower setting.

Gary

KE2KB 02-01-2009 08:27 PM

Quote:

Originally Posted by Gary_602z (Post 223343)
Would a 16a draw trip a 15 amp breaker? Get your meter out. In the mean time maybe she could run it on a lower setting.

Gary

Actually, I think that 16A would trip the 15A C&H breaker, after a few minutes. C&H has the reputation of being very sensitive.
I don't have a meter capable of reading 16A.
I only wish that the electrician who wired the room hadn't cheaped out and run #14/2. I always use 12/2 for my work, even if it's a 15A branch, with hopes of upgrading to 20A someday.

FW

micromind 02-01-2009 08:46 PM

I realize your breaker is CH, I don't have CH trip curves handy, but according to the Square D book, a QO 15 amp breaker will hold 16 amps anywhere from 200 seconds (3 minutes) to indefinately.

A 14/2 NM will have no problem with 16 amps continuously.

If the voltage at the main breaker is exactly 120, it'll be a bit less at the receptacle, therefore the amperage will be less as well. If the 14/2 is 50' from the panel to the receptacle, there will be about 4 volts drop in the wire. Starting at 120, this will result in about 15.1 amps.

Almost any 15 amp breaker will hold 15.1 amps continuously.

Rob

Steelhead 02-01-2009 08:52 PM

Quote:

Originally Posted by KE2KB (Post 223352)
Actually, I think that 16A would trip the 15A C&H breaker, after a few minutes. C&H has the reputation of being very sensitive.
I don't have a meter capable of reading 16A.
I only wish that the electrician who wired the room hadn't cheaped out and run #14/2. I always use 12/2 for my work, even if it's a 15A branch, with hopes of upgrading to 20A someday.

FW

I could be wrong on this but I don't think the hair dryer will draw 1875 watts continously. I think there is a thermostat in the dryer that cycles the power so the hair dryer doesn't burn up. Again I could be wrong on this. I thought I read about the thermostat in a magazine once.

KE2KB 02-01-2009 09:01 PM

Quote:

Originally Posted by micromind (Post 223366)
I realize your breaker is CH, I don't have CH trip curves handy, but according to the Square D book, a QO 15 amp breaker will hold 16 amps anywhere from 200 seconds (3 minutes) to indefinately.

A 14/2 NM will have no problem with 16 amps continuously.

If the voltage at the main breaker is exactly 120, it'll be a bit less at the receptacle, therefore the amperage will be less as well. If the 14/2 is 50' from the panel to the receptacle, there will be about 4 volts drop in the wire. Starting at 120, this will result in about 15.1 amps.

Almost any 15 amp breaker will hold 15.1 amps continuously.

Rob

There will be several other devices, including a 27" TV on the same branch.
I told my sister to avoid using the highest setting until I have a chance to upgrade the situation.

Before the 42 position C&H panel was installed (with upgrade from 100A to 200A), we had an FPE. Those breakers weren't worth a dime, were completely unreliable, and dangerous. The upgrade was performed when we had an addition put on the upstairs.
Like I said though; if I had wired the new addition, I would have used 12/2 and run 20A branches. As it stands, they ran two 20A (12/2) branches for the AC units, and only one 14/2, 15A for other receptacles in two rooms. IMO, this is not adequate. But perhaps because each room already had receptacles, and the addition was only making these rooms larger, the electrician did not feel the need for more capacity.
It did pass inspection though.

FW

Pudge565 02-01-2009 09:06 PM

Quote:

Originally Posted by micromind (Post 223366)
I realize your breaker is CH, I don't have CH trip curves handy, but according to the Square D book, a QO 15 amp breaker will hold 16 amps anywhere from 200 seconds (3 minutes) to indefinately.

A 14/2 NM will have no problem with 16 amps continuously.

If the voltage at the main breaker is exactly 120, it'll be a bit less at the receptacle, therefore the amperage will be less as well. If the 14/2 is 50' from the panel to the receptacle, there will be about 4 volts drop in the wire. Starting at 120, this will result in about 15.1 amps.

Almost any 15 amp breaker will hold 15.1 amps continuously.

Rob


Accually if wattage remains the same and voltage drops amerage will increase. Due to the fact that I=P/E so 2400 watts on a 240 volt and 120 volt circuit. So 2400/240=10amps now 2400/120=20amps.

Speedy Petey 02-01-2009 09:16 PM

I can only assume the manufacturers are doing the same thing as with GMRS radios when they claim 20-30 miles when they typically only do 2-3 miles tops.



Quote:

Originally Posted by KE2KB (Post 223352)
I always use 12/2 for my work, even if it's a 15A branch, with hopes of upgrading to 20A someday.

I have to say, I see NO point in this philosophy. WHY "upgrade" the circuit "someday"??? Do it now. :thumbsup:
If you run 12 use a 20A breaker. If you run 14 use a 15. Except for long runs to counter voltage drop there is NO reason to use a 15A breaker on #12. :no:

KE2KB 02-01-2009 09:58 PM

Quote:

Originally Posted by Speedy Petey (Post 223385)
I can only assume the manufacturers are doing the same thing as with GMRS radios when they claim 20-30 miles when they typically only do 2-3 miles tops.




I have to say, I see NO point in this philosophy. WHY "upgrade" the circuit "someday"??? Do it now. :thumbsup:
If you run 12 use a 20A breaker. If you run 14 use a 15. Except for long runs to counter voltage drop there is NO reason to use a 15A breaker on #12. :no:

Sometimes I cannot rewire an entire branch, so I run 12/2 from the panel to a J-box and re-connect some of the old wiring into the new. I am working in an 80yr old house, and trying to get rid of the worst first.
I hope this is only a temporary situation<g>
Eventually, I would like to have all the receptacles wired with 12/2 on 20A branches, and lighting with 14/2 on 15A branches.

Since this house was wired 80 years ago, there are branch circuits with lighting and receptacles. That was back when no one had appliances drawing 15A or more!

FW

KE2KB 02-01-2009 10:03 PM

Quote:

Originally Posted by Speedy Petey (Post 223385)
I can only assume the manufacturers are doing the same thing as with GMRS radios when they claim 20-30 miles when they typically only do 2-3 miles tops.

Sorry; I didn't even notice this part of your post:
Being a HAM, I understand that logic. It's the 'more is better' philosophy.
I've had trouble getting more than a few miles on 2m with 5W into a 5/8 whip, and then I have made contacts over 200 miles with the same radio and antenna from the Catskill mtns!

That's not to say that using the 1875 watt hair dryer on top of the Catskill mtns will dry your hair any faster than it will at sea level, but you know what I mean:jester:

FW

joed 02-01-2009 10:04 PM

1875 is best case marketing number. It is likely that the dryer doesn't draw the full 1875 when used. If they do the test with maximum allowable voltage of 130 volts and you only have 110 volts you won't be drawing the full watts.

KE2KB 02-01-2009 10:04 PM

Quote:

Originally Posted by Pudge565 (Post 223379)
Accually if wattage remains the same and voltage drops amerage will increase. Due to the fact that I=P/E so 2400 watts on a 240 volt and 120 volt circuit. So 2400/240=10amps now 2400/120=20amps.

Actually, a hairdryer is a mainly resistive load, so if the voltage drops, so does the current, and thus the wattage.

FW

Scuba_Dave 02-01-2009 10:07 PM

I had the same problem & my house is from the 50's
And they top wired instead of wiring from the basement
So I am adding outlets on some walls that do not have outlets
The 12a vacuum was a problem

My wife actually used her hair dryer in another room on high for hair drying. The bathroom circuit was extended off the rest of the house & would not handle much load. Since I had easy access & had to have plumbing done (wall ripped out) it made sense to run a dedicated 20a fairly quickly

KE2KB 02-01-2009 10:24 PM

Quote:

Originally Posted by Scuba_Dave (Post 223418)
I had the same problem & my house is from the 50's
And they top wired instead of wiring from the basement
So I am adding outlets on some walls that do not have outlets
The 12a vacuum was a problem

My wife actually used her hair dryer in another room on high for hair drying. The bathroom circuit was extended off the rest of the house & would not handle much load. Since I had easy access & had to have plumbing done (wall ripped out) it made sense to run a dedicated 20a fairly quickly

These darn power hungry appliances<g>
I just finished installing a new 20A branch to a receptacle in my upstairs hall, mostly for the vacuum, which can draw up to 12A.
I will install a new receptacle for my sister in her bedroom off the same branch, since it is extremely unlikely that both the vacuum and hair dryer will be used at the same time.
When I added the receptacle in the hall, I pig-tailed to 30ft of 12/2 from it to a j-box in my closet with the cable coiled up. I always plan ahead<g>

I still have to add at least one more 20A line upstairs for the bathroom.
I've got a closet wall that lies directly above a wall downstairs, and have been using it to pull power, CATV, and CAT5 cables. It's great to have a closet where I can rip out walls and don't have to repair right away!

FW

Yoyizit 02-02-2009 08:17 AM

Had a customer once where it took a good ten minutes before the 1875W tripped the 15A breaker.


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