Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 02-02-2009, 08:23 AM   #16
Electrician's Helper
 
Pudge565's Avatar
 
Join Date: Jan 2008
Location: Pennsylvania
Posts: 202
Rewards Points: 150
Send a message via AIM to Pudge565
Default

Hair dryer question


Quote:
Originally Posted by KE2KB View Post
Actually, a hairdryer is a mainly resistive load, so if the voltage drops, so does the current, and thus the wattage.

FW
Oh yes thanks for correcting me.

__________________
There is no such thing as a stupid question, but there is such a thing as an ignorant person, with a question, trying to learn.
Pudge565 is offline   Reply With Quote
Old 02-02-2009, 08:32 AM   #17
Member
 
Join Date: Oct 2008
Location: New Jersey, USA
Posts: 1,202
Rewards Points: 500
Default

Hair dryer question


Quote:
Originally Posted by Yoyizit View Post
Had a customer once where it took a good ten minutes before the 1875W tripped the 15A breaker.
I suppose that if it is very cold where the breaker is located, the time/temp curve would be changed, and it would take longer to trip.
My panel is located (as most are) on the foundation wall. It's probably around 10C at the panel right now. Now this has me interested in looking up the curve for the CH breakers.

FW
__________________

KE2KB is offline   Reply With Quote
Old 02-02-2009, 11:40 AM   #18
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Hair dryer question


Quote:
Originally Posted by KE2KB View Post
looking up the curve for the CH breakers.FW
Finding them on the Internet is like pulling teeth, but they are full of interesting info: The one-cycle trip time, the minimum trip time regardless of current (probably limited by the inertia of the gizzards) and the current at which the thing will never trip.
Part of the curve follows an IT relationship, other parts do not. Underneath this strange curve are asymptotes representing ideal, design-goal performance, but they are not very apparent by looking. One trip mechanism response kind of blends into the next one.

The 20A CB I took apart had a 2w, 2" long, strange looking resistive wire in it to handle the IT part; I couldn't readily see how they did the magnetic part.

Last edited by Yoyizit; 02-02-2009 at 12:31 PM.
Yoyizit is offline   Reply With Quote
Old 02-02-2009, 06:08 PM   #19
Member
 
Join Date: Oct 2008
Location: New Jersey, USA
Posts: 1,202
Rewards Points: 500
Default

Hair dryer question


Quote:
Originally Posted by Yoyizit View Post
Finding them on the Internet is like pulling teeth, but they are full of interesting info: The one-cycle trip time, the minimum trip time regardless of current (probably limited by the inertia of the gizzards) and the current at which the thing will never trip.
Part of the curve follows an IT relationship, other parts do not. Underneath this strange curve are asymptotes representing ideal, design-goal performance, but they are not very apparent by looking. One trip mechanism response kind of blends into the next one.

The 20A CB I took apart had a 2w, 2" long, strange looking resistive wire in it to handle the IT part; I couldn't readily see how they did the magnetic part.
Do all CB's use both temp and magnetic elements?
I recall that magnetics were always more accurate, and would trip at the same current regardless of ambient temp.
The old FPE I had were strictly a thermal device, so if the panel were outside in the middle of winter, breakers would require a lot more current before they trip.

Somehow, I have the idea that CH are magnetic, but then I don't really understand that much about the innards of CB's.

FW
__________________

KE2KB is offline   Reply With Quote
Old 02-02-2009, 08:11 PM   #20
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Hair dryer question


http://en.wikipedia.org/wiki/Circuit_breaker
Yoyizit is offline   Reply With Quote
Old 02-02-2009, 08:24 PM   #21
Member
 
Join Date: Dec 2008
Location: Southern Wisconsin
Posts: 171
Rewards Points: 150
Default

Hair dryer question


KE2KB:

I've been reading thru this thread and I decided to do some investigating regarding the hair dryer question. My wife has a 1875 watt hair dryer too so I took an amp draw reading when it was on high. The voltage was 120 and the amp draw turned out to be 13.

I also checked this out using ohm's law. The voltage was 120 and the resistance of the hair dryer was 9.3 ohms. Current=voltage/resistance. Current turned out to be 12.9 volts. I was getting 13 with my clamp on meter.
Steelhead is offline   Reply With Quote
Old 02-02-2009, 08:29 PM   #22
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Hair dryer question


Quote:
Originally Posted by Steelhead View Post
the resistance of the hair dryer was 9.3 ohms. Current=voltage/resistance.
Only if hot resistance = cold resistance. For Nichrome it pretty much does, not so for tungsten.
Yoyizit is offline   Reply With Quote
Old 02-02-2009, 09:21 PM   #23
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,864
Rewards Points: 2,032
Default

Hair dryer question


Quote:
Originally Posted by Steelhead View Post
KE2KB:

I've been reading thru this thread and I decided to do some investigating regarding the hair dryer question. My wife has a 1875 watt hair dryer too so I took an amp draw reading when it was on high. The voltage was 120 and the amp draw turned out to be 13.

I also checked this out using ohm's law. The voltage was 120 and the resistance of the hair dryer was 9.3 ohms. Current=voltage/resistance. Current turned out to be 12.9 volts. I was getting 13 with my clamp on meter.
So the actual wattage of this "1875 watt" hair dryer was only 1560 watts.
False advertising?
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 02-02-2009, 09:47 PM   #24
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Hair dryer question


Quote:
Originally Posted by Speedy Petey View Post
So the actual wattage of this "1875 watt" hair dryer was only 1560 watts.
False advertising?
Well, this "mistake" is in favor of the seller, since more power = more money for the seller.

And, does the seller ever make "mistakes" not in his favor (which he should, approx. half the time)?
Yoyizit is offline   Reply With Quote
Old 02-02-2009, 10:03 PM   #25
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,864
Rewards Points: 2,032
Default

Hair dryer question


I really don't think the word "mistake" is appropriate here.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 02-02-2009, 10:22 PM   #26
Idiot Emeritus
 
Join Date: Mar 2008
Location: Fernley, Nevada (near Reno)
Posts: 1,618
Rewards Points: 1,030
Default

Hair dryer question


Sorta like the 5 HP air compressor....Runs on standard house current.

If I figured out how to get 5 HP out of a 20 amp 120 volt circuit, I bet I wouldn't be building air compressors!

Rob
micromind is offline   Reply With Quote
Old 02-02-2009, 10:34 PM   #27
Member
 
joed's Avatar
 
Join Date: Mar 2005
Location: Welland, Ontario
Posts: 7,854
Rewards Points: 2,502
Blog Entries: 4
Default

Hair dryer question


Quote:
Originally Posted by Speedy Petey View Post
So the actual wattage of this "1875 watt" hair dryer was only 1560 watts.
False advertising?
If you use the high limit of the electrical grid of 130 volts and the 9.3 measured reading then you get 1817 watts. It's all relative to how you rate them.
Same thing happens with compressors. They over rate the HP by stating it as PEAK HP. It's better now for compressors since the manufactures lost a law suit for stating the peak HP instead of the continuous running HP.

http://www.lawcash.com/attorney/3392...nc-lawsuit.asp
joed is online now   Reply With Quote
Old 02-03-2009, 09:49 AM   #28
Member
 
Join Date: Oct 2008
Location: New Jersey, USA
Posts: 1,202
Rewards Points: 500
Default

Hair dryer question


I recall way back when stereo amplifiers were allowed to be rated for "peak music power", which is much higher than trur RMS @ 1Khz.
When I needed to purchase a sub-amp for my Subaru Forester, I had to buy an 1100W, because that's the smallest I could find.
What would I want 1100W in my small SUV for?

My sister bought an 1875W hair dryer from Harmon yesterday for under $25. Looks decent. Has the GFCI (actually, I think there's another term for these devices) plug of course.
I'm still going to add receptacle on a 20A branch to her room for the dryer.

FW

__________________

KE2KB is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dryer exhaust question KC Brick Layer Plumbing 3 12-08-2008 08:47 AM
Electric Dryer wiring/plug question SpaceCrawler Electrical 6 08-26-2008 04:33 PM
Question about dryer venting jimithing78 HVAC 10 08-26-2008 11:37 AM
Dryer Vent Question jlaky2000 HVAC 2 03-13-2008 08:22 PM
Dryer exhaust question Felipon Appliances 6 02-03-2008 11:29 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.