Testing A Breaker - Electrical - DIY Chatroom Home Improvement Forum


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

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

Reply
 
Thread Tools Display Modes
Old 05-05-2010, 03:42 PM   #1
Member
 
Join Date: Oct 2009
Location: Missouri
Posts: 37
Rewards Points: 25
Default

Testing a breaker


Hi,

I have a 20 amp square D home line circuit breaker that trips very intermittently, seemingly without any excess load. The circuit serves 6 outlets with one computer that draws ~300 watts and 160 watts of lighting.

The breaker is 6 months old but I can't think of other issues in the circuit so I would like to know if this is the problem. I could just change it and hope for the best but because it trips so rarely I won't know for weeks if the problem is solved. Is there a way to test the functionality of said breaker?

Thanks,

Thomas

Advertisement

trosenda is offline   Reply With Quote
Old 05-05-2010, 05:49 PM   #2
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Testing a breaker


Quote:
Originally Posted by trosenda View Post
Is there a way to test the functionality of said breaker?
First post the trip curve for your particular breaker. You're looking for the trip time at 40A and the quickest trip time, regardless of how high the current is.

Advertisement


Last edited by Yoyizit; 05-05-2010 at 06:13 PM.
Yoyizit is offline   Reply With Quote
Old 05-05-2010, 06:20 PM   #3
Member
 
Join Date: Mar 2007
Location: Eighty Four, Pa.15330
Posts: 1,403
Rewards Points: 804
Default

Testing a breaker


For the $10 ,change the circuit breaker,and see what goes.
bobelectric is offline   Reply With Quote
Old 05-05-2010, 06:35 PM   #4
Sparkaholic
 
Join Date: May 2010
Location: Miami, Florida
Posts: 192
Rewards Points: 150
Send a message via Yahoo to sparks1up
Default

Testing a breaker


I have to agree with Bob! Replace the breaker, if it still trips you may have a problem that requires a professional to troubleshoot! If it doesn't you saved yourself the price of a service call!
sparks1up is offline   Reply With Quote
Old 05-05-2010, 06:36 PM   #5
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Testing a breaker


Quote:
Originally Posted by bobelectric View Post
For the $10 ,change the circuit breaker,and see what goes.
And if that fixes it, it could have been the breaker or just a bad connection.
Yoyizit is offline   Reply With Quote
Old 05-05-2010, 08:55 PM   #6
Member
 
joed's Avatar
 
Join Date: Mar 2005
Location: Welland, Ontario
Posts: 8,362
Rewards Points: 3,518
Blog Entries: 4
Default

Testing a breaker


Swap the wire with another breaker of the same value. See which one if any trips.
__________________
Do not PM with questions that can be asked in a forum. I will not respond.
joed is offline   Reply With Quote
Old 05-05-2010, 09:17 PM   #7
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 8,017
Rewards Points: 2,832
Default

Testing a breaker


Given this info by the OP

Quote:
Originally Posted by trosenda View Post
Hi,

I have a 20 amp square D home line circuit breaker that trips very intermittently, seemingly without any excess load. The circuit serves 6 outlets with one computer that draws ~300 watts and 160 watts of lighting.
We are looking at less than 500 watts on a breaker that will handle over 4 times that amount for a long time.

How about posting something useful instead of unnecessarily technical like this? What does the 40 amp trip time have to do with the OPs situation?

Quote:
Originally Posted by Yoyizit View Post
First post the trip curve for your particular breaker. You're looking for the trip time at 40A and the quickest trip time, regardless of how high the current is.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is online now   Reply With Quote
Old 05-05-2010, 09:41 PM   #8
Member
 
Join Date: May 2009
Location: Brooklyn, New York (NYC)
Posts: 1,124
Rewards Points: 500
Thumbs up

Testing a breaker


Quote:
Originally Posted by bobelectric View Post
For the $10 ,change the circuit breaker,and see what goes.
Or it could be failing insulation (on old wiring.) Which is done with a "Megger" (Megohm meter.) p.s: this post is addressed to the OP!!
spark plug is offline   Reply With Quote
Old 05-06-2010, 11:24 AM   #9
Member
 
Join Date: Oct 2009
Location: Missouri
Posts: 37
Rewards Points: 25
Thumbs up

Testing a breaker


Thanks thats not a bad suggestion, however the entire circuit, wire and all is <6 months old. I guess, as others have said, I will start by changing the breaker. Trouble is, I won't have confirmed that was the problem until weeks have passed and I don't get another trip.

I hate to get a trip on this circuit because the computer is plugged into it and it needs to always be on.

After I change the breaker is there a way to test the one I have removed to determine if it was the problem?
trosenda is offline   Reply With Quote
Old 05-06-2010, 12:16 PM   #10
Just call me Andrew
 
Join Date: Mar 2009
Location: Albany, NY
Posts: 2,258
Rewards Points: 1,012
Default

Testing a breaker


Quote:
Originally Posted by joed View Post
Swap the wire with another breaker of the same value. See which one if any trips.
This is quick and free. I'd do this before changing the breaker. If the other circuit trips after changing them, you know the breaker was the problem. If they both stop tripping, there was probably a loose connection.

Might want to tighten up all the connections on your neutral bar too while you're in there.
__________________
Andrew

secutanudu is offline   Reply With Quote
Old 05-06-2010, 06:19 PM   #11
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Testing a breaker


Quote:
Originally Posted by Jim Port View Post
How about posting something useful instead of unnecessarily technical like this? What does the 40 amp trip time have to do with the OPs situation?
I hope at least some of my posts are useful to some of the OPs.

The OP said he wants to test the breaker. Getting technical is necessary.

In general the trip time for 2x rated current is about a minute.
He can load the circuit with 4 ea. 10A loads and time how long it takes to trip.
#12 copper at 40A will take about 10 minutes to melt, if it will ever melt at 40A, so you don't need extraordinary care to run this test.

For tripping the breaker in a half cycle of 60 Hz, I don't recommend the OP should do this.



Mr. Port, you know stuff that I don't know. I guess I'm OK with that.

I have always been curious and I have always read a lot, so. . .
I probably know stuff that you don't know. Your choice is to be OK with that, or not.

If this is not OK with you, you are allowing me to raise your blood pressure.
Why would you allow me to have that power over you?

Last edited by Yoyizit; 05-06-2010 at 06:45 PM.
Yoyizit is offline   Reply With Quote
Old 05-06-2010, 08:05 PM   #12
Tool Geek
 
PaliBob's Avatar
 
Join Date: Jun 2008
Location: Pacific Palisades CA
Posts: 2,546
Rewards Points: 2,072
Cool

Testing a breaker


A contractor that does a lot of work in industry may have a C/B tester.
I am in possession of a 25 year old C/B Tester made by EIL, but while I think they are now out of business, there are other sources.

The one I have was used by my old contractor boss when I filled in as a Temp. The reason I have it now is that since he retired, he wants me to put it on E-Bay for him.
Attached Thumbnails
Testing a breaker-eil-1.jpg   Testing a breaker-eil-2.jpg   Testing a breaker-eil-3.jpg   Testing a breaker-eil-4.jpg  
__________________
Disclaimer
& Stay Safe
.....Bob Lavery
PaliBob is offline   Reply With Quote
Old 05-06-2010, 08:30 PM   #13
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

Testing a breaker


That box is probably full of transformers.

With a clamp-on ammeter, I guess the OP could use one of those Weller two post soldering guns; they probably deliver 150A to the tip.
Yoyizit is offline   Reply With Quote
Old 05-06-2010, 09:50 PM   #14
Tool Geek
 
PaliBob's Avatar
 
Join Date: Jun 2008
Location: Pacific Palisades CA
Posts: 2,546
Rewards Points: 2,072
Default

Testing a breaker


Quote:
Originally Posted by Yoyizit View Post
That box is probably full of transformers.......
Yep on the Xmfer, this puppy must weigh > 50lb
and the Power cord has a 15 Amp plug

It has some sophisticated test circuity to measure trip magnitude and time.

If the OP lived around here it would be fun to play with his C/B and compare it to one off the shelf.

.
Attached Thumbnails
Testing a breaker-eil-5-1.jpg  
__________________
Disclaimer
& Stay Safe
.....Bob Lavery

Last edited by PaliBob; 05-06-2010 at 09:55 PM. Reason: sp
PaliBob is offline   Reply With Quote
Old 05-07-2010, 03:27 AM   #15
" Euro " electrician
 
frenchelectrican's Avatar
 
Join Date: Apr 2006
Location: WI & France { in France for now }
Posts: 5,369
Rewards Points: 2,000
Default

Testing a breaker


Bob.,

I do keep a circuit breaker tester with me and I did use it from time to time and to the other readers if this is a transfomer and the answer is Oui { yes } also with ampmeter to read the current drawage to see excatly where it will fail or not.

Those unit are not cheap they are serveral thousand Euros { Dollars } but it worth it when you supect bad breakers.

Merci,Marc

Advertisement

frenchelectrican is offline   Reply With Quote
Reply

Tags
faulty breaker


Thread Tools
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
20 amp GFCI breaker pops when pool pump is turned on. jagrunner Electrical 11 03-19-2010 05:31 PM
small voltage on circuit with breaker off jasonmechler Electrical 3 08-24-2009 09:52 AM
Sq D Trillaint Breaker problem jmreynol Electrical 3 04-28-2009 08:06 PM
20 Amp Breaker tripping with GFCI panhandlion Electrical 7 12-12-2007 09:59 PM
Testing a circuit breaker? redline Electrical 1 06-29-2006 03:44 PM




Top of Page | View New Posts