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 06-06-2014, 04:58 PM   #16
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,411
Share |
Default

Strange issue with sub panel installation


Is the original panel a GE?

__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is offline   Reply With Quote
Old 06-06-2014, 05:12 PM   #17
Licensed Pro
 
Join Date: Mar 2007
Location: SC
Posts: 1,535
Default

Strange issue with sub panel installation


Check your cable clamps... too tight can cause a short.
__________________
"Life is hard. Life is harder when you're stupid." John Wayne
HouseHelper is online now   Reply With Quote
Old 06-06-2014, 05:22 PM   #18
Member
 
Join Date: Aug 2009
Posts: 601
Default

Strange issue with sub panel installation


Quote:
Originally Posted by Jim Port View Post
Is the original panel a GE?
Looks like Square D.

Curious, where you going with it if it was GE ?
ritelec is offline   Reply With Quote
Old 06-06-2014, 05:27 PM   #19
Member
 
Join Date: Aug 2009
Posts: 601
Default

Strange issue with sub panel installation


I'm thinking the op found the issue.
ritelec is offline   Reply With Quote
Old 06-06-2014, 07:08 PM   #20
Member
 
Join Date: Sep 2012
Posts: 342
Default

Strange issue with sub panel installation


Quote:
Originally Posted by ritelec View Post
Interesting.

Sounds like that circ is back fed and as you close the connection at the breaker it trips the two pole feeder breaker.

That it also didn't trip in the main panel because it was possibly on the same legg.

You would have done it live, but you wired it and didn't get rapped, .

with that breaker off.
check to see if that circuits hot?

My best guess would be a short on that circuit plus a defective branch breaker.


Replace the branch breaker with another and see what happens. If that breaker trips its a short.
Jump-start is online now   Reply With Quote
Old 06-06-2014, 07:24 PM   #21
Member
 
Join Date: Oct 2010
Location: Cairns Australia
Posts: 2,379
Default

Strange issue with sub panel installation


Quote:
Originally Posted by mrules45 View Post
I had to move one 20 amp tandem and another 20 amp single pole breaker to get space. 3 circuits total.
1 - What loads are on these circuits that you have moved ?
2 - Did they work ok before the shift ?
3 - Can you turn off these breakers, and tell us what voltage is on the line side of these breakers,
A - measure reletive to neutral.
B - On the tandem measure between the two hots, as well as reletive to neutral.
Post your results.
4- Measure also on the load side for voltage.

You will need a volt meter for these measurements
Also are you confident you can do this safely ?
dmxtothemax is online now   Reply With Quote
Old 06-06-2014, 09:02 PM   #22
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,697
Default

Strange issue with sub panel installation


Quote:
Originally Posted by Robpo View Post
If the tandem breaker is the same brand as the other breakers(it looks like it might be different) I would shut off the 50 amp and turn all the others on and then turn the 50 on and see if one of the other breakers trip. I can't see anything wrong.
Not a smart way to trouble shoot.
__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is offline   Reply With Quote
Old 06-16-2014, 10:47 AM   #23
Newbie
 
Join Date: Jun 2014
Posts: 1
Default

Strange issue with sub panel installation


My guess - in the original panel, the two circuits on the tandem were on the same phase (because that's how a single tandem works). On the other end, they are shorted together. That would appear to work fine, even though the neutral could be overloaded. When you moved them over to the sub, you put them on opposite phases, and thus they would trip the 50A breaker.

The fix is to find out where they are shorted and fix it there. It may be a split receptacle where someone forgot to break the tab...
/mike
n1ist is offline   Reply With Quote
Old 06-16-2014, 05:20 PM   #24
Member
 
Join Date: Sep 2012
Posts: 342
Default

Strange issue with sub panel installation


The big thing here is that a 50amp breaker is tripping before a 20 in series. Something is very wrong. Either 2 circuits on the same leg are faulting simultaneously or the tandem is defective. Yes I know it could be that by chance the 50amp might have a faster magnetic trip curve over the 20, but still Id replace it just in case. After the short is found of course.
Jump-start is online now   Reply With Quote
Old 06-16-2014, 05:24 PM   #25
Member
 
Join Date: Oct 2010
Location: Cairns Australia
Posts: 2,379
Default

Strange issue with sub panel installation


Not unknown or wrong !
It's a thing known by many experienced electricians.
It's simply because there is more current available at the 50A breaker
because there's less things in the way to impedeed the current flow !
dmxtothemax is online now   Reply With Quote
Old 06-16-2014, 07:01 PM   #26
Member
 
Join Date: Sep 2012
Posts: 342
Default

Strange issue with sub panel installation


Quote:
Originally Posted by dmxtothemax View Post
Not unknown or wrong !
It's a thing known by many experienced electricians.
It's simply because there is more current available at the 50A breaker
because there's less things in the way to impedeed the current flow !
Assuming minimal loads and none of the loads pull substantially more current under a voltage sag 4000amps of fault current (assuming) on the tandem will also be seen at the 50amp breaker. The big breaker doesn't see more fault current. Impedance values are summed.


Electricians may see large breakers blow first but its more from either the natural variance in trip curves (very much the norm on breakers from different makers) on molded case breakers or the branch is defective.

Jump-start is online now   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
Mobile Home Electrical Panel Replacement rrolleston Electrical 2 01-28-2012 05:27 PM
Sub Panel GND and mixed 240/120 VAC branch curiousB Electrical 12 01-17-2012 10:49 AM
Passing wire to another panel theatretch85 Electrical 5 09-20-2009 11:09 PM
Replacing 2 Sub Panels with 1 Larger Panel GuitarJack Electrical 7 08-25-2009 08:43 PM
Multiple Sub Panel Installation Handyman2007 Electrical 26 12-31-2007 05:47 PM




Top of Page | View New Posts

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