Go Back  DoItYourself.com Community Forums > Electrical, AC & DC. Electronic Equipment and Computers > Electrical - AC & DC
Reload this Page >

Moved Circuit to Sub Panel And Now It Blows the Subs Main Breaker

Moved Circuit to Sub Panel And Now It Blows the Subs Main Breaker

Reply

  #1  
Old 06-06-14, 11:13 AM
Member
Thread Starter
Join Date: Jun 2013
Posts: 5
Moved Circuit to Sub Panel And Now It Blows the Subs Main Breaker

I installed a sub panel next to my main panel because I was out of spaces in the main load center. I set the sub panel up off of a 50 amp breaker in the main. To install this 50 amp breaker I had to move one 20 amp tandem and another 20 amp single pole breaker to get space. 3 circuits total.

2 of the 3 had no issues and worked fine when moved to the subpanel. The third circuit is what is causing me strange issues. When I flip on its breaker in the sub panel it immediately blows the 50 amp breaker in the main panel. Its 20 amp breaker in the sub does not trip.

I am sure it is wired correctly and I moved all three of the wires to the sub (hot, neutral and ground).

What could be the cause of this? Should I try to move it back to the main panel and swap it with another breaker??


thanks in advance!
 
Sponsored Links
  #2  
Old 06-06-14, 11:48 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,979
Is it the single pole breaker that is tripping the 50 amp breaker or is it the tandem? Can you take a picture of your panel set up? Does your sub panel have a main breaker? Did you check voltages at the sub panel after you had everything connected? Is the 50 amp breaker as standard two pole?
 
  #3  
Old 06-06-14, 11:58 AM
Member
Thread Starter
Join Date: Jun 2013
Posts: 5
Because I have more space now, none of the circuits I moved are on tandems. All have regular 20a single pole breakers. The 50 amp breaker is tripping if i turn that particular circuit on in the sub panel. I have tried using different 20a breakers for the circuit, it does not affect the issue/

The sub panel does not have a main breaker. Its main breaker is the 50a one in the main (which is a standard QO double-pole.)



note the tandem in the sub was used temporarily until i got another 20 amp single. it is no longer there and was unrelated to the issue.
 
  #4  
Old 06-06-14, 12:05 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,979
Is the circuit that is tripping one of the ones you have spliced to an old cable at the bottom of the main panel? OR is it the one that goes to the octagon box connected to the UF cable?
 
  #5  
Old 06-06-14, 12:10 PM
Member
Thread Starter
Join Date: Jun 2013
Posts: 5
It is one of the ones that I spliced at the bottom of the main. I spliced two that way and one works fine. The other causes this problem
 
  #6  
Old 06-06-14, 01:51 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,979
Disconnect the splice, cap it off, turn it on and see if it still trips the 50 amp breaker. If not, the issue is the old circuit. If it does still trip, then something is wrong with your new 12/2 cable.

Have you done anything else in the house? Maybe changed out some receptacles in the kitchen? Why do you need more spaces?
 
  #7  
Old 06-06-14, 02:51 PM
Member
Join Date: Feb 2002
Location: port chester n y
Posts: 2,117
One possibility is that when this particular CB is closed it's creating a 240v short-circuit across the 50 a DPCB. The reason is that somewhere the "live" Conductor of this Branch-Circuit is x-connected to "live" conductor of a 2nd Branch-Circuit with a CB on the Service Leg opposite the Service Leg of CB that causes the problem.
 
  #8  
Old 06-06-14, 02:53 PM
Member
Thread Starter
Join Date: Jun 2013
Posts: 5
I should've mentioned that I did that when I installed the sub and noticed this issue, almost 2 weeks ago. Everything works fine without that circuit connected. So it is most definitely an issue with the circuit.
 
  #9  
Old 06-07-14, 04:37 AM
Member
Join Date: Jan 2014
Location: USA
Posts: 699
The circuit and 20 amp circuit breaker that is tripping , physically move it left or right one full 1" space . This will put that CB on the opposite phase . Now try it .

If it no longer trips , that indicates that some where in the house , that " hot " is connected to another " hot " that is on another CB . In the 1st loadcenter , it just happened that they ended up on the same phase . No problem was observed . When you added the sub panel , the " bad " circuit ended up on the opposite phase , so bad things happen when you turn that CB on .

If you see no change from moving the CB in question , replace the Romex between the 2 loadcenters and re-do the splice . Do a very close visual inspection .

Best of luck .

God bless
Wyr
 
  #10  
Old 06-07-14, 05:16 AM
Member
Join Date: Mar 2010
Location: USA
Posts: 2,850
Do not keep trying different things and turning the power on and seeing if the breaker trips. That will ruin the breaker and you might not find out until later when the breaker does not trip when you have a real overload.

Since you are still baffled about where the problem is, there is still the possibility (mentioned before) that the branch circuit in question has some wires crossed with and is being energized by a different branch circuit. So do the following:

Turn off the house main breaker.

Label and then unhook the wires of the problem circuit from its breaker.

Turn the power back on.

Measure voltage between one loose end and neutral and between that loose end and ground. Repeat for the other loose end. Finally measure voltage between the two loose ends.

Should you get 120 (or more) volts for any of these measurements then do not connect the wires to the breaker. You need to find out how the wire got energized and correct that problem first.

Although two branch circuits' cables can enter the same junction box up in the house, neither hots nor neutrals wires of different branch circuits may be interconnected there. As a result it is possible to have two bundles of neutral wires in a box. Circular branch circuits (a cable leaves the breaker box and is interconnected with various other cables up in the house including another cable that comes back down to the box) are not permitted.

If you get zero for all of the preceding measurements then make sure all appliances, lights, etc. on that circuit are unplugged or at least switched off. Use the ohms or continuity function to measure the resistance between the two loose ends and also between each loose end and neutral. They should all be near infinite ohms. (Less than infinite and more than two hundred ohms is good enough; that won't trip any breakers. Means you overlooked an appliance or doorbell transformer still connected.) Should you get near zero resistance then you need to find out why and correct that before reconnecting the wires to the breaker.
 

Last edited by AllanJ; 06-07-14 at 06:34 AM.
  #11  
Old 06-07-14, 05:21 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 11,979
Everything works fine without that circuit connected. So it is most definitely an issue with the circuit.
What area of the house does this circuit serve?
 
Reply

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


Thread Tools
Search this Thread
Display Modes
'