Main breaker keeps popping

Reply

  #1  
Old 06-27-05, 12:18 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Main breaker keeps popping

This summer the main (100 amp) circuit breaker for my house is popping off routinely. Seems three ACs, (an 8000 BTU, and two ~6000 BTU units) run simultaneously is enough to do it. The only other major draw is an old, dying side by side fridge.

The thing is, last year I could run as much, I'd only pop the main if the electric oven was on too. This year it happens even with the oven off. And I can't even immediately reset the breaker, it's too warm, I need to let it cool 5 minutes before it will stick a reset. On a 100 amp breaker from 3 modest ACs and a fridge?

What could be the issue? I'd understand if they were on a single circuit and that was popping, but the 100 amp main? Could my dying fridge be surging that much when the compressor kicks in? To the same degree as what used to require a 50 amp electric stove?

Any ideas?
 
Sponsored Links
  #2  
Old 06-27-05, 12:32 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Your service is overloaded. My guess is that this summer is a bit hotter than last summer, or maybe you have the ACs set a bit lower. And yes, the dying fridge could be contributing to the problem.

Do you have other large electrical loads? For example, is your water heater electric? Is your clothes dryer electric?

I'm afraid you're going to have to turn off at least one of the ACs until you get a service upgrade.
 
  #3  
Old 06-27-05, 12:32 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Circuit breakers trip on 2 things: overcurrent or overtemperature. From your description, something is wrong and causing the breaker to overheat, which makes it trip.

The overheating could be caused by a bad breaker, or by a loose connection at the breaker. This could indicate that the bus bars that the breaker connects to are damaged. (a loose connection can cause this, by arcing and heating). If the bus bars are damaged, then fixing this will require replacing your breaker panel.

The problems that you describe can represent a fire hazard.

In general, diagnosing and fixing problems with the main breaker are jobs for professionals. I suggest that you call an electrician immediately.

-Jon
 
  #4  
Old 06-27-05, 01:04 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Thanks for your responses.

Originally Posted by John Nelson
Do you have other large electrical loads? For example, is your water heater electric? Is your clothes dryer electric?
No, just the ACs, fridge, and stove. The others are gas. But it's happening even with the stove off.

Originally Posted by winnie
Circuit breakers trip on 2 things: overcurrent or overtemperature. From your description, something is wrong and causing the breaker to overheat, which makes it trip.

The overheating could be caused by a bad breaker, or by a loose connection at the breaker. This could indicate that the bus bars that the breaker connects to are damaged. (a loose connection can cause this, by arcing and heating). If the bus bars are damaged, then fixing this will require replacing your breaker panel.

The problems that you describe can represent a fire hazard.

In general, diagnosing and fixing problems with the main breaker are jobs for professionals. I suggest that you call an electrician immediately.

-Jon
Couple of follow up questions.

If the old fridge is part of the problem, and after replacing it I was no longer tripping the breaker, are you saying that a hidden problem may likely still exist, and I may still be advised to have work done? Will the electrician's be able to test and identify the problem without the high load?

Are the sorts of repairs you are envisioning sufficiently expensive to justify upgrading the amperage at that time, or might it be as simple as replacing a worn breaker?

Thanks folks.
 
  #5  
Old 06-27-05, 01:33 PM
Member
Join Date: Jun 2002
Location: Brethren, Mi
Posts: 1,648
It could conceivably be possible that all the units are running off of one leg of the service too. I went to a place and on a sub they had 200 ft of number 6, drawing 49A down one and 1 (one 100 watt light) down the other. One of the loads was a small cooler, V drop to the max and it would trip when the cooler start. Changed the cooler to the other leg and presto.
 
  #6  
Old 06-27-05, 04:48 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Think hard to see if there are any other electrical loads that you are not telling us about, eg. a well pump or sewage pump; perhaps an electric space heater somewhere, etc. Too much load will cause the main breaker to trip.

The loads that you have listed are quite small. For example, an older fridge might take 4A at 120V, and the ACs might take 10-15A at 120V. I presume that you have some lights on, possibly a TV or some such, but still it seems that your worst case loading is perhaps 40A at 120V. This should not be tripping a 100A breaker unless you get unlucky and _everything_ tries to start up at the same time, and _everything_ is on a single 120V leg of your 240V service.

The fact that the fridge is _not_ tripping its branch circuit breaker suggests to me that the fridge is _not_ the culprit.

But if you replace the fridge, and the breaker stops tripping, then I would still believe that you have a problem, one that will keep getting worse until it shows up again.

An electrician would need to evaluate the problem, but if the problem is with the breaker bus bars, then you will need to replace the panel. At this point a service upgrade might make sense, but you would need to evaluate the prices involved.

-Jon
 
  #7  
Old 06-28-05, 06:56 AM
Member
Join Date: Jan 2005
Location: North Virginia
Posts: 192
Pretty much everything that has been said is true and should be considered, but also, as appliances age (like a dying fridge or a window shaker), they will become less efficient and start to draw more current. This is especially evident at peak draw periods. When was the last time you cleaned the coils on the refrigerator? I have seen stats that show a normal fridge pulls 3 times it average load at start up and in severe cases (dirty coils, in a hot room, while defrosting, etc) one fridge pulled 50 times the average running load while it was starting.

I would recommend doing a little maintenance on your appliances as well as getting an electrician to check it out.
 
  #8  
Old 06-28-05, 07:57 AM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
I think the fridge does play a major role. I recently moved it to a shared circuit, but even when it was on a 20 amp dedicated line it would dim lights on other circuits when the compressor cycled. The thing has got to be near 30 years old, and I'm sure the coils are a mess. It's gonna be outta here real soon.

Before I bring in an electrician, is it feasible for me to change out the main breaker? I've changed normal breakers before, but naturally I turned off the main first. How does one turn off the power to change the main breaker, or is there a trick?

Thanks!
 
  #9  
Old 06-28-05, 08:36 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
"is it feasible for me to change out the main breaker"

Feasible, yes. Practical? Probably not. The meter needs to be pulled, and you need to take special care that all connections are tightened properly.

Best left to a professional.
 
  #10  
Old 06-28-05, 09:35 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
"lights dim on other circuits". This means one of two things: either the fridge is drawing a tremendous amount of juice _or_ you have a bad connection in your main supply (anywhere from the transformer to where your main breaker hits the bus) such that normal amounts of current flow cause excessive voltage drop.

If lights dim on other circuits when the fridge compressor starts, but not when the AC compressors start, than this implicates the fridge. but if anything serious starting on any circuit makes lights dim on the same leg of your service, then this implicates the main.

-Jon
 
  #11  
Old 06-28-05, 10:32 AM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Originally Posted by racraft
"is it feasible for me to change out the main breaker"

Feasible, yes. Practical? Probably not. The meter needs to be pulled, and you need to take special care that all connections are tightened properly.

Best left to a professional.
Yup, over my head.

Originally Posted by winnie
"lights dim on other circuits". This means one of two things: either the fridge is drawing a tremendous amount of juice _or_ you have a bad connection in your main supply (anywhere from the transformer to where your main breaker hits the bus) such that normal amounts of current flow cause excessive voltage drop.

If lights dim on other circuits when the fridge compressor starts, but not when the AC compressors start, than this implicates the fridge. but if anything serious starting on any circuit makes lights dim on the same leg of your service, then this implicates the main.

-Jon
Okay. So should I just replace the fridge (which I plan to do anyway) and if all is well after that, leave well enough alone? Or should I bring in an electrician now so the fridge can be observed in action? Obviously money (for unnecessary electrical work) is an issue.

Thanks again.
 
  #12  
Old 06-28-05, 10:59 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
You should definitely replace the fridge. New fridges are so much more electrically efficient than old fridges, that you could easily save $100 a year in electricity costs (well, $40 to $150). A new high efficiency fridge should pay for itself pretty quickly.

My best guess is that you have a problem that requires immediate investigation by an electrician. But I'm also paranoid about such things.

What you can do is use the other loads on the circuits to run a couple of tests.

1) Map out your electrical system. Figure out which outlet is connected to which breaker.

2) Look at the panel circuit diagram and figure out which breakers connect to which bus.

3) Plug the fridge in to a difference circuit on the _opposite_ bus. See if this fixes the problem.

4) Take the fridge and plug it in to a different circuit, but on the same bus as the original circuit. See if the problem comes back.

If the problem is localized to a single bus, but not a single circuit, then you can be darn certain that you have a problem with your supply, and if the breaker is getting _hot_ then the problem is probably with the breaker.

-Jon
 
  #13  
Old 06-28-05, 11:57 AM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Okay, I'll give that a shot.

Now is my logic off or does it seem that in any case the main breaker must be going bad (or something else with the supply)? I mean if it were *just* that the fridge were surging, wouldn't it blow it's own 15 or 20 amp breaker before the main, considering the only other appliances running are the 12,000 and 6,000 BTU ACs? Even if it's that everything is loaded on one bus, wouldn't those two ACs have to be pulling 30-35 amps for the main to blow before a 15-20 amp breaker? And isn't 30-35 amps way unlikely for those two units?

Or is my logic wrong?
 
  #14  
Old 06-28-05, 12:00 PM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Re-read my first post on this thread. _Heat_ will make a breaker trip. A bad connection will generate heat. If things go bad in the right (wrong) way, then a 15A load could trip your main breaker. If this is what is happening, then it will only get worse.

-Jon
 
  #15  
Old 06-28-05, 12:21 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Originally Posted by winnie
Re-read my first post on this thread. _Heat_ will make a breaker trip. A bad connection will generate heat. If things go bad in the right (wrong) way, then a 15A load could trip your main breaker. If this is what is happening, then it will only get worse.

-Jon
I get ya. I'll bring in a pro to check it out. Thanks again.
 
  #16  
Old 06-29-05, 12:35 PM
Member
Thread Starter
Join Date: Jun 2005
Posts: 35
Just for closure...

Yesterday the electrician found lose wires at the main, and at a few other breakers in the box. Tightened them up and things improved a little, but the main was still getting warm and eventually tripped. Came back today with a new fresh main, saw signs of arcing at the bus on the old one. Now things are better than they've been since I've lived here, which is 7 years.

Funny thing is a new breaker box was installed back then as a condition of the purchase, and it's never worked as well as now. So either the installer never tightened things down properly when installing, or he gave me a beat (used?) main to begin with.

Thanks for all the wise advise.
 
  #17  
Old 06-29-05, 12:50 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
That's one of the reasons I dislike requesting improvements by the seller as a condition of sale. The seller is motivated to do the cheapest job he can. Better to request a cash concession and let the buyer take care of it after the close.
 
  #18  
Old 06-29-05, 01:15 PM
Member
Join Date: Jan 2005
Location: United States
Posts: 455
Loose Connections

Amazing how many times you find that electrical problems can be fixed just by tightening a screw.

Outlets, Switches, Breakers, Ground and Common Buss Bars are all potential problems and they may be tight initially and get loose over time.

I had a sprinkler valve that wasn't working and when I opened the timer this morning I found that somehow the connection for that particular zone had come loose. I was really relieved when I tightened up and the zone then worked. I had no desire to dig up and replace 70' of direct bury wire.

More than once I've found that a loose screw someplace (often at the circuit breaker) was the problem with a non-functioning light or outlet. Most of the time it seems to be with tract homes - probably because the contractors and workmen are paid by the piece and rush the job.
 
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
'