Main Breaker Question


  #1  
Old 07-11-05, 05:57 AM
DaGbyte
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Main Breaker Question

It's been popping for no real reason. The left side of the breaker is hot to the touch, so I called out an electrician. He did some snooping and pooping and checked to see the load across the 2 phases was balanced. One phase was pulling 60 amps, the other 30 with the vacuum, AC, all the lights, exhaust fans, clothes dryer and a hair dryer running. My real concern is the fact the breaker is HOT to the touch. If it's going south, what can I expect to pay for a new one? It's a Seimen's 150 amp breaker.
 
  #2  
Old 07-11-05, 06:31 AM
W
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Take a look at this thread:
http://forum.doityourself.com/showthread.php?t=220015

If the electrician measured the currents at below 60A on a 150A breaker, and the breaker was _hot_, then you have one of three problems: a loose wire to the breaker, a loose connection between the breaker and the main bus, or a bad main breaker. The electrician should have checked all of these.

Good luck!

-Jon
 
  #3  
Old 07-11-05, 06:39 AM
DaGbyte
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He did... He yanked off the meter, opened the box, jiggled and wiggled all he could. He said it's not very common for main breakers to go bad, but it could be the culprit if it's hot.

I read the thread when I had posted my last questions. Since the load, with everyhting running, is only drawing 60 amps, I can't imagine that could be trippping the breaker.
 
  #4  
Old 07-11-05, 07:48 AM
J
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In addition to the three reasons Jon mentioned, ambient heat could also be contributing. If your breaker box is located on the south or west side of a house in Phoenix in the summer, the sun could be baking it.
 
  #5  
Old 07-11-05, 08:55 AM
DaGbyte
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Actually John, it's northern NJ, but it does face the sun for most of the morning. Yesterday when it popped, it was around 11:30, sunny, and about 85F. Pretty sure that wouldn't do it... or could it? But the breaker get's r-e-a-l-l-y hot, and I'm sure that's not good.....
 
  #6  
Old 07-11-05, 09:22 AM
W
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Breakers trip for two reasons: extreme high current causing the 'magnetic trip' element to trigger, or _heat_.

In a properly working breaker, current causes a small element inside the breaker to heat up. 'Overcurrent' will cause this element to get too hot, and make the breaker trip. High ambient temperature means that less current is required to make this element get too hot, so if the breaker is warmed up from the outside, less current is required to make it trip. Make a breaker hot enough, and it will trip with no current flowing at all.

In a properly working breaker, current near the trip level should make the breaker noticeably warm, but _not_ extremely hot.

I am quite confident that you have a loose connection either right next to the breaker or a bad contact inside the breaker. This loose connection is getting _very_ hot at moderate current, and this heat is causing the breaker to trip.

If you are lucky, this loose connection is simply where the wire connects to the breaker, in which case tightening up the connection is all that is needed. If you are unlucky, then the bad connection is inside the breaker, and you will need to replace it. If you are extremely unlucky, then the bad connection is between the breaker and the main bus, and the heating will have damaged the bus. In this latter case, you will probably have to replace your breaker panel.

The electrician should have been able to determine which of these was the problem. If they actually had the meter pulled and the power off, then they should have checked the wire and the bus connection, and determined if they were the problem or not.

-Jon
 
  #7  
Old 07-11-05, 09:29 AM
J
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So does it ever trip in the evening?
 
  #8  
Old 07-11-05, 06:16 PM
DaGbyte
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The whole tripping thing has only happened recently - I'm guessing that rules out ambient temperature. And the fact I hate the heat and run the AC alot - and the dryer - i'm guessing it really is a bad main breaker.

I had them replace it today, so I guess we'll find out!

The electrician was pretty thorough. It was kind of funny - he would grab the wires inside the main breaker box - even checked the screws on the main feeds with not a hesitation - but when he was playing with the prongs on the meter, he had a faint twitch of the screwdriver and an i've-been-bitten-before-so-I'll-show-this-beast-a-little-respect kind of attitude

checked the edges of the wires - no sign of arcing. Checked the contatcs on the main breaker and meter, no sign of arcign either. He did run an ammeter over the circuits while "every light in the house is on" and i learned that the heater in my baby's room draws 13... THIRTEEN amps on a 15 amp circuit. Given the shoddy work by the e.c. on this place, I'llbe looking at all the outlets and switch boxes to make sure they're screwed and pigtailed and not stripped and stuffed.

I'm just glad computers aren't this complicated!

Thanx for the supprt. nice to see a board that doens't give the newbs a hard time!

-DaG
 
 

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