# Main breaker keeps melting...



## Meadow (Jan 14, 2011)

What material Is the service entrance conducter copper or aluminum? What guage is it? 

Is there moisture in the basement? How far did you tighten the lugs and did you use noloax?

Take a pic of the burnt main if you can.


It could be the service conducters are to small, water leakage into the panel or improper tightening of the main lugs.


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## 220/221 (Sep 25, 2007)

Simply follow the path. There is resistance somewhere.

I once found a 3/0 service conductor burned up inside the rigid mast.

Why? Who knows?

You will also need to access the meter socket and look at the POCO crimps.


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## Meadow (Jan 14, 2011)

One more thing, If you have an IR camera, that will be your best friend.

Load up the service and see what gets hot.


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## kbsparky (Sep 20, 2007)

What are the load calculations and actual loads?

You may need an upgrade here ...


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## bobelectric (Feb 24, 2007)

Change the whole service,complete. Inspected, hooked up by power company.


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## MDShunk (Jan 7, 2007)

This isn't rocket surgery. Burnt up main.... hmm... high resistance connection directly on the load side, directly on the line side, or inside the breaker. It's one of those three choices. 

You got a leaky mast/SE cable that's directing water right inside this breaker?


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## brian john (Mar 11, 2007)

Amp Clamp, Fall of Potential test, proper PPE and case solved.


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## Shockdoc (Mar 4, 2010)

How do you know the bus bars were OK after all the heat of the original MB failing ? I'll bet the heat left damage to the bus bars. Panel replacement time.


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## Cletis (Aug 20, 2010)

*Fop*

here


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## mikeyrob (Mar 16, 2012)

Shockdoc said:


> How do you know the bus bars were OK after all the heat of the original MB failing ? I'll bet the heat left damage to the bus bars. Panel replacement time.


I did replace the bus bars the second time, I replaced all the guts.

1. There is no way water is getting in through the SE cable
2. I checked every connection and see absolutely no signs of resistance except on the neutral in the meter gang.
3. I checked every connection in the panel, every connection in the meter can, and climbed up and checked the aerial splice. everything seems fine.
4. I really wish I had an infrared camera.
5. it is #2AL SE cable, no damage to it, connections were tight in the panel, I always use NOALOX, 
6. I am eating this cost, I dont want to do a complete service change out if I'm not positive whats causing it.
7. Could it be from the POCO poles? the lines look fine but the transformer looks 100 years old.


* Please don't get started about the endless debate. Where I come from EVERYONE uses Aluminum SE cable for residential. And I mean everyone.


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## mikeyrob (Mar 16, 2012)

MDShunk said:


> This isn't rocket surgery. Burnt up main.... hmm... high resistance connection directly on the load side, directly on the line side, or inside the breaker. It's one of those three choices.
> 
> You got a leaky mast/SE cable that's directing water right inside this breaker?


Thats what I would say. I have ran into the scenario many times, everything seems a little different with this house though. Its really got my brain going.


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## Shockdoc (Mar 4, 2010)

mikeyrob said:


> I did replace the bus bars the second time, I replaced all the guts.
> 
> 1. There is no way water is getting in through the SE cable
> 2. I checked every connection and see absolutely no signs of resistance except on the neutral in the meter gang.
> ...


Murray panel? AL bus bars ? 
* I'm a AL service guy myself.


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## mikeyrob (Mar 16, 2012)

Shockdoc said:


> Murray panel? AL bus bars ?
> * I'm a AL service guy myself.


I forget what the original panel was, but I replaced it with Eaton guts. And it is AL bus bars.


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## MDShunk (Jan 7, 2007)

I did replace the bus bars the second time, I replaced all the guts.

1. There is no way water is getting in through the SE cableFamous last words
2. I checked every connection and see absolutely no signs of resistance except on the neutral in the meter gang.Resistance isn't something you see. It's something you measure.
3. I checked every connection in the panel, every connection in the meter can, and climbed up and checked the aerial splice. everything seems fine.Quit looking at all that other stuff, and look directly on both sides of the breaker or inside the breaker.
4. I really wish I had an infrared camera.You've squandered what you've done so far, so the IR camera will do you no good.
5. it is #2AL SE cable, no damage to it, connections were tight in the panel, I always use NOALOX, Sometimes you can see cable damage, sometimes you measure it.
6. I am eating this cost, I dont want to do a complete service change out if I'm not positive whats causing it.Then do a damn FOP test and quit wasting you own money.
7. Could it be from the POCO poles? the lines look fine but the transformer looks 100 years old.Nope.


* Please don't get started about the endless debate. Where I come from EVERYONE uses Aluminum SE cable for residential. And I mean everyone.[/QUOTE]


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## brian john (Mar 11, 2007)

mikeyrob said:


> I did replace the bus bars the second time, I replaced all the guts.
> 
> 
> 4. I really wish I had an infrared camera.


You have all the IR devices you need if you have DMM (DIGITAL MULTI-METER)

Perform a fall of potential test across the device in question.


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## mikeyrob (Mar 16, 2012)

Thank you for the posts that were real advise, it means a lot. And thanks for the condescending ones too!


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## Meadow (Jan 14, 2011)

What loads are there in the residence? There electric heat or a hot tub by chance? 

Is it one leg all the time or both or does it rotate?



The others are right, your best bet is an IR under full load. My belief is the problem is under your nose but its hard to spot.


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## niteshift (Nov 21, 2007)

To rule out poco's end, maybe your utilty will come to the residence, do the load test at the meter, may find it is at the load side or, it could be at thier connections at the pole. BGE does this. I had a similar problem and had them come out, they found it was thier connection at the pole.


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## 220/221 (Sep 25, 2007)

If I were you, I'd ask BJ some follow up questions.


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## 360max (Jun 10, 2011)

FOP Test

http://www.fluke.com/fluke/usen/solutions/earthground/fall-of-potential.htm


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## mikeyrob (Mar 16, 2012)

Hey guys thanks for all the help. I just got back from my friends house. I knew I was making a much bigger deal of this then it was. Like I said when I fixed it the first time I literally checked every possibility. I got there today and it was just a bad breaker for a lighting circuit. When I replaced the guts and main last time I only replaced about half the breakers because thats all that I had with me at the time. Knew I shouldn't have second guessed myself. thanks everyone.


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## SignGuy1980 (May 19, 2012)

So a bad lighting circuit was causing the main breaker to melt?
I'm confused...


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## mikeyrob (Mar 16, 2012)

SignGuy1980 said:


> So a bad lighting circuit was causing the main breaker to melt?
> I'm confused...


haha sorry. There was no melted main breaker this time, just a simple bad breaker. I just thought it was the main again.


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## erics37 (May 7, 2009)

360max said:


> FOP Test
> 
> http://www.fluke.com/fluke/usen/solutions/earthground/fall-of-potential.htm


That's a test for electrode resistance to earth. Here's the FOP test that BJ is referring to (quoted from a past thread):



> While replacement will happen a good tech should know why he is replacing a device.
> 
> 
> 
> For example with a 3-phase Circuit Breaker that is nuisance tripping, measure current (balance loads are beneficial but not necessary), then measure from the line bus to the load conductors (if bare conductor is exposed), for all three phases. If one phase has a higher that average millivolts reading, then try to isolate this issue. Measure from line bus to the Circuit Breaker bus stab, if all 3-phases have millivolts readings that are the same (or close to the same) measure from the bus stab to the load side conductor termination connector (through the Circuit Breaker), if all these readings are close, next take measurements from the load side termination connector to the load conductor. In this case you can determine if it is a line bus connection issue, bad Circuit Breaker or a load conductor termination issue. Any accessible portion of the device can be tested in this method.


Eric I missed this thanks.


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## swimmer (Mar 19, 2011)

mikeyrob said:


> 4. I really wish I had an infrared camera.


If cost is a problem, then try a no-contact infrared thermometer. Should be less than $40. You should be able to get one at Home Depot or Radio Shack.

Mine came in pretty handy the few times I've used it.


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## greenman (Apr 20, 2012)

I had the same thing happen to one of my rental houses. It was the Main breaker.
Swap her out, I have not had an issue since.


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## nolabama (Oct 3, 2007)

mikeyrob said:


> haha sorry. There was no melted main breaker this time, just a simple bad breaker. I just thought it was the main again.


Lights were flickering and it got you worried. Our POCO has an IR camera they will show homeowners the guts of their panel all hot and about to burn up. They do this if the homeowner calls and says they have a problem with their lights flickering. And they pull your meter and make you get electrician. Lol.


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## brian john (Mar 11, 2007)

360max said:


> FOP Test
> 
> http://www.fluke.com/fluke/usen/solutions/earthground/fall-of-potential.htm


That is a 3 point fall of potential ground testing.

I'll post what I wrote regarding FOP and DMMs and acronym's on Monday.


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## CFL (Jan 28, 2009)

mikeyrob said:


> Thank you for the posts that were real advise, it means a lot. And thanks for the condescending ones too!


That is a case of the truth hurting. Take all of those "condescending" remarks and store them in your memory, as they are the best pieces of advice you got from this. If you don't understand what Brian John and MDShunk were talking about, make sure you do. That might be the most useful troubleshooting method out there.


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## Cletis (Aug 20, 2010)

*this*



CFL said:


> That is a case of the truth hurting. Take all of those "condescending" remarks and store them in your memory, as they are the best pieces of advice you got from this. If you don't understand what Brian John and MDShunk were talking about, make sure you do. That might be the most useful troubleshooting method out there.


Watch this and learn. I did. You will do well on this site if you master this

http://www.youtube.com/watch?v=U2StPWy7GkA


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## Roger123 (Sep 23, 2007)

Cletis said:


> Watch this and learn. I did. You will do well on this site if you master this
> 
> http://www.youtube.com/watch?v=U2StPWy7GkA


That is soooo right!!!!


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## brian john (Mar 11, 2007)

*An old post*

We are often called by electrical contractors to investigate why fuses are blowing or CBs are tripping. Many times the cause is a high resistance connections resulting in sufficient heat to effect the thermal element in the fuse or CB.

A simple method to isolate the high resistance connection and thus the source of the heat is the Fall of Potential Test Method, commonly referenced to as the FOP test. To perform this test, one simply needs a multimeter with a millivolt scale, and an amp clamp.

There needs to be a load on the device to be tested, preferably a balanced load or close to balanced load. In the case of a fused safety switch (FSS). One would measure current across all three phases, then measure from line to load of one pole/phase of the conductor strands (if exposed) for each pole of the FSS. If one phase has a higher that average millivolt measurement (actually the voltage drop across the device under test). Your next measurement would be from line conductor to line of the fuse, if all readings are close to equal move to the next components of the FSS, in this manner you an isolate the high resistance connection.

With an arranged outage repairs can be implemented and a repair FOP measurement taken to verify repairs.

Our thermographers perform this test as part of their IR Scan to isolate to high resistance issue. As sometimes it is not possible to determine from a picture if the issue is a CB connection to the bus or the CB. Additionally it is not feasible to use a DLRO (Digital Low Resistance Ohm Meter)/ Micro ohm-meter to take measurements on small CBs and FSS due to contact point spacing of the test instruments, so our technicians take pre-repair and post-repair measurement s to verify repairs.


An example we IR’d a 200 amp CB this weekend with 155 amps per phase (average), millivolt readings were 38mv, 91mv and 42 mv. The readings were taken from the bus stabs of the CB, negating any possible issue with the CB to bus connection or conductor termination connector to CB connection. B phase had an issue, when we replace the CB we will do further testing and open the CB to see if visual thermal damage has started.

This test can be performed on single pole CB, or any 3-pole devices, we have used this on 4000 amp bolted pressure switches.

As with any testing of exposed energized parts, all safety cautions must be observed, wearing of PPE, isolating the area to be worked in. One issue we have had over the years is customers taking FLASH photography as we are taking measurements. We no longer permit customers to take photos, without prior notice. This minimizes heart attacks.


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## bobelectric (Feb 24, 2007)

Thanks,Brian. You earn your keep sometimes.


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