Help! Furnace Breakers Melting!!!

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bubby

Member
Good morning all. I need your help. My company wired a 200+ unit apartment complex two years ago. Last month, we got a call from the on site maintenance tech called and asked us to provide him with (50) replacement 50-amp, two pole breakers for the electric furnaces. Of course, we asked why and he said that the furnace breakers were overheating and melting.

We IMMEDIATELY sent out a crew and began unit by unit inspections. In approximately (50) of the unit panels (125A MLO's with aluminum bussing), we found the furnace breakers in various states of meltdown and damage to the bussing where they snap in.

The wiring method and spec's were as follows:

Cutler Hammer BR series - 125 amp MLO's with aluminum bussing
Furnace overload protection: Cutler Hammer BR 2-pole 50A breaker
Conductors: #6 Aluminum SEU
Inhibitor: Ilsco De-Ox
Terminations at breakers we tight
Furnace loads: 9,700 VA
Voltage: 240
Phase: Single
Furnace field amp read at furnace startup, 41 amps.

The ranges were also wired with #6 SER aluminum with 50A, 2-pole BR breakers. There were no problems with these circuits.

Worth noting (as we are chasing our tails):
The furnaces were set after the electrical rough was completed. After the furnaces were set, we were able to read the decal on the furnace J-cover "terminate copper only." As the furnace had a pull out disconnect, inside the mechanical area of the furnace, we installed insulated dual rated AL/CU butt splices ahead of the furnace disconnect to transitioned from aluminum to copper (#8 THHN, rated at 50A, like the wire). There was no damage to these butt splices or terminations.

We contacted Cutler Hammer and they now have the damaged bussing and breakers at their laboratory. There is visible latex paint overspray on the bussing and the breakers (painters obviously pulled panel covers off when they were painting). They feel this is the most likely cause. I.e. Latex paint on the bussing doesn't allow the breakers to seat against the bussing 100% and this created arcing. Our customer feels this explaination is BS.

Also of note, in many cases, the wire melted off the furnace breaker in the panel. However, the breaker did not trip.

Does anyone have any experience with this sittuation or any idea what could be causing this sittuation?????

Could it be a furnace issue? A voltage drop issue at the utility primary causing amperage to increase? I.e.:

If the incomming voltage was too low (say 180V phase to phase) divided by 9,700 W furnace load = 54 amps
If the incomming voltage was OK (240V) divided by the furnace load of 9,700 = 40 amps - withing parameters

Thank you very much for your replies!!!!
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Well it certainly can be defective equipment or the paint but depending on a few things the install may not be legal. When was this install done? You are certainly pushing the max on the wire ampacity. And if you should be using the 60C rating, for se cable then the install would not be compliant.

I would bet the spray is the issue. The range doesn't see the problem because it rarely will see anything close to 50 amps and the ranges is not on for hours and hours as a furnace would be.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
When a number of items have a similar failure, then it is highly probable that they all had the same cause. Your choices of equipment seem appropriate. The only common factor appears to be the paint. I believe that is the cause, regardless of whether your customer thinks otherwise. My only reservation is that if the breakers were in place before the covers were removed and the painting took place, how would paint have gotten in the way of the contact between the breaker and the bus? My guess is that the paint seeped into that area while it was still liquid.

How then, your customer might ask, did the furnace breakers all fail, but the breakers serving the ranges not fail? My answer is that the furnace is more likely to be operated close to its full rated power for more hours at a time than the range. Your profile does not give your geographic area, but I would venture to guess that it is an area that uses a lot of heating during the winters. So perhaps many of the breakers in the panels had been hit with paint, and many of them experienced higher than normal temperatures, but only the furnace breakers failed because they were hot for longer time periods.
 

bubby

Member
Well it certainly can be defective equipment or the paint but depending on a few things the install may not be legal. When was this install done? You are certainly pushing the max on the wire ampacity. And if you should be using the 60C rating, for se cable then the install would not be compliant.

I would bet the spray is the issue. The range doesn't see the problem because it rarely will see anything close to 50 amps and the ranges is not on for hours and hours as a furnace would be.

Hi Dennis and thanks for your reply. The install was done two years ago (in a juridiction that hadn't adopted NEC 2008).

Thanks again Sir.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I have seen the overspray cause this problem many times. The overspray on the bus is a violation of 110.12(B).
As far as the wire melting off the breaker, that is normally a termination issue. Were the connections tightened to the manufacturer's torque spec? With this type of termination on aluminum conductors, too tight is just as bad as too loose.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
If the incomming voltage was too low (say 180V phase to phase) divided by 9,700 W furnace load = 54 amps
You are talking about a voltage of 75% of rated. If it were that low, then there would be many more problems. But your math is wrong. A furnace would not operate at constant power. Instead, it has a constant resistance. So if the voltage drops, the current will drop also.

 

bubby

Member
You are talking about a voltage of 75% of rated. If it were that low, then there would be many more problems. But your math is wrong. A furnace would not operate at constant power. Instead, it has a constant resistance. So if the voltage drops, the current will drop also.

Hi Charlie. You are correct in that my math is wrong. Thank you for your reply.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Our customer feels this explaination is BS.

Yes, because he is obviously an expert right?

I have to agree with the others. First off, because it's HIGHLY unlikely to be a load related issue. If it was, the breaker would have tripped! If the breaker didn't trip, that means the problem happened AHEAD of the sensing elements of the breaker, i.e. where the breaker attaches to the bus. If it happened there, there would be no reason for the breaker to trip, its sensing elements would not see the problem, until maybe the radiated heat makes it's way to the thermal device or the melted bus causes a short on the load side. So all the theories of low voltage, conductor sizing, termination issues are moot.

Secondly, we have no way of knowing how and what got in there as a result of the paint over spray. Water based latex paint out gasses ammonia when wet, that could have started a fairly severe corrosion reaction on the bus. If it was "oil" based pain, who knows how deeply the solvent would have penetrated and what it carried with it. Pigments contain all kinds of nasties such as cadmium, chromium, titanium etc., all with various chemical reaction properties to aluminum (and copper for that matter). Bad, bad, bad situation no matter what.

There is no excuse for the painters not performing their due diligence before spraying around electrical equipment. Assuming it was not hot at the time, all they would have had to do was put masking paper over it. They failed, they caused it in my pinion.
 

growler

Senior Member
Location
Atlanta,GA
Last month, we got a call from the on site maintenance tech called and asked us to provide him with (50) replacement 50-amp, two pole breakers for the electric furnaces.

There were Latex paint on the bussing doesn't allow the breakers to seat against the bussing 100% and this created arcing. Our customer feels this explaination is BS.

The reason the customer feels the explaination is BS is because the scope of the problem gets much bigger than they want to deal with.

The replacement of 50 ea. 50 amp two pole breakers is one thing ( and wouldn't do any good in the long run ) and having to check out and possibly replace all 200 panels with new guts and breakers is another. I'm assuming that the breakers were not installed at the time of the paint spraying.

If the painter sprayed the buss bars of all the panels then the only long term fix is to replace all the panel guts and install all new breakers. It's a huge problem and will get expensive.
 

rich000

Senior Member
I am assuming they are looking for someone to blame and pay for this issue.

In your case, you have the formal report from the manufacturer stating what caused the problem. The paint could cause the issue you are describing.

In my opinion, it is the electrician who installed the breakers onto a painted bus who is at fault here. If they saw the paint on the bus, they should have stopped and resolved the issue there (i.e. replace bus on painters dime).
 

bubby

Member
I am assuming they are looking for someone to blame and pay for this issue.

In your case, you have the formal report from the manufacturer stating what caused the problem. The paint could cause the issue you are describing.

In my opinion, it is the electrician who installed the breakers onto a painted bus who is at fault here. If they saw the paint on the bus, they should have stopped and resolved the issue there (i.e. replace bus on painters dime).

Hi RichOOO and thank you for your reply. If I read this thread as a poster and not the author, I would completely agree with you. However, our customer is truly a cut above and I think they are primarily looking for absolute safety for their tenants at this point. I'm sure the finger pointing will come but it is down the road at this point.

As for snapping in breakers on a bussing with over spray, all I can tell you is that in new construction, there often is drywall dust etc on the bottom of a load center while breakers are being snapped in. Most likely, the guys didn't think a thing about it, rather they thought either A. drywall dust or B. will rub off as breaker snaps on. I've been doing this for over twenty years and I had no idea that overspray could cause this problem. I'm sure my crews didn't either...They WILL no though!

Thanks for your response Sir!
 
I realize that better minds than I have already commented, but with that many failures, there's always the possibility of manufacturing defect. It would also make sense to look at some non-melted units for over-spray and maybe remove some in-service breakers for inspection & test.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I realize that better minds than I have already commented, but with that many failures, there's always the possibility of manufacturing defect. It would also make sense to look at some non-melted units for over-spray and maybe remove some in-service breakers for inspection & test.

I know I am going to catch some flak for this, but we call C-H breakers 'never trips'.

I have seen a 15 amp C-H breaker hold 115.7 amps for at least the two seconds it took me to shut off the breaker. The voltage drop was enough to almost kill the lights in the basement.

For some reason, C-H went from the Cadillac of equipment down to the Yugo.

I'll bet the issue is a result of slack QC on the part of C-H. I'll also bet they won't pony up to it and try to blame it on something else.

I would LOVE to see some pics of the melted C-H breakers. PLEEZE post them!
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Hi RichOOO and thank you for your reply. If I read this thread as a poster and not the author, I would completely agree with you. However, our customer is truly a cut above and I think they are primarily looking for absolute safety for their tenants at this point. I'm sure the finger pointing will come but it is down the road at this point.

As for snapping in breakers on a bussing with over spray, all I can tell you is that in new construction, there often is drywall dust etc on the bottom of a load center while breakers are being snapped in. Most likely, the guys didn't think a thing about it, rather they thought either A. drywall dust or B. will rub off as breaker snaps on. I've been doing this for over twenty years and I had no idea that overspray could cause this problem. I'm sure my crews didn't either...They WILL no though!

Thanks for your response Sir!

Kind of interesting that the 'over spray' only affected one particular model of breaker, and did so en-mass.
 

rt66electric

Senior Member
Location
Oklahoma
AL termination at the Breaker???

AL termination at the Breaker???

I often have " smashed" breakers to __(A)- Save the silver contacts ______-(B) see if anything failed internally??


Most of the breakers Above 30amp that I have torn apart have failed at either the stab clip or at the termination screw.

very seldom have the contacts show wear.

I would suspect the AL termination at the breaker overheating.

Try splicing a AL_Cu connector similar to the connection at the furnace??

Or checking the torque at all of AL connections.

Are CH-breakers rated for AL?? In some old 70's panel I have seen White plastic breakers especially for AL wire. THe termination screws were similar to AL-rated devices.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
I have seen a 15 amp C-H breaker hold 115.7 amps for at least the two seconds it took me to shut off the breaker. The voltage drop was enough to almost kill the lights in the basement.
...
How did you come up with the current measurement? 116 amps is a bit high for a 2 second trip, but the high end of the time current trip curve shows 90.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
I know I am going to catch some flak for this, but we call C-H breakers 'never trips'.

I have seen a 15 amp C-H breaker hold 115.7 amps for at least the two seconds it took me to shut off the breaker. The voltage drop was enough to almost kill the lights in the basement.

For some reason, C-H went from the Cadillac of equipment down to the Yugo.

I'll bet the issue is a result of slack QC on the part of C-H. I'll also bet they won't pony up to it and try to blame it on something else.

I would LOVE to see some pics of the melted C-H breakers. PLEEZE post them!

Are you sure it's the CH style? Not the BR style? BR's are warmed over Westinghouse breakers and are not very quick to trip. I have never had a CH style give trouble, very small arc on a short circuit, comparable to the Square D QO style.
 

big john

Senior Member
Location
Portland, ME
Kind of interesting that the 'over spray' only affected one particular model of breaker, and did so en-mass.
Agreed. Something doesn't add up.

If it really is the result of over-spray then the only common factor on all these breakers is the heavy load. If the over-spray is bad enough to cause that many failures, I would expect signs of overheating and the beginnings of failures on other breakers as well, especially heavily loaded ones like cooktops.

The OP mentioned that not all of the 200 breakers had this problem. What's the difference between the condition of the bus on the affected breakers and the unaffected ones? If we're talking about that much overspray, I would expect to see obvious differences on the failed buses versus the normal ones.

If it came down to it, I might seriously consider sending a few of the damaged breakers to be independently examined.

-John
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
We IMMEDIATELY sent out a crew and began unit by unit inspections. In approximately (50) of the unit panels (125A MLO's with aluminum bussing), we found the furnace breakers in various states of meltdown and damage to the bussing where they snap in.

We contacted Cutler Hammer and they now have the damaged bussing and breakers at their laboratory. There is visible latex paint overspray on the bussing and the breakers (painters obviously pulled panel covers off when they were painting). They feel this is the most likely cause. I.e. Latex paint on the bussing doesn't allow the breakers to seat against the bussing 100% and this created arcing. Our customer feels this explaination is BS.

Also of note, in many cases, the wire melted off the furnace breaker in the panel. However, the breaker did not trip.

Everyone seems to be focused on the overspray only. I only have one question. How can overspray on the buss(line side of the breaker) combined with melted wiring(load side of the breaker) with no breaker trips not be a manufacturing problem?

Overspray-Installer Error

Possibly mistorqued lugs-Installer Error

Heat from poor connections on both sides of the breaker WHILE still passing 40 amps through it without tripping-Manufacturing Defect???
 
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