50amp breaker hot, then it tripped

[TravelTiger]

Ok collective minds of the HOF,

I've already hit up some folks for advice on this, but I know we have some electricians on the forum that could also weigh in.

We're fulltiming in our 2016 4010RD (purchased Jan of 2016) and been at our park for 6 months. Park service has been consistent and no issues. Temps here have been around 100*, so of course both ACs run all day. Yesterday, about 4:30pm I caught a slight whiff of burning plastic smell. I opened the breaker panel door, and everything was kinda warm in there, but I'd never checked before so I didn't know if that was normal or not. I couldn't pinpoint any issue, and the smell wasn't directly coming from there -- it also seemed to dissipate and then I couldn't smell it.

Today, about 1:45pm, caught the same whiff of burning plastic, but it was stronger. Bent down to check the breaker panel and the exterior of it was warm. Touched the main double 50amp breaker and it was very hot. And the smell was coming from there. I went to unload the basement to start investigating, and that 50amp breaker tripped. Entered the coach and the burned smell was stronger. I killed all power at the pedestal and called my husband, who came home and took the panel cover off the breaker box. He removed the double 50amp breaker, and it was heat damaged (see pics below) The wires looked perfect, no burning at all. He checked all the wires to the breakers for tightness, and the wires to the neutral bus bar.

We removed and checked the 50amp cord connection at the back of the rig, it looked good. We don't have a transfer switch.

We have a portable EMS, which had no errors. Amp draw with all our usual things on, typically 24 on one leg, 22 on the other. Voltage runs about 118-122. Yesterday, I did notice it was a little lower in the afternoon, 113-116.

He replaced the breaker with a new one, and made sure the wires were tight. Reinstalled, all working fine, but still notice all the breakers are still warm to the touch this evening. Especially the two AC breakers (they are on separate legs, we checked). With a thermal gun aimed at the plastic breaker at about 5pm, they were about 114*. The breaker with the W/D which was not in use, at the bottom of the panel, was about 90*. Main breaker was 104*. Now, at 11:45pm, everything is cool to the touch (no ACs running, now.)

Would warm breakers imply something is still not right? What else do we need to investigate?


This is the old breaker, putting my nose to it, it smells burnt.

 

[Bones]

I found this little blurb. Maybe this will help.

http://www.schneider-electric.us/en/faqs/FA173839/

 

[hoefler]

Ok collective minds of the HOF,

I've already hit up some folks for advice on this, but I know we have some electricians on the forum that could also weigh in.

We're fulltiming in our 2016 4010RD (purchased Jan of 2016) and been at our park for 6 months. Park service has been consistent and no issues. Temps here have been around 100*, so of course both ACs run all day. Yesterday, about 4:30pm I caught a slight whiff of burning plastic smell. I opened the breaker panel door, and everything was kinda warm in there, but I'd never checked before so I didn't know if that was normal or not. I couldn't pinpoint any issue, and the smell wasn't directly coming from there -- it also seemed to dissipate and then I couldn't smell it.

Today, about 1:45pm, caught the same whiff of burning plastic, but it was stronger. Bent down to check the breaker panel and the exterior of it was warm. Touched the main double 50amp breaker and it was very hot. And the smell was coming from there. I went to unload the basement to start investigating, and that 50amp breaker tripped. Entered the coach and the burned smell was stronger. I killed all power at the pedestal and called my husband, who came home and took the panel cover off the breaker box. He removed the double 50amp breaker, and it was heat damaged (see pics below) The wires looked perfect, no burning at all. He checked all the wires to the breakers for tightness, and the wires to the neutral bus bar.

We removed and checked the 50amp cord connection at the back of the rig, it looked good. We don't have a transfer switch.

We have a portable EMS, which had no errors. Amp draw with all our usual things on, typically 24 on one leg, 22 on the other. Voltage runs about 118-122. Yesterday, I did notice it was a little lower in the afternoon, 113-116.

He replaced the breaker with a new one, and made sure the wires were tight. Reinstalled, all working fine, but still notice all the breakers are still warm to the touch this evening. Especially the two AC breakers (they are on separate legs, we checked). With a thermal gun aimed at the plastic breaker at about 5pm, they were about 114*. The breaker with the W/D which was not in use, at the bottom of the panel, was about 90*. Main breaker was 104*. Now, at 11:45pm, everything is cool to the touch (no ACs running, now.)

Would warm breakers imply something is still not right? What else do we need to investigate?

View attachment 46934 View attachment 46935 View attachment 46936
This is the old breaker, putting my nose to it, it smells burnt.

In picture #3, the breaker on the left had poor contact with the lug in the panel, picture # 2 showes a hot spot in this area as well. Loose connections generate heat causing even more heat to trip the breaker. Breakers will get warm/hot during high loads. Breakers trip by heat, this is the way they function. High draws, creates more heat, keeping the breakers cool during high loads helps keep them from tripping.

 

[wdk450]

Did the buss bar show heat degradation marks where the breaker made contact with it? If so, was that cleaned up to bright, shiny copper with some sort of abrasive scrubber (NOT STEEL WOOL)? This sounds like a good place to use some of the Cramolyn DeOxIt electrical contact cleaner/restorer spray I advocate. This stuff is available in small (expensive) sizes at Radio Shack, or in regular sizes from Amazon.com.
I don't know why de-energized breaker was getting hot - I would wonder if perhaps it was mis-marked and supplying current to something else. Best check would be a clamp-on ammeter on the load wire coming out of an individual breaker.
When in doubt, and dealing with a potential fire danger, I would change out any breaker I was concerned with. They cost a lot less than the hassle of an electrical outage, or the danger of a fire.

 

[TravelTiger]

Did the buss bar show heat degradation marks where the breaker made contact with it? If so, was that cleaned up to bright, shiny copper with some sort of abrasive scrubber (NOT STEEL WOOL)? This sounds like a good place to use some of the Cramolyn DeOxIt electrical contact cleaner/restorer spray I advocate. This stuff is available in small (expensive) sizes at Radio Shack, or in regular sizes from Amazon.com.
I don't know why de-energized breaker was getting hot - I would wonder if perhaps it was mis-marked and supplying current to something else. Best check would be a clamp-on ammeter on the load wire coming out of an individual breaker.
When in doubt, and dealing with a potential fire danger, I would change out any breaker I was concerned with. They cost a lot less than the hassle of an electrical outage, or the danger of a fire.

Bill, regarding your comment about a de-energized breaker, I'm not sure what you are referring to.


As far as the comment, "buss bar show heat degradation marks where the breaker made contact with it?" I am again not sure what you are referring to. The old breaker came out and the new one was very difficult to snap into place, so I know it was making a good connection. There was not any obvious damage that we could see behind where the breaker goes in.

Are you suggesting replacing the 2 Air Conditioner breakers that are getting warm , as well?

 

[Mattman]

I see either breaker loose or bad breaker. Those breakers are cheap cheap cheap. Not surprised one failed. Especially if your full timing. Check your connections at your AC units with your thermal gun as well. I have seen a 400amp main go on a building from a bad AC unit. It was fuaed at 30 Amps. High resistant faults can cause havoc. Trying shutting down an AC unit or other loads to see if the temperature drops. And check your shore power breaker. Maybe it melted closed.
Amp readings at your breakers are a good idea as well. Breakers are meant to run at 80% of there rating for a continuous load. Which is 3 hours or more. Your ACs running non stop all day could be running your breakers out side of its intended use.

 

[TravelTiger]

I see either breaker loose or bad breaker. Those breakers are cheap cheap cheap. Not surprised one failed. Especially if your full timing. Check your connections at your AC units with your thermal gun as well. I have seen a 400amp main go on a building from a bad AC unit. It was fuaed at 30 Amps. High resistant faults can cause havoc. Trying shutting down an AC unit or other loads to see if the temperature drops. And check your shore power breaker. Maybe it melted closed.
Amp readings at your breakers are a good idea as well. Breakers are meant to run at 80% of there rating for a continuous load. Which is 3 hours or more. Your ACs running non stop all day could be running your breakers out side of its intended use.

Thanks Mattman,

The breakers all got cooler at night, once the ACs stopped running constantly. This AM, the LR Ac is running already (9:30am) and that breaker is a tiny bit warmer than the others. They are Siemens Brand.

If there was an issue with the shore power breaker, won't my plug-in EMS catch that?

 

[Mattman]

I forgot you shut it off to change the breaker. The surge protector should catch the shore power. But I would just check there breaker with your thermal gun. Piece of mind.

 

[wdk450]

I was referring to the W/D breaker at 90 degrees. I guess this was meant to be a cool/no load breaker comparison. I thought that 90 degrees was too hot, but this depends on ambient temperatures, and heat radiated by hot breakers nearby.

Here are a couple of drawings on the buss the breakers plug in to, and possible burnt contact area problems. There are a couple of breaker buss styles - one the alternating L1 and L2 connection illustrated, and 2 solid connection bars at different heights which breakers with one of 2 different connection slots connect to. I don't know which style we have in our trailers.

Poor connections (whether in internal breaker/switch electrical contacts, or in electrical wiring contacts) cause heat when electrical current is passed through them. Heat on metal contacts causes metal corrosion, which causes even higher electrical contact resistance. This is a circular syndrome that usually results in electrical contact (and electrical circuit) failures.

Of course, your problems could be entirely within the mains circuit breakers (bad internal contacts), as a previous poster indicated. I always try to buy a name brand like Square D or Eaton circuit breakers. Everything has to have UL certification, but ongoing manufacturer quality is a big question.

Your 3rd breaker photo shows heat discoloration on one of the breakers where the breaker plugs into the buss. You will usually see corresponding heat discoloration on the buss contact point. This should be cleaned up or the box itself might have to be replaced.

 

[Nabo]

Erika - please let us know how your problem is doing. We are sitting in central AL with temps running in the upper 90's and indexes around 107 so I'm very interested in your situation. The other day I thought I smelled something but upon checking the surge protector, the coach is still only pulling <35 amps running both a/cs. I'm careful not to do any washing/drying or too many lights/microwaving until after dark when the a/cs start to cycle again. And this is the beginning of August - 3 more weeks of heat.

 

[TravelTiger]

Erika - please let us know how your problem is doing. We are sitting in central AL with temps running in the upper 90's and indexes around 107 so I'm very interested in your situation. The other day I thought I smelled something but upon checking the surge protector, the coach is still only pulling <35 amps running both a/cs. I'm careful not to do any washing/drying or too many lights/microwaving until after dark when the a/cs start to cycle again. And this is the beginning of August - 3 more weeks of heat.

Do me a favor and feel your breakers. Do they wiggle? Do they feel warm? Hot? Stick your nose down by them and smell.


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[Nabo]

Erika - it's raining now and has cooled down to 89 degrees, heat index 100.
1. all breakers are tight
2. the 2 a/cs breakers are warm but not hot to the touch
3. the 50 amp as well as the other breakers are cool to the touch.

 

[TravelTiger]

Ok Nabo, thanks. When it's hot hot hot again, check again for me.

My thoughts are we aren't finished solving our issue, but I had to be away from the rig for 1/2 a day today so I just cut the upstairs air off, moved fans to other circuits, turned off the water heater and disconnected any "nonessential" plugged in items around the rig.

Will be able to dig in more tomorrow and the weekend.



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[rxbristol]

Erika,

Out of curiosity, I shot the temps on my CB's. One leg of the 50 amp read 113 degrees while the other was 108. The 200 amp breaker was at 108 and the CB cabinet was at 102. Outside temperature was 98.

 

[TravelTiger]

Erika,

Out of curiosity, I shot the temps on my CB's. One leg of the 50 amp read 113 degrees while the other was 108. The 200 amp breaker was at 108 and the CB cabinet was at 102. Outside temperature was 98.

Thanks Rex, that seems comparable to what I was reading after the replacement breaker was in yesterday, and had been running about 3 hours.


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[TravelTiger]

Just a follow up to this thread, we ended up replacing both the AC breakers as well, as they seemed loose in the panel. With new breakers in place, the AC breakers still get warm, and so does the main breaker, but not as warm as the AC breakers running 8 hours a day. Overall, I've tied to cut back on electric usage in general, unplugging unnecessary draws around the rig and trying not to do laundry during the heat of the day.


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