Need help diagnosing a panel issue.

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Might be worth taking those off and the neutral, wire brushing it all, some noalox and put it all back together.
 
Load things up and see what starts heating up.

As mentioned right main lug looks discolored, possibly has been overheated.

What little bus you can see between main and branch breakers, they are not same color there so one may have been overheated. If so I'd suggest replacing everything, anything that has been subjected to overheating will just come back and bite you later.
Coppersmith said:
I'm unfamiliar with this test. Can you elaborate?
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place volt meter leads across line and load of breaker and test for voltage drop through the breaker.
 
kwired said:
Load things up and see what starts heating up.

As mentioned right main lug looks discolored, possibly has been overheated.

What little bus you can see between main and branch breakers, they are not same color there so one may have been overheated. If so I'd suggest replacing everything, anything that has been subjected to overheating will just come back and bite you later.

place volt meter leads across line and load of breaker and test for voltage drop through the breaker.
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Also check the voltage at the load.
 
kwired said:
place volt meter leads across line and load of breaker and test for voltage drop through the breaker.
Click to expand...

Could also measure the voltage between the exposed part of the service conductor and the main breaker terminal that it goes to. That would show the voltage drop across the connection itself. This would done under load and with a clampmeter on the service conductor to measure the current going through the connection.
 
Coppersmith said:
View attachment 2563421

A few days ago I did a service call here. There is a smoky smell in this panel. Nothing (including the main) feels warm. I removed all the branch breakers and inspected the breakers and the bus. The only damage I could find was under a two-pole twin (4th and 5th breaker on left side) where a plastic fin on the bus was melted. That 20 amp breaker is connected to a 18.75 amp water heater. I replaced the breaker and relocated it to a spot with more air circulation.

The panel is in a closet. I closed the door and turned off the light. It was pitch black in there. I could see no arcing or flame. I found no terminations that were loose.

Last night the client was watching TV in bed so I suspect there was a light total load. The 150 amp main breaker tripped. I'm at a loss as to what could be causing the issue. I'm thinking there is a main breaker failure of some sort, but like I said the breaker was cool to touch when I last checked.

I'm heading over there soon. I'm hesitant to change the main without knowing the cause. Please give me suggestions, Thanks.
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Does anyone else notice that the top RH terminal of the main looks overheated and discolored ?
 
Also curious as to what all this panel feeds. Why are there two 40A double poles? One would be the range. Is there an AC unit? Hopefully its not going to a 30A dryer receptacle. Also, that double pole with the large wires -- is that going to a sub panel? You could have some problem downstream that kicks the main before the sub breaker, or it could be a bad connection on the main as others have indicated.
 
UPDATE:

So I went over there and checked the feeder lugs and the bus bar connections. Everything was tight. However I discovered that the top right lug was loose to it's connection INSIDE THE CASE. In other words, this is a manufacturing defect. When peering inside the lug after the conductor was removed, I could see some burnt material. So I ordered a replacement main breaker and will be installing in Saturday. (I offered Friday, but the client has a doctor's appointment that can't be missed.) I left the right feeder disconnected and safed it off. Then I turned on the main so the client would have partial power until I can make the replacement. Luckily it's not super hot in Florida this time of year so lack of A/C is not a problem, but cold showers would be a problem for me. I rearranged some of her breakers maximize power to critical outlets like the fridge.
 
Coppersmith said:
I agree it's too high, but the cable is 12ga so I can't put a larger breaker in. This is a manufactured home so cable is inaccessible. Client has limited funds, so I can't run a 10ga cable. I don't think this is the source of the main trip problem.
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Manufactured home…aka trailer, client has limited funds….in other words broke. May be time to walk away.
 
ptonsparky said:
I've had the wealthiest of clients not pay a $20 service call made on a Sunday,. IIRC. (Not that it should matter, I outlived him.).I've also had those with limited funds pay every penny, even if it took some time to do so.
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I can say about the same thing.

Many years ago I did some work for a older woman, she started to make monthly payments and did pay them every month.

When I found out she would be moving out of the area I figured I'd never see the rest of what she owed, but she continued to pay each month until it was all paid.

Then I've had one or two that most likely could afford to pay a rather modest service call that pretty much refused to pay it.
 
Coppersmith said:
UPDATE:

So I went over there and checked the feeder lugs and the bus bar connections. Everything was tight. However I discovered that the top right lug was loose to it's connection INSIDE THE CASE. In other words, this is a manufacturing defect. When peering inside the lug after the conductor was removed, I could see some burnt material. So I ordered a replacement main breaker and will be installing in Saturday. (I offered Friday, but the client has a doctor's appointment that can't be missed.) I left the right feeder disconnected and safed it off. Then I turned on the main so the client would have partial power until I can make the replacement. Luckily it's not super hot in Florida this time of year so lack of A/C is not a problem, but cold showers would be a problem for me. I rearranged some of her breakers maximize power to critical outlets like the fridge.
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I've replaced a few of that exact model breaker. I don't think the brand necessarily is the problem, but they were all GE. I don't think it would hurt to leave it connected until Saturday. About all will happen is it might trip. Just make sure connections are tight and maybe keep the loads to a minimum. I wouldn't want to go without hot water for 3 or 4 days. You couldn't even heat it on the stove with one leg disconnected.
 
Little Bill said:
I don't think it would hurt to leave it connected until Saturday. About all will happen is it might trip. Just make sure connections are tight and maybe keep the loads to a minimum. I wouldn't want to go without hot water for 3 or 4 days. You couldn't even heat it on the stove with one leg disconnected.
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I think you'd be able to get some hot water by connecting the phase of the water heater that was disconnected to neutral. The power delivered would go down to 1/4 of what it was before by running it off of120V instead. But it's possible it could even reach the same temperature as before, just with a much longer recovery time.
This is assuming that the water heater doesn't have electronic controls, and it's not a tankless one.
 
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