Message Board Thread - "Electrical service"

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Electrical service darby 4/6/2010
Would greatly appreciate some opinions.This is a 240V residential service conductor and master circuit breaker. The load is unknown (a few lights, fridge and furnace running) The temperatures do not appear hot but there is a noticeable temperature gradient. Normally it looks more consistent along the length of the wire. Could this be a termination problem or faulty breaker? Also, does anyone have any suggestion as to how much greater the temperature of the conductor would be compared to the insulation?
Thanks
 
Re:Electrical service jvoitl 4/6/2010
Not enough info. What's the current and what's the breaker rated at? It looks like 100A breaker but not sure from the image.
 
Re:Electrical service Jkays 4/7/2010
If you are going to scan a residential panel you need to put it under a load with everything on otherwise you won't see any problems areas. Most people don't scan residential panels because of the liability. You also will need an amp reading. It does not appear there is anything wrong with it as it is work in this pic.
 
Re:Electrical service Jkays 4/7/2010
If you are going to scan a residential panel you need to put it under a load with everything on otherwise you won't see any problems areas. Most people don't scan residential panels because of the liability. You also will need an amp reading.
 
Re:Electrical service Jkays 4/7/2010
Jkays wrote:
are going to scan a residential panel you need to put it under a load with everything on otherwise you won't see any problems areas. Most people don't scan residential panels because of the liability. You also will need an amp reading. It does not appear there is anything wrong with it as it is work in this pic.
Sorry for my first posting. I am a first time poster here. Does any one know how to edit a posting if you hit the post button to fast?
 
Re:Electrical service jvoitl 4/8/2010
I just read your thread again and something dawned on me that I should have noticed the first time. You said this is a 240 volt breaker, but in reality it’s 2, 120 breakers ganged together for the two 120 legs of the single phase 240. The breakers have a thermal element in them so they are always a little warm if there is current flow. In this image it appears that the normal heat from the breaker is being conducted to the wire, but I would go ahead and check the termination just in case.
You also said that normally it looks more consistent along the length of the wire. The loads you mentioned, refrigerator, furnace etc. are all 120 volt loads. They conduct from one of these 2 ganged breakers to neutral. If the 120 volt loads are not split up exactly even between the two breakers, they never are, one breaker and wire will always be a little warmer.
 
Re:Electrical service brodie 5/5/2010
I would suspect the circuit breaker to have a high internal resistance on one phase.Take a comparitive millivolt drop test across each phase and compare.Circuit breakers should be exercised annually to prevent contact oxidation.
 
Re:Electrical service soccerchainsaw 5/5/2010
darby wrote:
reatly appreciate some opinions.This is a 240V residential service conductor and master circuit breaker. The load is unknown (a few lights, fridge and furnace running) The temperatures do not appear hot but there is a noticeable temperature gradient. Normally it looks more consistent along the length of the wire. Could this be a termination problem or faulty breaker? Also, does anyone have any suggestion as to how much greater the temperature of the conductor would be compared to the insulation?
Thanks
You didn't put a spot on the hot part of the breaker but the scale indicates the upper end to be ~80 deg. F. This may not be very much above ambient but of course the actual source may be much hotter. The question is what is the heat source? Besides the obvious possible loose connection, it is possible that the breaker contact points have become pitted making for a poorer internal connection. My worry is that these contacts can heat up enough to melt & weld together. Then when needed to open during a fault condition, they fail to interrupt the fault. If this breaker has a history of tripping, replacement may be needed.
 
Re:Electrical service Pierre1234 5/5/2010
I would suspect that you dont have any problem here, simply more current in one wire than the other. You have to check the current to be able to determine a problem. Without current reading all you will have is speculation.
 
Re:Electrical service fazlye 5/5/2010
Dear Darby,

from my experienced, nothing to be worried here, but just check the termination to ensure that its tighten properly and do few more scanning on regular interval just to make sure wether there is any temperature rises in the future. and jvoilt i totally agree with you.
 
Re:Electrical service zury 5/5/2010
For me seam like the termination need to be tight
enough as you see the side of the breaker shown more hotter then the aother and the cable also shown hotter as well.Or may be your load at that cable is higher then other phase,you shoud measure the ampear to determine the load balance.
 
Re:Electrical service nam 5/6/2010
I have scanned numerous panels and in my experience this does not appear to be that hot. However, it is very important to know what the load is at the time of the image. You should also scan the neutral connections. Under normal circumstances the side of the breaker always shows more heat. It is worth de-energizing and checking the termination. Don't just tighten it though, disconnect the conductor and check the integrity of the conductor and breaker termination and clean it up if necessary. Always be aware of the electrical and ARC FLASH hazards associated with performing IR scans on electrical equipment.
 
Re:Electrical service Magnumguy 5/6/2010
First I would want a current reading of each leg just to find the loading, but looking at the thermogram there is heat dissipating going away from the breaker, and I don't like the look of the breaker connections to the bus, I would be checking them. To be honest I would get this breaker out of there and I agree with nam, be very very aware of arc flash, this is an area for a licensed sparky for sure.
 
Re:Electrical service Laland 6/5/2010
Please check what are the actual connected loads. You mentioned Fridge, so it must have been connected through a convenience outlet. Ther should be separate CB's for lighting and outlet.

My little comment..
 
Re:Electrical service Pete 6/17/2010
Good catch on the temperature drop along the conductor. Any time I see a temperature drop on a conductor I suspect a Thermal Anomaly. In this case I suspect the internal contacts of the breaker.

My reasoning: The internal temperature of the breaker should be close to the conductor temperature. Plus the temperature of the conductor should be consistent along the length of the conductor (current flow is current flow). Look the the load side and bus side screws slots (slight cavity effect). The bus side shows an elevated temperature compared to the load side. If the viewing angles were different, between the two screws, I would say reflection might be the cause. Since both screws are shown at the same angle that can remove the reflection arguement.

We recently replaced a breaker due to a tempature signature similar to yours. Root cause analysis showed a contact resistance > 800 micro ohms.

Don't use the upper breaker for any kind of comparison. If it were gone I would still suspect the bottom breaker for the reasons I referenced above.
1) Temperature drop on the conductor.
2) Internal temperature compared to the conductor.
3) Temperature in the bus side screw slot.

At the minimum I would continue to monitor. JMHO
 


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