How hot is too hot?

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tonype

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When reviewing a breaker panel, I use an infrared thermometer to take a quick check of temps. Today in a diner, a 2-pole 20-amp breaker (Cutler Hammer) for some item in the kithcen was about 150 degrees F. Never came across this high. Is there any guideline on what may constitute a problem?
 
I'm not a electrician...


Stick a amp meter on there and see how much the circuit is drawing. That would be a starting point to see if there is even a problem.
 
I would think your temp is too Hot that close to 70deg. Is the breaker hot to the touch? You need to check the connections, the amperage , the buss.

If all is good then the breaker is failing in my opinion.
 
What is the normal operating temperature of a standard breaker when all connections are good and it's operating near it's maximum ampacity? Without knowing that I don't see how anyone can answer the question.
 
Assuming it was applied and installed correctly, common molded case circuit breakers (MCCB) at rated current effectively permit a maximum operating temperature of 90?C (194?F) in a 40?C (104?F) ambient.
 
Sierrasparky said:
I would think your temp is too Hot that close to 70deg. Is the breaker hot to the touch? You need to check the connections, the amperage , the buss.

If all is good then the breaker is failing in my opinion.
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Breaker was hot to the touch.

As an Engineer/inspector, I do not stick stuff in panels - leave it to you guys who are trained for this. Playing on the safe side, I will advise client to have an electrical contractor review this.
 
rbalex said:
Assuming it was applied and installed correctly, common molded case circuit breakers (MCCB) at rated current effectively permit a maximum operating temperature of 90?C (194?F) in a 40?C (104?F) ambient.
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I have never seen a 90?C rating for any part of a molded case breaker. As I recall the operating handle is only allowed to be at 60?C.
 
jim dungar said:
I have never seen a 90?C rating for any part of a molded case breaker. As I recall the operating handle is only allowed to be at 60?C.
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You're right and thanks for the correction Jim. I shouldn't answer questions from old memories. 60?C (140?F) would still be very warm to the touch and could easily cause a second degree burn under the right conditions. Nevertheless, a 150?F reading is excessive under any conditions.
 
rbalex said:
You're right and thanks for the correction Jim. I shouldn't answer questions from old memories. 60?C (140?F) would still be very warm to the touch and could easily cause a second degree burn under the right conditions. Nevertheless, a 150?F reading is excessive under any conditions.
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For the trivia people.
Based on the NEMA standard AB-1-1986 (yeah I know its old).

Maximum Temperature rise limits above rated ambient at 100% load:
Contact parts, copper - 45?C
Metal parts - Limited solely so that damage is not caused to itself or insulating materials
Main operating means, parts of insulating material - 60?C (based on 25?C ambient)
Main circuit terminals for external connections - 50?C

If temperature rises on wiring terminals exceed 50?C, the manufacturer shall specify conductors with 90?C insulation sized using the 75?C ampacity.
 
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