temperature rise of a fully loaded breaker terminal

[Andy32821]

Anyone know what the normal temperature rise of a fully loaded breaker terminal should be? I understand that the connection is (in most cases) rated to work safely up to 75 Degrees C.

I need to infrared scan hundreds of misc lighting and power panels mostly consisting of 20 amp branch circuits. Ideally I would remove all the panel covers to do this. But with limited resources that is no going to happen.

Instead I would like to use a threshold value of a breaker face being above adjacent breakers. Right now I am using 20 degrees C rise. If a breaker is 50 C and most of the other breakers in the same panel are 30 C I tag that panel for inspection. (Pull cover, check breaker terminal tightness, visually inspect wiring, and check loads.)

I need to know what temperature rise would be normal on a 20 amp breaker at a 16 amp load over the same breaker with no load. Also would the same temperature rise apply to larger breakers? They have more load, but also have larger connection areas.

I assume breaker designers have a temperature rise target for normal maximum load that is well below the safety limit of 75 degrees C.

Thanks,
Andy

 

[itsmoked]

I don't think there is going to be a front-of-the-breaker temp rise you can use. You will probably need to just set your own standard for that. By examining a CBs body temperature under the cover after noting its face temp, right after opening the door cover.

 

[JBD]

The terminals of breakers are always rated below the temperature rise of their conductors. For example it would not be unusual to see 20A breakers rated for a 50C rise when using 60C insulated wire and a 55C rise with 75C conductors.

Also, it it not unusual for the terminals to normally be "cooler" than the breaker handle.

 

[waross]

I think the method you are working with will give you good results. I suggest that when you remove the cover that you scan all connections before tightening or disturbing them. Then do some checks with your ammeter. You will soon develop a feel for normal temperatures and abnormal temperatures. By the time you finish this project you will be the expert. I hope you will have time to share a summary of your results with us.
yours