| Title | By | Posted On |
| Electrical breaker temp ratings |
cdeery2 |
4/11/2008 |
I'm trying to obtain any information on electrical breakers as far as the heat threshold of the breakers. With an 80% max threshol load applied on any given breaker 120/208v what would should a typical temperature range be in. After the typical temperature range is exceeded I would assume that the breaker could possible have an internal fault, arcing bad connections.
Any thoughts or theroy's.
Thanks |
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| Re:Electrical breaker temp ratings |
cdeery2 |
4/11/2008 |
cdeery2 wrote:
ing to obtain any information on electrical breakers as far as the heat threshold of the breakers. With an 80% max threshol load applied on any given breaker 120/208v what would should a typical temperature range be in. After the typical temperature range is exceeded I would assume that the breaker could possible have an internal fault, arcing bad connections.
Any thoughts or theroy's.
Thanks I wanted to state that I'm looking at a 100A 3 phase 120/208v breaker at an average of 68-70 A per phase and reading a temperature of 110 F on this breaker. |
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| Re:Electrical breaker temp ratings |
HITECHSOLUTIONS |
4/12/2008 |
| First of all you should be reading in the celsius degrees. All electrical components are based on celsius. NEMA has a standard that they use, and you can too. Or you can use what the facility wants to use. Also you need to know the ambient temp, the reflected temp. Can you give us a pic? |
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| Re:Electrical breaker temp ratings |
IRJay |
4/14/2008 |
UL489 states a breaker terminal area should not have a rise from ambient above 50 degrees C. You could apply this to the entire breaker as the material is all the same. This is a different rating than the terminal rating of 60 or 90 C which is a rating to determine wiring derating. Note here that this can result in allowable breaker temps above 190 degrees F.
I generally am concerned on breakers if the temp is above touchable temp of 130 F or 55 C. This is my rule of thumb. I would never want my breakers to be above the wire insulation temp rating. |
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| Re:Electrical breaker temp ratings |
Douglas |
5/9/2008 |
HITECHSOLUTIONS wrote:
f all you should be reading in the celsius degrees. All electrical components are based on celsius. NEMA has a standard that they use, and you can too. Or you can use what the facility wants to use. Also you need to know the ambient temp, the reflected temp. Can you give us a pic? Just a quick comment "all" Square "D" type circuit breakers are "rated" on the side of "each" device 40 c, i would suggest that " tempature above that is a concern because that rating noted on the plastic body of the breaker...so if there is a tempature rise of more than say 10 per cent of that rating of 40C it may appear to do a follow up on the issue. Peace Douglas |
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| Re:Electrical breaker temp ratings |
Ea1Services |
5/9/2008 |
| Interesting thread as the question posed has been troubling me as well. It seems that one step here would also be to reduce the reflective capability by the use of non reflective electrical tape. Would this give a more accurate reading? |
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| Re:Electrical breaker temp ratings |
jvoitl |
5/9/2008 |
1. The 40C rating on the side of a circuit breaker has nothing to do with the temperature of the breaker itself. It is the ambient temperature rating for the air around the breaker at which the current rating of the breaker is based. A higher air temperature can affect the trip characteristics of the breaker.
2. These breakers are thermal/magnetic. That is they have a magnetic funtion that will trip them with a short circuit, and a thermal function that trips them on an overload. By design they generate heat and that is not a defect.
As with any indirect temperature measurement the surface temperature of the breaker does not indicate the correct internal temperature. The only way to check if it is too hot is to compare it with another identical breaker under the same load and ambient conditions. When checking breakers the important thing is to check the line and load side connections. If they are under a pretty good load the breakers themselves will always be warm, sometimes way above 40C.
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