Ambient Temperatures

[kda3310]

I have tried to explain something I do not fully understand myself. I work in an area that the air temperature can get up to 50 - 55 Degrees Celsius. I just over sizing the conductors and breakers to a size I know will work from experience to make up for the ambient temperature factor. What is the proper way to calculate for ambient temperatures?

 

[haskindm]

Ampacity adjustment factors for ambient temperature for conductors are at the bottom of table 310.16. I don't know how (or if) you would derate a breaker for high ambient temperature. Most breakers are designed and tested for 40 degrees C. I am not sure that anyone knows exactly how they would react in higher ambient temperatures. There may be breakers available that are designed and listed for higher ambient temperature, but I have not seen them.

 

[kingpb]

Yes, equipment is typically designed for 40 deg C. Higher temperatures will need to be considered. The manufacturer needs to be consulted, and should be able to provide information regarding derating due to higher temps. This can become a big problem if you are using any electronic relays, although I believe some are noe capable of 50 deg C. You would need to check manufacturer data sheets.