I got a call today regarding a rooftop breaker tripping. It is at a restaurant with a subpanel on the roof that feeds two ac units and some smaller exhaust fans. The breaker that feeds the panel is tripping every once in a while. twice yesterday, none today. I checked the amperage at about 6:30 this evening with both ac units running. It was pulling 75 amps on a 90 amp breaker and the wire was quite warm. It has #2 alum wire feeding the panel which runs for about 45ft in pvc on a white rubber room.
Could the acs running when its 90 degreees, with the increased ambient temperature cause the breaker to trip? I know that it could cause detioration of the wire. I did change the two 60 amp breakers on the ac out last year at this same time beacause they were crumbling from being to hot.
When I go back up there I will take a picture. Somebody from the kitchen opened up the enclosure door for air and bent an aluminum pan over it to make it raintight. The other panel opens up. They propped it up with another pan. I will look into the fans for the panel. Thanks Reno.