Hot Breaker

Status
Not open for further replies.
A

almcvay

Member
I'm in hopes someone can can help.
First I'm not a home owner. I have a master lic. in 9 states. This one blows my mind.
I was called to check a roof top A/C unit 208 3 phase. 3 # 6 thhn copper in 3/4 emt
about 75 feet of pipe. The breaker is very hot 115 deg. inside a cool store.
The breaker is 40 amp and does not trip. The unit draws 28 amp all phases. 210 volts at the A/c unit. I replaced the breaker with a new one. Same as above. Very Hot! The buss looks great and is copper. The old breaker was tight. My question is why is it still Hot?
Thanks Leon
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I don't think 115 degrees is that excessive. What are the loads in the circuits that are close to the a/c breaker? Why were you called to check the a/c- was it because of the heat?
 
mcclary's electrical

mcclary's electrical

Senior Member
Location
VA
just started playing with your new laser temp gun, huh?

that's not excessive, and as long as everything is tight, and the breaker is not tripping, you have made up an imaginary problem
 
480sparky

480sparky

Senior Member
Location
Iowegia
115?F isn't very hot at all. The breaker should be capable of cranking out 140 all day long.

If you're concerned about it being a fire hazard, The entire city of Phoenix should be ablaze right now.

115?C.... well, I'd start getting concerned.
 
A

almcvay

Member
No I'm not playing with a new gun. This is the HOTTEST spot in the panel. I was called to the store to install a new light cricuit. the Store manager stated the A/C did not work good. I stated the A/c breaker was warm. She called the main office thay ask me to replace it. This 115 deg F. is 25 deg. hotter than the rest of the panel. And yes it was torqued. The load on this breaker should not have this high temp.
 
mcclary's electrical

mcclary's electrical

Senior Member
Location
VA
almcvay said:
No I'm not playing with a new gun. This is the HOTTEST spot in the panel. I was called to the store to install a new light cricuit. the Store manager stated the A/C did not work good. I stated the A/c breaker was warm. She called the main office thay ask me to replace it. This 115 deg F. is 25 deg. hotter than the rest of the panel. And yes it was torqued. The load on this breaker should not have this high temp.
Click to expand...

Don't worry, I was only joking:grin:. With that being said, If I opened up a panel this time of year, I would certainly expect the A/C to be one of the hottest breakers in the panel. Did you perform a FOP test on the old breaker before changing?
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
ptonsparky said:
The breaker is sized at minimum. I personally think a 40 is a bit close for a 28 amp load and would use a 50 or even a 60 depending on the Max allowed by the unit label.
Click to expand...
I doubt a 50 or 60a breaker would actually run any cooler, but it's possible.

I agree with McC that the FOP would have been a great first test.
 
480sparky

480sparky

Senior Member
Location
Iowegia
almcvay said:
No I'm not playing with a new gun. This is the HOTTEST spot in the panel. I was called to the store to install a new light cricuit. the Store manager stated the A/C did not work good. I stated the A/c breaker was warm. She called the main office thay ask me to replace it. This 115 deg F. is 25 deg. hotter than the rest of the panel. And yes it was torqued. The load on this breaker should not have this high temp.
Click to expand...


Are you going to panic at every 'hottest spot in the panel'?
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
almcvay said:
The load on this breaker should not have this high temp.
Click to expand...
How do you know?

A standard breaker is calibrated to carry full load at 104?F ambient temperature (when not in an enclosure). So your breaker is probably not even near its overall operating temperature. Did you check the ambient temperature of the panel?
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
hurk27 said:
Just had a Long John Silvers with a roof top unit on a 60 amp 3-pole breaker, that was about 122 deg. F changed it out and the new one ran about 109 Deg F, but neither one ever tripped.
Click to expand...
You probably would have obtained the same improvement by removing and replacing the same breaker, and remaking the terminations.
 
Status
Not open for further replies.
Top