hot (to the touch) electrical wire in panel

[iron]

we heated with wood all last winter. this april, we fired up the furnace (electric) and it started tripping the 70 amp breaker in the panel. there is also a 60 amp breaker on the furnace itself, but that has not tripped.

i've had 2 HVAC techs come over. one gave me a salesman pitch and said screw you (more or less). the other seemed very genuine, worked hard and long to troubleshoot, and basically tested nearly everything in the furnace itself. at the end, we found ourselves heading back to the breaker box. it's a 70 amp, 2-pole breaker. one of the lines coming in was cool to the touch. the other line was hot. the voltmeter read 135 degrees on it. voltage reading was variable and erratic. we noticed that the screws in securing the wire to the panel were a bit loose, so those were tightened. i haven't run the furnace yet to see if that solved the issue. if it doesn't, does anyone have thoughts as to what it could be?

extra background: the panel and all breakers are brand new. my electrician friend installed them a year+ ago. we haven't really used the furnace much since that went in, so part of me suspects bad breaker. i don't know...

 

[Highbeam]

we heated with wood all last winter. this april, we fired up the furnace (electric) and it started tripping the 70 amp breaker in the panel. there is also a 60 amp breaker on the furnace itself, but that has not tripped.

i've had 2 HVAC techs come over. one gave me a salesman pitch and said screw you (more or less). the other seemed very genuine, worked hard and long to troubleshoot, and basically tested nearly everything in the furnace itself. at the end, we found ourselves heading back to the breaker box. it's a 70 amp, 2-pole breaker. one of the lines coming in was cool to the touch. the other line was hot. the voltmeter read 135 degrees on it. voltage reading was variable and erratic. we noticed that the screws in securing the wire to the panel were a bit loose, so those were tightened. i haven't run the furnace yet to see if that solved the issue. if it doesn't, does anyone have thoughts as to what it could be?

extra background: the panel and all breakers are brand new. my electrician friend installed them a year+ ago. we haven't really used the furnace much since that went in, so part of me suspects bad breaker. i don't know...

Breakers go bad and are cheap and important. The installation error could have ruined the breaker. Change the breaker and inspect the wire end to be sure the loose connection didn't cause arc damage. Erratic voltage indicates a crappy connection somewhere.

70 amps is big. Aluminum or copper wire? Disconnect at the furnace and see if voltage stabilizes.

 

[Ashful]

Ditto. Heat means power dissipation, and power dissipation is i^2 R. Now, in the absence of a ground short, the current in both wires should be equal, pointing toward high R. The erratic voltage also points toward high R = V/I.

HighR usually means a loose or corroded connection. Tighten all connections, and replace anything that might have been damaged in the process.

 

[fbelec]

if it's a square d homeline panel the breaker is most likely junk. i see nothing but issues when i get called in and there is a homeline panel. most likely a loose connection at the breaker. sometimes the screw that clamps down on the wire is screwed up from the factory. the screw feels tight but it is not on the wire. shut the breaker off and try pulling the wire out of the breaker if it is loose or comes out there is your problem. see if you can find a amprobe and see what the thing is drawing for current. like others said most likely the 70 amp breaker is toast.

 

[begreen]

A loose wire connection can cause those issues. I'd probably replace the breaker. While it is out, look at the bus bar that it plugs into for any discoloration or corrosion. And check all other breaker connection screws for tightness. Then check the other end where the wires enter the breaker on the furnace too.

 

[sportbikerider78]

Yup...breaker is the cheapest place to start. I'd skip the HVAC help and focus on electrical help. The HVAC guys aren't the best to troubleshoot issues like this.

 

[Hogwildz]

I'm thinking if it was on the heater side, the 60 amp breaker would trip before the 70 amp panel breaker. Issue def at the panel.
If it is a Federal Pacific panel with stab-loks, get rid of it, they are a known hazard.