kid_stevens
Senior Member
- Location
- Albuquerque, NM
Why do we have 90c wire and only 75c or less terminals? Makes no sense to me after all these years.
This near accident brought this to mind. A customer called and said his dryer, Stove and hvac breakers kept tripping.
I checked voltages and one side of the 240 was at 198 and the other was at 236.2 on the meter. I called PNM for an emergency fix and kept looking. The Dryer breaker had the same voltages but the lower leg at the breaker wiring terminals was at 300c and the higher voltage was at 80c. That alone says the devices stand up to more heat than the ratings allow.
After PNM fixed the problem at the tap I checked and the temp dropped to 210c. Pulling the wires I checked for the aluminum to be brittle and failing but they were not, so I no-Oxed them and tightened them with a small inch pound torque wrench so that both terminals would have the same tension and both terminals dropped to 75c.
Still 15c above the old QO breaker's 60c rating.
So why isn't new equipment rated for the 90c wire we install by default?
This near accident brought this to mind. A customer called and said his dryer, Stove and hvac breakers kept tripping.
I checked voltages and one side of the 240 was at 198 and the other was at 236.2 on the meter. I called PNM for an emergency fix and kept looking. The Dryer breaker had the same voltages but the lower leg at the breaker wiring terminals was at 300c and the higher voltage was at 80c. That alone says the devices stand up to more heat than the ratings allow.
After PNM fixed the problem at the tap I checked and the temp dropped to 210c. Pulling the wires I checked for the aluminum to be brittle and failing but they were not, so I no-Oxed them and tightened them with a small inch pound torque wrench so that both terminals would have the same tension and both terminals dropped to 75c.
Still 15c above the old QO breaker's 60c rating.
So why isn't new equipment rated for the 90c wire we install by default?