Wednesday, March 9, 2011

Thermal fuses: Often the symptoms, rarely the problems

* I would tell you not to try this at home, but that's pretty much the only place you can try it. So I will tell you to turn the power off at your circuit breaker panel if you decide to try this at home.

** Turn the power off at your circuit break panel if you decide to do this at home.  If you don't, then you might as well consider this to be a manual on how to possibly kill yourself.

*** I really didn't set out to create that kind of manual, so turn the power off at your circuit breaker panel if you decide to do this.

Late last fall, I noticed that the air coming out of our heat registers was not overly heated when the auxiliary heat strip—the heat element located inside the furnace—was called for by the thermostat. When the day came that it took the furnace more than three hours to bring the house up to 70 degrees from 62, I decided it was time to figure out what was going on.

Being an inspector, my first action was to measure the air temperature as it came out of the heat registers, and to compare that reading to the temperature at the cold air return register. With the house temperature at 70, the cold air return measured right around 70.  That makes sense.  Unfortunately, the air gently coming out of the heat registers was only a few degrees warmer. When the heat strip was working properly, that air had previously been around 120 degrees. Obviously something was amiss.