|
QUESTION:I am in the process of buying an older home in South Carolina. The
heating system is an older gas furnace, forced hot air type. I'm not
very familiar with gas furnaces. The owner must provide a letter from a
certified HVAC contractor regarding the state of the funace.
Can somone give me some ideas what the most common problems are in older
furnaces that I should be aware of. Primarily, I am worried about the
integrity of the HX, and that it doesn't leak CO into the home.
ANSWER: I don't work on HVAC for a living, but I can tell you about the furnace
at my parents' house. It's a Lennox and original to the house -
about 35 years old now. The main maintenance items have been thermocouples,
a fan relay, and a couple of fan motors. (It's on its third fan motor
now - the second replacement).
The thermocouple goes in the pilot flame and provides an electrical
signal to the main gas valve to keep it open. If the pilot goes out,
it shuts off the gas to the furnace. But thermocouples also quit
working, which also shuts off the gas. Most hardware stores carry
a good selection.
The fan relay goes between the low 24v thermostat/control wiring and
120v line current for the fan motor. The one on their furnace would
stick on and require pounding on the side of the furnace to unstick
(so the motor would shut off). Finally they replaced it. They are
pretty cheap, maybe $10 at a local distributor. Or, replace it with
a solid-state relay for $25 or so and never worry about it again.
The fan motor runs the big blower in the bottom of the furnace. Some
of them have oil cups on the ends, which you should oil at least
once a year. Even so, nothing lasts forever. Again, a local
HVAC distributor or somebody like WW Grainger should be able to
provide a suitable replacement.
Oh yeah, don't forget to change the filter.
Note, these are not the *only* things that can go wrong! But these
are the things I've experienced going wrong the most often. Sample
size of 1, so your mileage may vary.
|
|
|
|
