The AC unit is about 15 years old and is an all in one unit outside which has the gas is feeding into it. Just recently, when the flames ignite, we can hear a low rumble/banging noise coming from the unit. If this helps as to what it sounds like, my wife though I had shoes in the dryer. The sound is a bit more muffled than that though. I went outside and it sound like is air blowing over the flames kind of like you'd hear in one of those tubular portable propane heaters. A) Could this just be dirty nozzles? B) Would that possibly allow air to mix with the natural gas as it's burning and make that sound? The instant the gas goes off (with the blower still running) the noise stops. C) Is there any risk to continue running the system until someone comes out? It's only in the teens this week.Thank you
It sounds like preignition of the fuel to me. Gas vapors are building up before ignition which is probably the result of a faulty nozzle, just like a carb you are getting to much because of a faulty nozzle, partial obstruction of the nozzle or worn nozzles and yes it would definitely sound like that. Preventative maintenance by a qualified serviceperson before heating begans would let you sleep better at night.
The heat exchanger is probably clogged with carbon causing the gas flame mixture to flash back outside the exchanger.Check to be sure that the exhaust flue is not obstructed. As for danger if I run across one doing this I clear my schedule to clean it properly. It is not safe.
DO NOT use it! It sounds as if your exchanger could be cracked letting carbon monoxide in the house. This WILL kill your family! Call a pro asap! 20 yrs exp - houston texas
