I'm hoping someone has an idea of what's going on with my furnace. I have a Trane gas furnace in my home, which serves as the emergency backup to a new Rheem heat pump I had put in over the summer. The furnace is 10 years old, and had been working fine prior to the heat pump installation - just a bit expensive to run.
When winter rolled around, and the furnace started to kick on occasionally when the temperature got too low outside, I started smelling a small whiff of gas coming out of all of most of the registers in my home. It only happens just as the furnace kicks on.
I called the company that installed the heat pump. They came out, looked it all over, bubble soaked the lines, and couldn't find anything wrong. I called another company who came out, removed the burners, inspected the heat exchanger, and suggested that the heat exchanger must be leaking, and charged me $200 for the "diagnosis". They then came back out and replaced the heat exchanger a week later, apparently still under warranty (surprisingly cool of Trane), for another $500 in labor.
Now, every time the furnace kicks on, I get a faint whiff of gas. Same as before, just $700 poorer.
Does anyone have any idea what could be wrong? To repeat the facts:
-New heat exchanger,
-All gas lines bubble-soaked, no obvious leaks
-Only smell gas just when the furnace kicks on.
-Gas smell is coming into the home through the registers, in multiple rooms (strongest in the registers closest to the furnace)
-House was built in 1997, there's no fresh-air intake to the hvac system (closed loop), no obvious air leaks in the ducting around the furnace.
I'm at a loss. Does anyone have any suggestions???