My Amana AMVM96 115, 000 variable speed furnace only operates when the top panel is off. I have had four technicians exam the unit, but none of them has been able to get the furnace to operate with the top panel on. Here is the -
The unit was purchased and installed in early December 2012. The furnace was installed in a house which was undergoing major renovations.
Problems with the unit began when my plumber (not an HVAC specialist) turned off the furnace to search for a gas leak. After my plumber turned the furnace off, the unit failed to restart. The installer sent a technician to service the furnace. The technician gave the unit a cursory inspection, turned the unit on, and went on his way.
I moved into the house in February. When I moved in, I discovered the intake/exhaust vents knocked together, or “oil canned”. The “oil canning” was rapid, loud, and occurred when the furnace entered recovery mode.
House renovations were completed in March. The furnace sounded sick. I lost another furnace to a previous renovation, so I decided to have my brand new unit serviced.
I was dissatisfied with the installer and I hired another technician to clean the unit. After he cleaned the unit, the service technician mentioned the installer hadn’t properly wired the furnace (the installer’s technician admitted the poor wiring job during the previous service call when my plumber turned the furnace off and it failed to restart).
The technician restarted the furnace with the top panel off, closed the unit, and left. At some point, the unit shut itself off.
The service technician who cleaned the unit returned and was unable to diagnosis a problem. The same cycle happened again; the technician restarted the furnace with the top panel off, closed the unit and left. Again, the furnace shut itself off.
For a third time that day, the technician visited trying to diagnosis the problem. He recommended rewiring the unit to remediate the installer’s errors. Also, he believed the shut off problem related to a malfunctioning pressure switch. When I woke up the next morning the unit was off.
I called another HVAC contractor who was highly recommended by my electrician. He was unfamiliar with the module and declined to work on it.
I called back the previous technician and he suggested trying to operate the furnace with the top panel off until he was able to revisit my unit. With the top panel off, the furnace seemed to operate normally.
I agreed to the let the technician replace the pressure switch and rewire the unit per his recommendations. He performed what he believed to be the necessary repairs. If I had to guess, I would say the technician rewired the unit in a workman like fashion.
Similar to before, the unit worked for a few hours with the top door sealed and then cycled off. The rewiring occurred on a Friday. I called the technician on a Friday evening. He directed me to try to restart the unit with the top panel on. I observed that the unit began the startup cycle but shut itself down just before it should have powered up.
He directed me to restart the unit and operate the furnace with the top panel off. With the top panel off, the unit operates without incident. It should also be noted that noted that the previously mentioned “oil canning” subsides when the top panel is off. The diminished “oil canning” suggests the furnace is drawing some of its oxygen supply from the room in which it is situated.
With the top panel on, I pieced together that the unit seemed to shut down when the furnace was scheduled to enter its recovery mode. Instead of entering recovery mode, the furnace went cold.
The technician returned several days later, examined the unit, and reread the installation manual. He determined the intake/exhaust lines were to close together and he reconfigured the intake/exhaust line to meet Amana specifications.
Also he examined the intake line for obstructions but found none. Further, he noted the furnace “pinged” when operating with the top panel door on. He believed these “pinged” indicated the furnace might be oxygen deprived.
He also measured the length of the intake run. He noted that my air intake run was just under the maximum length recommended by the manufacturer. As we reside in Colorado, he wondered if the recommended air intake length should be shortened to compensate for the altitude. The technician called Amana tech support, who informed him the length air intake run has been lengthened/revised upward and it shouldn’t be the cause of my problem. The technician has told me that he has consulted with Amana, as well as other technical resources to try to diagnosis the problem. No one has given him any insight into what may be causing my furnace to shut down.
After he left, the unit functioned for a day before it shut itself off. The shut off cycle was similar to all of the other previous incidents.
At this point the technician is out of ideas.
He has suggested installing a fresh air supply to furnace and my tanked hot water heater, which is directly adjacent to the furnace. There is no fresh air supply in the furnace room, and the furnace shares space with a 40,000 BTU tanked water heater, and a radon mitigation system.
However, I find my technician’s fresh air supply proposal to be incomplete. I understand the fresh air supply is mandated by building codes in many municipalities (including mine). I have no problems installing a fresh air supply if it fixes the furnace issue but I don’t want to bust a hole in my basement wall if it does not fix the problem. The house is 70+ years old and hardly air tight. Also, by installing a fresh air supply he wants to abandon the outside fresh air intake line in favor of drawing the furnace’s air supply directly from the room. He says this installation scenario is permitted by the installation manual. It should be noted the current fresh air intake line can be shortened considerably.
The furnace room is approximately 450 sq ft and has 8 ft tall ceilings. I found a calculation online which suggests the air supply in the room is woefully insufficient for a furnace drawing air from the house, but shouldn’t my sealed furnace draw most of its combustible air from the outside through the air intake line? How much air does my sealed furnace need from the furnace room? Also, a couple of other online contributors mentioned removing plastic plugs from the furnace’s sides to increase oxygen flow in to the unit but I can’t figure out if this is an option for me. I understand all the implications of removing the plastic side plugs; i.e. need to for greater fresh air supply, etc.
Obviously, the thrust of this post suggests the furnace’s problem is related to poor air supply but the focus on air supply could be wrong. Any advice at solving this problem would be greatly appreciated.