Aire Flo Model# AF90-MPB075U3A
- It has been converted to LP (propane)
- Inducer is installed vertically
- Furnace is direct-vented horizontally through the basement wall
- I seem to have good air flow through the exhaust
On to the issue at hand: we have no heat
When the thermostat calls for heat, nothing happens. I have tried performing the shut-down and start-up sequences as written on the furnace label. When I restart the furnace, it initially displays the "heartbeat" LED code indicating normal operation. Then when I call for heat, the LED code indicates "Pressure switch CLOSED, should be open"
After receiving that code, I followed the shut-down procedure. First I turn down the thermostat, then turn off the gas control switch. When I turn this off, the inducer starts running almost immediately. It runs for 20-30 seconds, then stops. At this point, the LED fault code changes to "Pressure switch OPEN, should be closed"
I am going to try some of the methods found on other posts regarding the pressure switch (e.g. blowing on the hoses, etc.).
I have been unable to locate a manual for this furnace (if you've got one to share, I'd be tickled pink), but I found one for a similar model that warned about installing the hoses in a manner that would form a trap in the hose. It recommended trimming the hoses to avoid this situation.
From what I can tell, both of the hoses connected to the pressure switch have a loop with a low point that could form a trap. In fact, when I disconnected them the one from the combustion area did have liquid in it. Did the installer make a mistake when putting these in?
I'm tempted to trim them to try and eliminate the potential for traps, but I'm not sure this is possible given the configuration of the pressure switch. It is mounted on the inducer, and the hose connectors point downward. The drainage hose from the combustion chamber (at the top of the furnace) must come down to where the pressure switch is, and then go underneath it and turn upwards to make the connection on the bottom of the pressure switch. Is this installed in the correct fashion?
I'll try to put up a photo later if I can. In lieu of that I made a quick drawing of the furnace.
THANKS IN ADVANCE FOR ANY IDEAS OR ADVICE!