Originally Posted by ALJO
In short I will explain how the electronic operated Atwood furnace works.
The thermostat (TH) turned up and switch on the TH in ON position calls for heat; which in turn tells the furnace to fire up (high limit ON)
The fan will start and blows cold air. The same fan is hooked also to the combustion fan which in turn clears the burning chamber from any gasses out through the flu pipe (is called purge cycle). After approx. 60 sec. when all the electronics switches are in line it will tell the gas valve to open and ignite on the same time.
If there is air in the lines the furnace will trip and you have to reset the TH switch to of and then the above cycle will repeat. In order to speed up this process; after you turn on the LPG at the bottle (do this slow) then light first your stove burners. Turn the burners off after there is a normal flame. After this in most cases the furnace will start after the first try.
When you feel the heat coming from the registers the furnace will trip the high limit switch which turn off the furnace burner. If the TH still calls for heat the furnace burner may come on even if the blower fan is still running.
If you think your furnace is cycling too much you have to adjust your TH (follow the instructions manual from the TH)
The furnace has usual 4 discharge outlets (4 x 12 sq.in = 48 sq.in) Return air is minimum 65 sq.in and recommended is 80 sq.in) (8516 and 8520) Check for pinched discharge hoses this can be a cause of overheating and trip the furnace operation in to fault code. The blower fan has its own cycle switch.
I would recommend to read the manual if you have troubles. If you donít have one; download one from Atwood.
That is a good discription of the operation of the furnace. And a couple of good troubleshooting tips.
The thermostat I have is a hot/cold electronic with NO delay adjustment. What you are referring to is an adjustment in mechanical thermostats that adjust the cycle time. The furnace can run longer less frequently or shorter more frequently. Helps adjust the large temp swings you get in a small under insulated trailer.
However only under the most extream temp conditions will the thermostat call a shutdown, and then recall a startup in less than 1 - 2 mins causing the burner cycle but no fan stoppage.
In the case of my furnace it is NOT the thermostat making the call. The dealership confirmed it and even replaced my stat. They agree its not getting proper airflow, they change the ducting arround and then put the grill back on crimping the duct hose in half. I am sure that I am not the only person with this problem and the others describe the exact same thing. If you have anything less than (2) 4" unobstructed ducts with NO 90 degree bends you are not getting proper air flow AS PER MANUAL! Adding a few 90s may still work but will degrade the life of your $850+ dollar furnace by years!