furnace duct redo - found $560
my front furnace would only run a few minutes before it would shut off at 200* air temp, so I decided to replace the ductwork that was old and no longer flexible. I cut away a choke point in the wood divider and found out where my HWH level was located. After replacing ductwork furnace was quitter and ran about 50% longer before it would shut down at 200*. In the fore shot you can also see my new $31 pressure tank that is now constructed of stainless steel. The way furnace was originally running it probably would not exceed 50% efficiency. Sunday was warm so I opened up the external furnace access to discover that the fan inlets were blocked. The aft inlet was blocked by the fan motor, and the fore inlet only had about 1/4" clearance to the control board. The furnace also had a tag that showed 110-130* temperature rise with only 0.1" of static pressure which isn't didley squat to start with. Took the control board out and noticed the screws holding it to the slide in assembly were installed wrong and causing the thing to stick out another 1/4". re-instertted the screws from the backside and now the clearance is 1/2" as shown in the "intake" picture - somewhat better, and if I would of had some plastic spacers I could modify the control board and gain another 1/4". After this mod the furnace would run about 70% longer before shut-down and even more quite, so I am making progress.