Here is the back story:
- Starting to finish basement, needed to exhaust my furnace outside
instead of drawing in air for combustion inside the house. Hired
HVAC person to do this in the fall. - Winter arrives, I go to run furnace, first really cold day and the
furnace won't start up (an Armstrong Air unit) that is 8 years old. Error codes tell me: "pressure switch open with inducer on". - I call up same HVAC person. There is no report, but he determines
that my exhaust motor is the culprit. It is replaced. They do not
replace the pressure switch or give me any diagnostic reports or paper work. The repair costs me $600 (that is the
cash deal). Tells me that it includes parts warranty and labour
warranty for a year and to call him if it happens again. - Furnace starts running for 10 more days. Gets really cold again, and
furnace stops working again with the exact same error code. Same
HVAC repair person comes back and tells me that my heat exchanger is
cracked without opening anything up within 20 min of being here
(based on the flame at the burner) and tells me the entire furnace
needs to be replaced. - He leaves with the furnace running again after simply disconnecting the
air intake pipe from outside, saying I can leave it off until I decide on
which new furnace I want to install and gives me the fear mongering
talk about CO2. He also wants to sell me a refurbished furnace that he has, or offers to sell me a new Payne unit which seems to have a less than desirable track record.
I have come to the conclusion that this guy has taken me for a bit of ride and overcharging me for the service (which I confirmed with another reputable person in town asking me to quote the same work), and he also didn't necessarily honour his warranty after charging me another
I ended up putting a shop vac on the end of the intake pipe (disconnected) and blew some hot air through the tube from the outside to melt any ice or snow inside for about 10 min and made sure there was no obstructions. I reinstalled the intake on the furnace and the furnace seems to be running fine right now.
I know these Armstrong furnaces are not the most reliable, but I would like to get an opinion to see if there is anything abnormal about the flame that would indicate a cracked heat exchanger. There looks to be a bit of rollout during the initial ignition, but beyond that, to my untrained eye, it flames seem to be fairly concentrated through the openings and not like the examples of rollout I have seen online. Here is a video of the startup sequence of the burners.
Any thoughts?
Best Answer
First off I did not see anything in the video to make me think there was a cracked heat exchanger. The heat exchanger may be cracked but the video does not indicate so. It seems that removing the inlet pipe fixed the problem? The furnace installation instructions has vent tables showing what size pipe can be used for various lengths and amount of elbows. For instance a 90,000 btu furnace can have a maximum of 70’ of pipe and 4 elbows with 3” pipe but only 20’ of pipe and 4 elbows with 2” pipe. And this is combined for both pipes, not for each pipe. So adding the second pipe may have pushed you over the limit. This furnace comes with a restriction plate that must be installed if using only 1 vent but must be removed if using 2 vents. Was it removed? And in my experience these tables are often over generous. I have pushed the limits of the tables and have had venting problems. I had to either increase pipe size or reduce the amount of elbows or both.