The furnace stopped working at my Dad's place between November 13 and 14. It was working on the 13th. I was in, both days, cleaning in anticipation of putting up some cousins for a few days.
After fooling around with the thermostat and other things on Sunday, I called out a, let's say “FurnaceCo”, service technician. Diagnostic appointment confirmed for “between 0700 and 1100 on Monday”. That’s the 16th of November.
Met technician at approximately 0940. He spent a little while examining the furnace and then told me that the “heat exchanger” was cracked, showing me a photo on his phone of a slightly conical tube with a small crack. I asked him how he took that photo. The answer was, “With my phone.” I asked if he had some sort of tiny inspection camera on a rod, or something similar and he said, “No.” I asked how much it would take to repair, roughly. He was vague and said that it would be probably a few thousand dollars, that it probably wasn’t worth doing because that is most of the way to a new furnace. I asked him what, approximately, a new furnace might cost. He said, “I’m not allowed to give pricing.” Okay, fair enough, I know there are a lot of variables involved. He then went on to tell me that the “limit switch” had failed and that there “might” be a problem with the controller board or other components that are “heat sensitive”. That seems like a stretch, the PCB is by the air intake, below the burners, but okay. I asked about the cost of those items, and he suggested the switch might be a few hundred dollars. It’s possible that I misunderstood and that he meant the controller PCB, but he was waving at the limit switch when he stated the price.
The next part of our exchange was him asking me if I wanted to get a quote on a new furnace and that he could arrange for a sales guy to come see me right away. I agreed to that and he suggested 1100, which I also agreed to. Of course, there is a charge for the diagnostic call-out, which I was aware of. The tech told me several times that if I bought from FurnaceCo, the cost of the service call would be deducted from the cost of the new furnace. As if I, or your average customer, could tell the difference if it were marked up by $3100 or $3000.
I paid for the $99+GST service call, and he left, leaving me a copy of the invoice. Shortly after he left, he phoned to tell me that the sales guy, who I will call “Tré”, wasn’t able to come until 1600. I agreed to that.
I decided to dig a little more deeply into how furnaces work in general, and Carrier furnaces specifically. It turns out that the photo the technician showed me on his phone was of one of the burners, not the heat exchanger. Odd. He did not open up the housing where the heat exchangers sit.
There is an LED on the controller PCB that produces a flash code based on troubles it detects. I wish I had looked at that a little more carefully on the weekend. I found an installation manual for the specific model of furnace, with a circuit diagram. The flash code started out as 1-3, which translates as “limit or flame roll-out switch lockout”. I learned that the flame roll-out switch has to be manually reset. Looking at the circuit diagram, and tracing the wiring from the PCB, I figured out which one was the flame roll-out switch, and that there is only one in this furnace. I reset the switch and powered up the furnace. The flash code changed to 3-3, which translates as “limit or flame roll-out switch is open”. I had to wonder why the technician didn’t reset the flame roll-out switch. That’s when I started swearing to myself.
Double-checking the circuit diagram and the actual wiring, I confirmed the location of the limit switch and removed it. It is attached to a small PCB which is inserted into the body of the furnace where the heat exchanger lives. The switch itself is a sealed unit. It’s basically a temperature sensor which opens and breaks the circuit if the temperature gets too high. This one is rated for 170 degrees F. Part number is HH12ZB170. Cost is $12 USD online, plus shipping. Cost at Amre Supply is $31, available right now; substitute part number PHL506 rated at 170 degrees. I did not have a multimeter with me, but presumably the technician tested the switch, as he wrote on the invoice “limit switch open”. He also wrote, “error code 1+3” which suggests that he really didn’t reset the FRS. My swearing was considerably louder and more pointed at that point. I went to Amre Supply and purchased the part. See below for some further learnings about error codes and partial absolution for the technician.
Back at the house, I installed the limit switch, powered up the furnace, and watched as it ran through its start up routine and then fired up the burners. More swearing. More reading on the possible causes of overheating.
It turns out that one cause of overheating could be “inadequate combustion air supply”. I took a look at the filter, and realized that it hadn’t been changed since Dad passed away. He used washable electrostatic filters. I’m not sure if they are a good idea, or if they have a limited lifespan, but the filter was pretty dirty. I pulled it out and installed a second one that appeared to be clean and was sitting beside the entry door. After a bit of research, it seems like the “cons” of electrostatic filters might outweigh the “pros”.
It’s possible that there is a deeper issue with the furnace, but at this point, I think that’s unlikely. I haven’t found any suggestion that a cracked burner is a problem. You can buy replacement burners for about $25 USD each. I will keep a close eye on the furnace for a couple of weeks and check that the carbon monoxide detector is working properly. If there turns out to be a bigger issue, I will call Reliance for a quote and repent my evil ways.
Now I have to ask myself, “Do I consider this a lesson learned and eat the $100?” After all, had he reset the FRS, replaced the limit switch, and told me to get a new filter, I would have considered the $100 money well spent, even though I would have felt (even more) stupid about the filter. I’ll have to think on this a bit.
I learned later that error codes are not held through a power cycle, and that 3-3 changes to 1-3 after three minutes, so I have to give the technician the benefit of the doubt on the FRS question. There are still the significant matters of telling me that the “heat exchangers are cracked” when he did not look at the heat exchangers, showing me a picture of a burner with a crack and calling it a heat exchanger, not pulling or mentioning the filter, and not thinking it worthwhile to replace (or bypass as a test) the limit switch.
At 1530, I phoned FurnaceCo to cancel the sales call. After a short explanation from me and being placed on hold for a few minutes, I was informed that the sales call had been cancelled. At 1544 “Tré” called me to ask if I had cancelled the sales call. I told him that I had. He asked if I wanted to reschedule, and I told him, “Not at this time.” After a lengthy pause he said, “Okay, thanks.” Unfortunately, I have no way of knowing what was going through “Tré’s” mind during that pause.
I have to wonder whether the technician and “Tré” have a hustle going. Maybe this is how FurnaceCo increases business; there are also those, presumably profitable, potential sales of “protection plans” to consider. Maybe this is standard practice in the industry. It would be “gotten away with” for probably 999 of 1000 customers, and there would be plausible deniability for that 1 of 1000.
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