Case in point, a few years ago when I was a new homeowner I converted to natural gas from oil and got three quotes from three highly rated companies. All three companies recommended the exact same boiler. A few months ago I started to research the outdoor reset functionality that allows it to change the water temperature based on the outdoor temp. Well, I discovered that the feature is basically useless for me because both of my zones are too small to generate the minimum number of BTUs at lower temperatures. So I have a (up to) 96% efficient boiler that will never be able to reach that efficiency. I either would have needed a smaller boiler and or a buffer tank to be able to work correctly.
In trying to fix it, I had multiple techs come out and none really fixed the issue. These are basically some notes on the experience: - First tech stayed for 6 hours. Cleaned the system, replaced a high pressure switched, and readjusted the PVC in and out takes. The pressure switch alone costed over $500 dollars. He did the PVC for free. The problem persisted after he left. - First tech sent a second guy out the next day. This guy comes in and within 10 minutes recommended replacing my Nest with their "preferred" smart thermostat for a cost of $500. He also wanted to redo my humidifiers water setup ($200), and redo the elbow joint in the condensation output of the furnace ($200). After he quoted me all of that I asked him to leave. I redid the condensation output myself ($15 in parts), and humidifier ($15 in parts). I looked up the high pressure switched they replaced, and was shocked to learn it only costs $150. - I wrote my first Yelp review ever because of this company. They contacted me a day after I posted my review asking me to take it down in exchange for a partial ($300) refund. I agreed. - I had two family friends who do HVAC come out afterwards to look at it. After seeing that it was a high efficiency unit they basically wouldn't touch it. They are older and basically said they never retrained for high-efficiency units. It was never needed because they have more work then they can handle with older units. All they were able to offer was to give me a good deal on replacing it with a less efficient unit if I wanted.
At the end of the day my issue was never fixed. Luckily we haven't had as cold of weather as that week, so the issue hasn't manifested again. If it happens again I honestly will cross my fingers and hope the next company that I use is more helpful then the previous.
If you Google your furnace model you may find you tube videos with similar issues or things to check.
Most techs I get from companies have been very poorly informed and almost hopeless at "debugging" any performance or functional problem. The operating model seems to simply be to replace parts in a pre-determined "likelihood of failure" model.
I don't blame the techs - I liked most of them but after casual conversation it seems clear that most of them don't get much training.
I guess my main complaint is that while I definitely want to "call a pro" my experience finding a good professional in HVAC (and plumbing for that matter) has not been particularly successful.
And don't get me started on part pricing - I am very happy to pay for knowledge (with high hourly technician costs) but more than once I have had easily purchasable OEM parts massively marked up by HVAC companies in what seems just like price gouging.