>Most of the new high efficient furnaces have dummy lights which give flash codes to help diagnose problems.> The two questions I would ask and research the daylights out of are as follows:
> 1. what is the average repair costs for this equipment
1a. And can I repair it myself reasonably quickly.
1b. Are the likely failures predictable and can I keep the required spare parts around?
>I found most often the problem was either the ignition module or dirty flame sensor/igniters. Natural gas burns clean but it will leave a whitish ash that acts like an insulator which inhibits the flame signal or ignition spark. Very seldom was it a mechanical problem like blower motor or combustion blower motor. With the condensing type furnaces there were sometimes an issue with blocked drain lines.
I spent most of my service call days working on brand new equipment, but once the initial problem was fixed I seldom had a call back. A learned college of mine always said,"There are so many safety devices on these new furnaces that they aren't safe anymore." It was more an expression of reliability than safety.> 2. what is the mean time between failures
This is one reason I have not rushed in. I have been observing friends who have high efficiency boilers and they have gone through several in ten years or so. The same friends recommended using a high efficiency hot water tank instead last time we talked.
My daughter's high efficiency gas furnace has been trouble-free after a minor initial issue.
As far as I know you can not buy low efficiency furnaces anymore, manufacturers don't make them.> It has come to my attention that these new high-efficiency furnaces have $500 control boards and they like to die every couple of years. Whereas my 40-year-old furnace has a thermal coupler, a quarter horse electric motor and a belt and I might have $200 in repairs every 20 years. To gain an extra 20% efficiency when one the majority of the gas bill is delivery charges and other BS it clearly doesn't make economic sense in my mind to spend way more money on a high-efficiency furnace only to have your wallet sucked dry in repairs.
If reliability and low initial cost is the goal, maybe you are right. I wonder if the codes allow low efficiency furnaces these days.