My experience (as a homeowner, not an HVAC tech), having owned homes with newer (less than ten years old) but not necessarily modern/efficient units (furnace first home, boiler second), is that the quality of the installation and maintenance has as much or more to do with the life of the equipment than the brand or age. I'll skip the furnace nightmare, now onto a boiler which I'm replacing, undersized supply line, made up of about 5 separate, and leaking, sections, boiler resting directly on floor (thermal expansion and contraction issues), horrible plumbing job that made it impossible to bleed all air out of system, leaks in return causing too much make-up water, (encouraging corrosion) not enough valves, and no unions, making replacing parts an act of heroism, plumbing wrapped around unit making it impossible to access exchanger and clean soot (it's like a cage, did they think the unit would try to escape?), damper bent at installation and not functioning, no chimney cap in a windy area, et cetera, and most frustrating, a label on the side detailing service that never occurred (filter completely plugged, filter housing rusted shut, where I find filters aren't too bad when pulled annually, same with nozzle, a huge pile of soot in firebox, plugged exchanger, handfuls of soot in flue--I set smoke at #1 and get barely a handful of soot out each year)...
And the needed service in the last 6 years (burner is 10 years old), new damper, new supply line, new filter housing, new oil pump, new pressure reducing valve, countless air bleeders, cad cell (old one was probably shaken to death), and now a cracked boiler, and an experience of a noisy, rumbling, banging, short-cycling, stinking, leaking, undependable and dangerous boiler that heated the house in the summer better than it did in the winter.
I could go on with this rant, even include photos but, I think the point is made. There are plenty of bright, qualified techs, that are serious about quality, safety, a good owner experience, and a good relationship. This forum is full of them. It's just a bit of bad luck that none of the previous owners of my current or previous home ever got a visit from one, nor did I, when I called a few.
What I'm getting at is that I would encourage you to be much, much more concerned with who was doing the installation than what they are installing. There may not be that many parts but, there really is a lot to these systems. A few changes to the variables can completely change how well it works and how long it lasts, much more so for the modern, efficient units. As for me, I finally found a couple of guys that are good, one small independent, and one larger company that has a policy of hiring all it's techs at entry-level, so as to avoid them bringing bad habits from other companies. I wish I'd found them sooner, I would have had more peace in my home, more money in my pocket, less worries on my mind, and wouldn't have had to spend so many evenings reading about repair, maintenance, application and installation of these units, and wouldn't be installing one myself right now. C'est la vie. At least I have some people now, and will be able to hand these responsibilities over to someone better qualified to safeguard my family from hazards that have put my family at risk.
As for your old unit? It's easy to love old gear, it's all over-built, over-sized, made and installed when there was less to know, so it was easier to be good, and by someone from a time when pride in your work was a bit more common. That being said, I'm not trading my modern car for a '64 Dodge Dart!
Good luck.
Regards,
Mike O'
