I had my gas furnace "tuned up" today, and have some questions where input from the hivemind would be very helpful. Some background info: both the furnace and air conditioner are 18 years old, original to the house. The AC hasn't had any issues in the past 7 years, since I've owned the house. The furnace has needed repair twice in that time: the first time the sensor was too dirty to see the flame (learned my lesson there - won't pay for that again), and the second time the electric starter failed and needed to be replaced. No problems other than that. On to the questions from today:
1. The technician used a camera scope and blacklight to look for bacteria in the system. This was in the coil area, above the burners. There was definitely some growth in there. The company sells a UV light system that will keep the area clear of bacteria for around $1000. That area is warm and dark - of course bacteria want to grow there. The technician didn't recommend buying the UV light for an old system if I haven't been having any health problems (and I haven't). Points to him for honesty. I'm not buying a UV light for this system, but I'm curious if others have heard of them in HVAC systems? Useful new technology, or gimmicky sales opportunity? I've tried googling it, but everything I read seems to come from people selling the technology.
2. There's a very very small gas leak in the gas valve. It was only detectable by the technician's sensor when it was <1cm away from that specific corner of the valve. From what he said, it sounds like internal gaskets in the valve slowly fail over time, and it could have been like that for years. I used a different (worse) company for a tune up 2 years ago, and I'm pretty sure they didn't use a sensor to check for gas leaks. The quoted cost for replacement was around $800, which sounds insanely high for a component that appears to cost around $200 online. The technician suggested buying a combustible gas sensor for the basement where the furnace is located rather than spending $800 on an 18 year old system. The combustible gas sensor sounds like a good idea regardless of whether I get that component replaced. Should I live with the small leak or replace it? Is it possible to patch it without replacing the component (technician said no, but maybe there's a DIY coping solution)? If I do replace it, I'd definitely shop around for a better price.
3. Both the furnace and AC are 18 years old. Google suggests AC typically lasts 15 years and furnaces 20 years. Looking around the houses in the neighborhood, it looks like most people have replaced their AC. On the other hand, the furnace looks to be burning well (blue flame), the heat exchanger has no cracks, and the measured efficiency is 80%, which matches its rating. I live in the mid-Atlantic. It gets hot but not unbearable in the summer, and I'd be ok if the AC broke. It gets cold enough in winter though that I can't delay heater repairs without worrying about freezing pipes. With all that in mind, does it make sense to proactively replace the HVAC system? Or just do repairs on the furnace as required, and replace the whole thing when the AC eventually goes? I'm getting some quotes now, just to have the info.
4. I'll probably need a new HVAC system within the next 5 years. What kinds of questions should I be asking when I get quotes? What features are worth paying for, and what are just headaches to maintain? I'm thinking I want something mid-range, single stage, single blower speed. I use little enough energy (450 therms for heating total over last winter) that the extra expense of a fancier system probably doesn't make sense for me... right? I'm struggling to find good resources online that aren't trying to sell me something.