The original 3.5 ton, 10 SEER York air conditioner in my circa 1999 home needs to be replaced. Wasn't generating the right amount of cooling, low refrigerant pressure and leaky evaporator confirmed by local HVAC company. We also have an 80k BTU, 80% single speed York Diamond furnace that works fine.
We're in the Maryland suburbs of DC in a 2400 sq ft, 3 story end unit townhouse (basement level is 1/2 underground at front of the house, walk out in back). The supply ducting is split with one set going to the first and second floors and another going to the 3rd, with manual dampers. The AC has always seemed adequte, keeping the house comfortable even on the hottest days. The heating if anything seems too strong, the house very quickly comes up to temperature and it does seem to cycle more than the AC does. Only comfort complaint is that the basement floor stays pretty cool in the winter (there's a gas fireplace there we occasionally use, it actually heats the whole house pretty well if left on for a while), and that the 3rd floor (3 bedrooms) is a few degrees warmer than the rest in the summer. I have the thermostat drop a few degrees around 1 am to get an extra shot of cooling in the summer. Review of bills shows that we spend ~$450-500 per year each for heating and cooling. We'll be in the house a minimum of 5 years, probably 10, possibly longer.
I called in 5 companies to provide estimates. All seemingly legit local businesses - 2 big ones, 2 moderate (one of whom I've used occasionally over the years for repairs/maintenance), 1 small. One of the big ones is listed on this site's contractor map. None of the 5 did a Manual J. All of them examined the existing equipment and measured the return ducts at the air handler. One of them (the small one, the owner was the guy who came out) did a walkthrough of the entire house and looked at the supply and return vents. Everyone has quoted a 3.5 ton AC for replacement and ~80-90k BTU furnaces. I think I'm OK with this as the existing stuff seems to be working fine, but I'm very curious as to whether a lower output furnace might be suitable.
I'm still going back and forth with them to get more details and clarifications, just looking for some general advice now. Based on the estimates so far, there seems to be some economies of scale for doing the entire system vs. just the AC. So to some extent not doing the furnance now is gambling that it'll last a good while longer. If we do decide to do the furnace, just replacing it with a new one that's functionally the same adds ~40-50% to the cost of the AC replacement. Going with a more sophisticated type (variable speed, 2 stage, etc) adds another grand. In some way it doesn't seem "worth it" to just put in a new one that's the same as the old one, but on the other, going with a higher spec system nearly doubles the cost of just doing the AC.
Realize I haven't actually asked much in the way of questions so here are a few specifics:
- is it a big deal that no one's doing the manual J?
- typical life of a furnance like we have?
- is a variable speed furnance really that much nicer? How about one of the mid-grade 2 stage furnaces?
- Quotes are for Bryant, Lennox, and Trane. From what I gather the hardware is all basically the same quality so any would be fine. Any particular models of each that should be avoided, or represent a poor value? I think I saw somewhere on here that the basic Trane XB300 AC unit wasn't well regarded.