Jt Some questions please. What is your location? What size home living area? What size furnace and eff are you replacing? What size AC are you replacing? I would like to know the exact mdl number evap coil for each quote. What thermostat is proposed for the Carrier quote? That is a big difference between the 96% eff Carrier furnace and the 80% eff Trane furnace-both 60 K input. That would be about 56 KBTUs output on the Carrier and about 48 KBTUs on the Trane. Not insignificant. I don't care for some shortcuts that homeowners make particularly on reusing linesets and using existing thermostats that shortchange a nice furnace's operational capability. Post back with the info requested. IMO

I'm replacing my ADP coil after two years of operation. I have a small leak in one of the capillary tubes. When I spoke with a Trane authorized dealer I was informed of two things. First the ADP coil does not carry the same warranty as Trane 1-5yrs in my case vs. 5-10 for trane. Second, even though ADP is going to replace the coil they will not warranty it beyond the date of the original start-up. ADP's clock starts running 1yr after manufacturing. They don't keep records of when they were sold or who they sold them to. This is probably not the case it's their customer service center passing this along. So as I would see it if your Heat and AC guy is pairing an ADP coil with your AC it's about cost. Here in Ga many companies working for builders rig these combos to save the builder money and to keep a job with them. Save yourself the headache and go with all trane parts because you aren't going to get the warranty with ADP. Most importantly our service men are receiving calls on these all the time. ADP builds them to order now so they don't have as much standing inventory as they once did, but consider this. They build a coil in the hay-day of building and it sits on a shelf for 6 mos. The builder has a system installed around that same time but doesn't sell the house and 18 mos later the bank owns it. Someone comes along buys the house from the bank and has the system turned on and the coil is already out its 1yr warranty. The Trane furnace is still in warranty but the coil is not. Just a thought.

What do you mean by "...moisture creeping down the walls..."? I really don't see how you can have "too many returns". Most people could use more. One in each room would be ideal, but is expensive so not often done anymore.. I am in your area. A couple of years ago I got estimates for re-doing a 2000 sq ft home with good equipment and all new ducts. The costs were $12-13k. If you are getting new ducts then 15k would not seem unreasonable. 3200 is a lot of house. If your ducts are outside of your house envelope, your moisture problems very likely come due to pressure differentials induced by the AC system. By outside, I mean in the vented attic or crawlspace. What happens is that leaky supply ducts blow air out and at the same time, in other places, moist air is drawn in to replace it. Either that or leaky returns suck air in and it has to be blown out through leaks elsewhere. The wet closets might be near the places where air is being sucked in and hitting cool surfaces causing condensation. Air often leaks in around poorly sealed "vents" and causes condensation too. Your closed-off ducts could have aggravated that problem. Note that "no leaks" might be a relative thing. The investigator might not have found any big leaks, but a typical residential HVAC duct system that age might be losing 20% of its air. Note that the insulation that you have might be great, but that does not speak to air sealing. You can have great insulation and still have a leaky house. Both duct and house envelope leakage can be determined by a blower door test. Another thing that causes high humidity is a system that has more cooling capacity than needed, They short-cycle rather than giving good, long runs that lower humidity better. At this time of year, you are in a period where demand for cooling is low and humidity becomes more of a challenge for even a right-sized system. As a stop-gap measure, you should consider buying one or two portable dehumidifiers. It is also important to monitor your relative humidity levels. Buy two or three electronic thermometer/hygrometers. Check them against each other for accuracy. Your humidity levels should be below 50%. (They should also be above 30%, but I think that you will rarely have to worry about that!) If you can lower your humidity with portable dehumidifiers, you won't save any electricity but you may be more comfortable at a higher temperature setting.

WHAT IS A HIGH LIMIT SWITCH? https://www.newcentralairconditioner.com/ The high limit switch in your gas furnace is a small part with two very important jobs. This switch plays a role in the normal operation of your furnace. Turning the fan motor on and off is the high limit switch’s main job. This is the role it plays in every cycle of your furnace’s normal operation. But that’s not the only thing that the high limit switch does. It’s also safety device that helps prevent your furnace from overheating. The high limit switch consists of a long temperature-sensing probe attached to a metal mounting plate. From the mounting plate, the switch is wired to the blower fan motor and to the gas valve. The switch is generally located just past the heat exchanger. This is so that it can detect the temperature of the supply air. In other words, the air that’s about to be blown into your home.