I live in the Philadelphia, PA area. My outdoor design temperatures are: Summer, 90; Winter, 14. Your area: Summer, 81; Winter, 36 with lesser humidity. My house is 2500 sq ft with good to very good construction. My indoor temps are: Summer, 76; Winter 66. The house requires 60,000 BTUs for heating; 3-1/2 tons for cooling. I could heat my house with your furnace 90 - 95% of the time. Of course, you can't just divide my figures in half to get yours, but this is why a heat calc is absolutely necessary, and is most essential for cooling comfort as you need to control temperature and humidity. I'd be curious what your present furnace is like (model number and size, age, etc.), and how it works for you (frequent short cycles vs. medium to long cycles). v

Thanks very much for your reply. The upstairs is 1100 sq ft. The main level is the same, as is the basement. The upstairs furnace is 50 BTU. The heating is natural gas. There is ductwork in the basement that supplies the main floor. The basement is unfinished currently. That may change. There are six vents upstairs with one return in the hall area. The return is 12x24. There are eight vents downstairs with one return in the hall area. The return is 12x24. I was told that the unit upstairs had a leak/crack in the compressor that could possibly leak carbon monoxide. There are marks on the outside of the unit that looks like burn marks. The heating unit performed fine the last time we used it before we found out about the burn marks. It is about 25 years old and about 8 SEER. The cooling unit seems to run almost all of the time in the summer. The downstairs unit also performs ok but needs a serious duct cleaning due to water from a pipe bursting in the kitchen getting into some of the ducts. We haven't used it in quite a while. The house has humidity problems sometimes (window condensation and my indoor hygrometer can get near 80% in the summer but is around 50% in the winter) and we would like a system that can take care of that and be more efficient. The upstairs unit seems to run all of the time in the summer. The stat is usually set around 75. I was told that 16 SEER two-stage would fit the bill. Other ac companies told me I needed nothing more than the typical 13 SEER. Some family members have asthma and I also want something that will help with that. How can I tell if my ductwork really needs to be enlarged? Thanks much for your input

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.

If you must turn to strangers on the net because you dis-trust people you hire,you have a much larger problem than water in your ducts.