I have a Carrier Weathermaker gas unit in my basement. It appears to be high efficiency using large bore pvc for air in and exhaust. It has an evaporator coil mounted on top connected to a 21 year old Carrier compressor (38EB048350, couldn't locate info on it. Any help?). I don't know if the evaporator is as old as I can't see it. It may have been upgraded when the furnace was installed. Out of curiosity, what was a "high" efficiency seer rating 20 years ago?

The house is a Capital Hill town house built around 1912.

Put some gauges on the compressor and it had what seemed like a low discharge pressure, about 150. Suction was around 45 and suction temp about 50F. I expect that the unit is close to done if not over.

Learned a lot in the last few hours reading over the postings and thought I seek some specific input regarding efficiency and equipment selection.

I expect to stay here 20 years or more.

While I have the high eff natural gas furnace, I don't think the blower is VS. How much would a VS unit contribute to efficiency? Comfort?

I live in Washington DC? Is a heat pump an economical choice, considering I already have a HE furnace?

What about modding the blower? Are there retrofit kits for this kind of thing to convert to VS or do you have to buy an entire furnace (since this blower is part of the existing furnace)?

The ducting is at least as old as the AC and it is sheetmetal insulated with board (inside) through the crawl space. The radiator system has been replaced with forced air and the duct work serves double duty for forced hot air and cool air. The first floor comes up through the floor vents and the second down from the crawl space.

Electricity here runs me about 10 cents per kwh. They deregulated and now have complex bills itemizing production and distribution charges. I simply divided the dollars by the kwh's.

I'll search for opinions on Goodman and others but feel free to name drop. Thanks. What a resource!

Paul Krupa