re: A/c question re: 1986 trane condensing units

Ask to see the electricity bills.

I bet they are $600 in the summer.

We had the same issue when we moved into our house. Actually had an old AC/furnace inside, and a recent cheap Goodman unit outside. This unit was operating at 50% efficiency, which easily would have pushed the energy bills up to 300-400 a month. My guess was the kids of the elderly lady were trying to prop up the AC unit until she was out of the house.

Anyway, a new 5 ton Rheem unit with new furnace and new duct work for a 2800 sq ft house was about $12k. I was told about half of that was for duct work. That was in 2013 in BR.

Now our energy bill never breaks $100 a month, except for July and August usage. I expected the savings from the new unit to pay for themselves within 4-5 years. Plus you really have to factor in increased expenditures for the old units and the fact that they WILL go out in the middle of August.

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The outside unit, whatever that is called

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It is possible but I seriously doubt the compressors are the original in both of them (really either of them). If they are, it is a no brainer to replace the units and I generally think its a good idea to replace the inside portion of the AC as well, to make sure the evaporator and condenser sections are appropriate matched. If it has a newer gas furnace, that could stay.

I swear by Goodman.

ASHRAE says units have a lifespan of 12-15 years. Most of the time if any type of PM work has been done, those numbers go up. However, your units are OLD. With R-22 shooting up to about 25.00/lb, i would just bite the bullet and get new units with 407c refrigerant. Generally, a full replacement of condenser and AHU's run about 1400-1800 per ton. So you are 14,000-18,000 to replace bumper to bumper. Those units are probably super inefficient so your energy bills will be way higher than they could be.