We have, I believe, a 2-ton Lennox AC/Heating roof-top unit. Lately, the unit was having trouble cooling the house, which is about 1,500 - 1,700 sq ft. We could set the thermostat to 68 degrees, and the house would only cool down to 80 degrees.

Yesterday, the unit stopped blowing cold air completely - only hot or warm air. What is this a symptom of? For a home this size, what is a typical unit in terms of tonnage we should be looking for. We had one contractor stop out today, and recommended a 4-ton unit at a cost of $10,000+. This seems very expensive.

Thanks!

We have, I believe, a 2-ton Lennox AC/Heating roof-top unit. Lately, the unit was having trouble cooling the house, which is about 1,500 - 1,700 sq ft. We could set the thermostat to 68 degrees, and the house would only cool down to 80 degrees.

Yesterday, the unit stopped blowing cold air completely - only hot or warm air. What is this a symptom of? For a home this size, what is a typical unit in terms of tonnage we should be looking for. We had one contractor stop out today, and recommended a 4-ton unit at a cost of $10,000+. This seems very expensive.

Thanks! why do you want to cool down to 68, unless you got $$$$$$$ to burn... that too cold, do you put it at 68 for heating too.when it run 7/24 the compressor would be death in about 6 years... you got to feed us more information to trouble shoot... jumping from 2 ton to 4 ton is not a very good idea, unless the 2 tonwas undersize, because the unit would come on/off too often.It would breakdown a lot more quick than a 3 ton

There is a possibility that you unit has a minor problem so I would call a small independent company to come out and give your unit a look over and see what they think is wrong with it.
I say Independent because so many of the large companies pay their men by ticket time, that mean the more that he can do for you the more he will get paid, some of them have 20 or so men working but only enough work for 10 to make a good living so the others have to fudge a bit to make a days pay.
Going to a four ton is too much unless you have lots of glass and no shade at all. An Air Conditioner is not only a cooler but it is a Humidifier and takes the moisture out of the house, dry air feels much cooler that moist air ( Have you ever been in a wet sauna at 110 degrees compared to a dry sauna at 140 degrees.. so if the unit does not run long enough it does not do it job of getting the moisture out of the building.

$10,000.00 sounds like a lot for a four ton unit but I have to be fair and say I have no idea what all is involved in completing your job, but I do know that before I did anything I would have at least four estimates.