Why guess on the size? Dealer should perform a load calculation!

How do you heat home?

You are replacing a HP system?

I prefer Trane or sister company AmStd over Lennox but that's my bias.

$8700 for the XP17 4 ton is not a bad price for LI, NY but I would want to know more details such as air handler Mdl number, size heat strip, and thermostat. Anything on new refrigerant lineset? Should be if you are downsizing. What about filter cabinet and thermostat?

IMO

" the salesman seemed to think that my original system was too big --is this possible? "

Have there been improvements in air sealing windows or insulation since the old system was installed? If so, then sure thing. Is the old system operating, nominally? If so, what is it doing on the most hot, humid days? If it is running constantly or nearly constantly on those days, the system is right-size. If it is spending significant time off, it is oversized.

Is the duct work for the upstairs AC in the attic? If yes, has a contractor evaluated for size, leaks, and layout?

The proper way to size an AC is to do a load calculation. I would think a 3 or 3.5 ton condenser would be sufficient for upper floor of 2000 sq. feet. The 5 ton was over sized, and my suspicions is the duct work was probably too small to handle the air flow.

Thanks for your responses:
1) it includes an HC10 filter cabinet and the Icomfort thermostat. I have gas heat, so I do not expect to be using the unit for heating much (just as a backup?) the handler is the CBX32MV48. We don't have any hyperallegenic children, so I'm not sure why I want to go the route of an additional (expensive) filter cabinet.
2) I also priced out the Lennox system--just AC--using a 5 ton system (XC17-60) and CBX32MV-068 handler). After rebates, it comes to about $8200 for the system.
3) To complicate matters, another salesman came in and quoted a Tempstar TX5600 with an FVM4+ handler for around 7600. I'm under the impression that Tempstar, while pretty good and quiet, is not as good as Lennox--does that make sense?
4) Re home improvements: while we redid our house and put in better windows, the contractor did not install an extraordinary amount of insulation or seal properly (ie, we had someone come in to evaluate). As a result, based on ionized's comments, i'll stick with the 5 ton unit. The ac doesn't cycle constantly--it will turn on, cool for an hour or two and then shut off.

I would recommend a load calculation. By a company or yourself. Just because your old system would runn for a few hours then shut off, doesn't mean it's not oversized. There could be a problem with it. After the house is cooled, I can't imagine a system running for a few hours. Maybe 15 minutes or so.

over40 , "I can't imagine a system running for a few hours. Maybe 15 minutes or so. "

I think most techs can agree you want at least 25-60 minute run times on cooling mode depending on ambient temp and RH levels in the home. It could also run continuous maintaining the set temp if 100F+ temp outside and the unit is sized correctly. If the system runs for 15 minutes or less its typically a sign of being over-sized but not always.

This post was edited by mrjasondude on Fri, Jul 25, 14 at 9:05