Hello all,

Our residential building has to replace the air conditioner for the lobby and guess who's been asked to research it. The current A/C unit is attached to the ceiling in the basement and supplys air to the duct work leading to the lobby. A label on the unit indicates 2 tons. It's the original A/C unit in the building. We had some contractors come in to submit proposals. We've gotten a range of recommendations 2 tons to 15 tons. This seems like a wide range. The lobby is about 500 sqrft with 14 foot ceilings. North side of building, marble floor. Two sets of exit doors and walls consisting of wood paneling and wall paper. There are also about 10 ceiling lights of about 100 watts each.

My thinking is this. If a 2 ton unit was originally installed then the calculations for the cooling requirements were already done. The lobby hasn't changed. Can anyone give me a general idea of how to find out what size unit should be installed. 2 tons to 15 tons seems too large of a fluctuating range. I've contacted Carrier and they referred me to local dealers.

Thanks

CAH

It is hard to come by enough good data to make an accurate calculation. There are too many varibles. I would look at the old 2 ton unit. When newer was it adequate, or was it perpetually over worked and finally died an early death? If overworked, yeah, go with a bigger unit, but I doubt you need 7.5 times as big. Did it come on quickly create cold spots and kick off leaving the air clammy? Maybe try a 1 ton unit.

I'm really not sure when the problem happened. I'm at the tail end of this. A decision was made, which I agree with, to have a licensed engineer look at the situation. Thanks for your help. A good point about the system being over worked. I also read a report that a system too large can be a problem.