I am putting a thru-wall air conditioner into my apartment. I'm in Manhattan and went through the pain of getting Landmarks approval to do this. My contractor said he is going to be ready to do that part of the job soon so I called three different appliance places today. I got three different answers about BTUs and each of the salesmen was emphatic and defensive about his advice.

The first guy (Gringer & Sons) told me 16,000 and gave me a quote for a 15,800 Friedrich unit.

The second guy (Drimmers) told me 24,000 BTUs but for the location where it will be installed -- close to ceiling -- and the requirement of having it rear vented, I only have one option -- a 14,000 BTU Friedrich. He told me he has been selling air conditioners for 20 years. I thought 24,000 BTUs seemed excessive for the space.

The last guy (Yudin's -- I am getting all other appliances there) told me 12,000 BTUs. When I told him that sounded low, the conversation got very heated and he told me he would have to get back to him. I told him that I want to be able to compare the same models in order to compare quotes. He was very angry.

I need help. The unit is going in my dining room. The next room is an office, with french doors that will be open most of the time. If I find that the space does not get cool enough, I could put an A/C window unit into the office at a later time. I just don't know that it is necessary. The dining room, office and adjoining bathroom are about 400 sq. ft. Ceilings are 9'4". There is no natural light in the dining room (no windows) and very minimal natural light -- even in daylight I would need a light on to do anything -- in the office.

Any suggestions?