Air Conditioning - Please Help!! Deciding on Estimates

:confused: I currently do not have a/c and have been looking at installing it. My home is 1700 sq ft, full basement, is approx 60 yr old, and I live in DE; the oil furnace sits on a 3-4 in platform. I've had 4 estimates given to me; the 1st one (and only one) did a heat load (?), said I needed to put in duct board, (I currently have metal), replace the oil furnace with a lowboy model because it is too high and a coil will not fit on top of it-and because the return next to the furnace was not large enough--when I moved in 10 years ago the heat exchanger was cracked--due to the too small return ?--then put in the a/c. 2nd guy said to replace furnace, ducts, put in a/c. 3rd guy said to keep furnace, move it off the platform to accommodate the cooling coil, cut a vent in the return vent next to the furnace, put in a/c. 4th guy said ducts don't need to be replaced, if furnace works keep it but move it over, put in a/c. The first two estimates were to the tune of about 10 grand apiece...3rd was approx 9 grand and the last guy was about 4100 for a/c and new furnace. I don't know who to believe! Do all these things sound right? In reading some of the other postings, I think I should keep the metal ducts...Do I go with the cheap guy even thou he didn't to the heat load test?
All comments would be appreciated!! Also, great stuff in the postings!!

How many did a cooling load calculation? Without that they are guessing. If the furnace is over 15-20 years old, you might want to consider replacing it at the same time even if you can add A/C to the existing one. Here is a web site where for about $50 you can download & run your own Manual J heating & cooling load calculation. If nothing else, it helps to keep the honest people honest. http://www.hvaccomputer.com

Thanks Grady, I'll keep the website in mind. Only one person did a heat load calc. No cooling calcs... (not sure it they are the same thing) Furnace probably is 15 yrs old...(I've been there 10) I'll be keeping this in mind...

How many did a cooling load calculation? Without that they are guessing. If the furnace is over 15-20 years old, you might want to consider replacing it at the same time even if you can add A/C to the existing one. Here is a web site where for about $50 you can download & run your own Manual J heating & cooling load calculation. If nothing else, it helps to keep the honest people honest. http://www.hvaccomputer.com

oops, sorry, wrong thread.

Manufacturers and dealers want you to install the furnace, evaporator, and condenser at the same time. Of course, because they make more money that way. But ... they also match their furnace blowers and controls with the A/C evaporators, just like the evaporator is matched to the condenser.

For example my Trane furnace controller board has separate switch settings for cooling fan speed and heating fan speed. The contractor can adjust the fan speeds based on the pressure in your ducts and typical local weather so you get the conditioned air delivered as efficiently as practical.

Additionally the controls on the furnace know when you're cooling and when you're heating and ramp the fan up and down very gradually, and differently based on whether you are heating or cooling. This is a really nice feature because there are no sudden jarring starts or stops of the blower.

It's possible that your old furnace has these features, but if not, consider a new furnace. Replacing it later will probably cost more than doing it now.