Considering Rheem modulating, however after reading posts online a little hesitant. Being a replacement read that return air is extremely important. Am replacing supply air duct size but contractor said return size of 8 x 14 sufficient.? Is return size as important say as in a two stage varible speed system (Trane ie)? Contractor sized unit as 100000 with 3.5 or 4 ton A/C. Also which size A/C unit would be best in reference to SEER? I think I understand SEER, but was trying to investigate EER for efficiency. Haven't found much info on brand specific eer ratings. Thanks for any info.

Rheem unit good

Return size very important

Size of unit it will depend upon where you live and the heat loss of the home.

The higher the SEER the cheaper it will operate in regards to utility usage.

Usually the higher the SEER the more the unit will cost to buy and install.

Considering Rheem modulating, however after reading posts online a little hesitant. Being a replacement read that return air is extremely important. Am replacing supply air duct size but contractor said return size of 8 x 14 sufficient. ??? Is return size as important say as in a two stage varible speed system (Trane ie)? Contractor sized unit as 100000 with 3.5 or 4 ton A/C. Also which size A/C unit would be best in reference to SEER? I think I understand SEER, but was trying to investigate EER for efficiency. Haven't found much info on brand specific eer ratings. Thanks for any info.
Rheem mod furnace are great. 8 x 14 return is no way even close to being enough for 3.5 or 4 tons cooling IT MUST BE UPGRADED. 8x14 may barely due a 1 ton cooling. And if that 8x14 connects to the side of the furnace. You will have a very dirty clogged filter quickly. If youask me get rid of that contractor or get a couple more bids.

HV1000 and Coolmen, Thanks for the information: I really appreciate your help and expertise. This site is awesome.:)