We are buying a house that our inspector thought the a/c was not large enough for the size and location of the house. (3200 sq. ft. large south facing windows and 4 bedrooms upstairs) The a/c unit outside is a Trane XR11 md. 2TTR1036A1000AA (I understand this is a 3 ton unit) and the Furnace is an XR 90. We asked the seller at the inspectors advice to have a qualified HVAC contractor investigate. We then received a letter stating from the contractor that the XE1000 A/C installed in 2/2003 has been designed to meet the proper specifications for this home. Is the XR11 and XE1000 the same thing? We know for sure the condensor outside has XR11 on it. Any advice? The local Trane dealer I talked to said the rule of thumb is 600sq.ft. per ton.