NEW CARRIER SYSTEM HELP NEEDED,,PLEASE

[GLEN1234]

Hello all. My current furnace, a 20 year old Carrier 58XSC100 (110,000 btu) just went on me (exchanger cracked). The local Carrier dealer who I have service the unit now recommends replacement with a Carrier Performance Series 59SP5A120 (120,000 btu). He says this one is 97.5% but the Carrier website has it as 96.5 efficient. He said that Carrier no longer makes the 110 only 120 btu model and a lower 100 btu model which, in his words, "may work too". He thinks the 120 would be better since about 5 years ago we added a 400 sq ft addition to the house. I can upgrade the unit to a two stage for about $ more. Anyway, I know pricing cant be discussed here but my questions are:

1. He said we'd be more, "comfortable" with the two stage..both units have an ECM blower. I have 4 zones, 2 upstairs and 2 down...True??

2. Since the new furnace is more efficient than the old do you think I should go with the 120 btu and not the 100?? House is situated facing south, 2 floors, about 3500 sq in Worcester, MA area.

3. Anything else I'm missing??

Thanks!!! I need to make this decision today.

[jtrammel]

The only way to know what sized you need is to perform a manual J load calculation. Otherwise its just a guess. I'd say 120k is way too big and 100k is too big.

[tiger man]

Ask him to install the carrier modulating furnace with infinity control, get a heat calc done with a reputable company