2-stage furnace has nothing to do with controlling humidity in the summer time. The variable speed blower in the furnace helps, if configured properly and used with the right controls, but otherwise, the furnace just provides the heat and airflow over the coil. I'd clarify what his premise is there. I prefer the XL15i over the XL16i, and I don't think the XL16i is worth $600 more. I really prefer to use Trane coils, but it looks like the ADP coil is needed to get the tax credit. I'd make sure it also carries a 10 year warranty.

Looks like he's quoting a smaller furnace with the 16 SEER setup?

I really think the 100k btu furnace is too much if you have a 3 ton system and live in a warm climate. Ask to see the heat loss figure (from Manual J) to support that. He's probably oversizing it to make the tax credit ratings (with the bigger blower in the 5 ton furnace). That would make sense why he didn't need such a big furnace in the 16 SEER setup. I would never oversize equipment to get the tax credit, in my opinion. Higher purchase and operating cost, and more prone to failure down the road. Also, it will likely need to move more air than the ducts can handle.

He claimed that he did NOT want to oversize the equipment. From what I have read in several forums I can't seem to find any fans of XL16i over XL15i. If they were the exact same price would you still prefer the XL15i? They did not do the Manual J and in fact the sales guy was a bit belittling saying it was a 'sales show' that he'd be glad to do if I wanted but there was no point if I did not have any renovations to extend the house. His point was that the original house had manual J and city inspection and it would be the same now.

As for the 2-stage furnace, he gave me a chart on COMFORT-R settings 'accomplished by running the fan at a slower speed during start-up'. For one minute airflow (cfm) at 50% fast coil heating/cooling then 7.5 minutes at 80% fast coil cooling 'dehumidify warm air heating' then 100% if necessary then taper down59% and off. "This provides improved dehumidification in colling startup." Premise: relative humidity lower - if 100% blower then blower will cut out sooner and relative humidity higher. I am sensitive to high humidity so if this makes a material difference I'm interested!

But could I save the $1k on 2-stage furnace and instead of comfort-r use Honeywell VisionPRO IAQ?

The Comfort-R feature is a factor of the variable speed blower which comes in Trane's 2-stage furnaces. So, the 2-stage furnace is needed for that. For high humidity areas, I prefer to use the Honeywell VisionPRO IAQ thermostat configured to control blower speed for dehumidification and not Comfort-R. That way, you get maximum airflow when you need it, and decreased humidity when you need it. When the airflow is lowered, efficiency is lowered, so I would prefer having the IAQ thermostat determine when dehumidification is needed. This is not a simple thermostat to setup and configure, so ask if they have any previous experience with it. If not, Comfort-R would be the next best thing in my mind (aside from the IAQ's ability to also overcool to dehumidify instead). I still prefer the XL15i. The 2-stage operation of the XL16i is not that impressive, with 1st stage being around 80% capacity to begin with (i.e., not much difference, and not that advantageous with regards to dehumidification). Did your present 3 ton, when fully functional, always keep you comfortable? Just because that's what you had beforehand doesn't mean that's the right size. It is understandable why many sales reps would shy away from them as to do them properly they take good time and a detailed study of your home.

As to the furnace size, I am still puzzled why with the 15 SEER setup he would quote a 100k btu furnace and with the 16 SEER only an 80k furnace. One size is best for your home, and the other is oversized. I'm willing to bet the 80k is correct, but a Manual J would determine that.

So when I get the Manual J what exactly will I be looking for that will answer that question or should I just post the results here? I have sent the sales rep (VP actually) 'my' questions :)

Your heat loss figure will be the btu's required to heat your home under design conditions. Your contractor should know how to interpret the results.

Let us know what kind of feedback you get from your dealer.

If the manual J is such 'sales show', then why does their quote list heat loss/heat gain calculation and separately, manual j if necessary?

I would be wary about sizing. Might want to do your own manual j (hvaccomputer.com) for $50 bucks.

V