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Does this Sizing Make Sense?

Posted by cwhitla (My Page) on
Wed, Sep 7, 11 at 17:42

I am replacing a split HVAC system that handles the main floor + a 15x19 room and bathroom in the basement for a total of approximately 2000 square feet. The entry and family room are vaulted ceilings. The old unit was a 3 ton 19 year old Carrier system that had always seems at least adequate in performance when working properly. I typically shut the exhaust vents in the basement during the summer since it was usually cool enough without them open. The estimates I received were mostly all 3 ton replacements of various brands based on my satisfaction with the old unit. However, two companies did load assessments and the weird part is that one told me it should be a 2 ton and the other said it should be a 3.5 ton! I tend to think the 2 ton is grossly undersized and wonder if the 3.5 ton might be too large? Anyway, here's the suggested unit based on the 3.5 ton load:
Trane XL16i 4 Ton 2 Stage, Trane XV-80 80K 4 Ton 2 stage variable speed 2 stage furnace.

Does this sound like a reasonable sizing and solution? The home is in the Atlanta area and windows are all single pane except for a french door to the deck. There is another 3 ton unit handling the upstairs but also 19 years old.
Thanks for any advice you can provide.

Follow-Up Postings:

RE: Does this Sizing Make Sense?


I don't like that sizing at all for heating and cooling.

Basement finished areas at or partially below grade normally have low heating and cooling loads depending on insulation properties.

Heating a main floor beneath a second floor is not as great either. Of course, you have vaulted ceilings in one area of the main floor.

I agree a two ton is probably too small but the idea of a 4 ton seems oversized.

Back up and thoroughly review carefully before making a decision.


RE: Does this Sizing Make Sense?

Thanks for your input but I wanted to clarify a bit more. The figures from their load assessment indicated:
96920 Btu Heating
44010 Btu Cooling

Based on that, the suggested 4 ton unit makes sense doesn't it? I mean there isn't a 3.5 ton unit so if a 3 ton AC is 36,000 Btu then it would be 8,000 Btu short and the 4 ton at 48,000 Btu would be the only choice although 4,000 Btu overkill.
Also, they mention "Balancing dampers will be added to all supply ducts at the supply plenum" which nobody else did. I am just reluctant to write them off if they really have their act together and the proposal has merit. Unfortunately, this is a hard decision for me to make without more experience and technical knowledge. By the way, both of the contractors that did the load assessments are Trane "Comfort Specialists". Does that have any real value or just a marketing gimmick?
Again, thanks for any input.

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