80% 2 stage or 90% single stage

[dizzy46]

i am puting a 500sq addition on my house, i am getting a trane 40,000 btu furance for the addition .trane dosent make a 2 stage 90% 40,000 btu. so it is eather a 2 stage 80% or 90% single stage. can i get the pros and cons on the 2 choices.

[gary_g]

The 2 stage 80% should provide more comfort.

The single stage 90% should provide a 10% reduction in the heating portion of your gas bill compared to an 80% AFUE.

Good luck.

[dizzy46]

so its a toss of a coin ? 6 of one half doz of the other

[phbsales]

I would get the 2 stage 80%.

Most of the time, it's going to operate in 1st stage heating, since it's only trying to heat 500sq. ft.

Hard to calculate the savings, but if it operates most of the time in first stage, you're only going to use 20,000 btu's input, versus the full 40,000 of the 90% single stage.

[sktn77a]

Did you get a heat load calculation done on the new addition? 3.5 tons of heating sounds quite a lot for 500sq ft of new construction. A 2 stage furnace or smaller heat pump sounds like the way to go.