If your current systems maintain temp during extreme cold weather, you can eliminate the Carrier guy. As there's no need to oversize the equipment.

New 60K 96% is 57.6K and the 80K is 76.8K
Both being a tad bit bigger than the original equipment.

The only reason to upsize the one system, is if it doesn't maintain temp and you have adequate ducting for the increase. Otherwise, its a very bad move.

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80/60 is the logical choice without doing a load calculation. Which should be done to properly size the equipment. Otherwise, you're relying on the previous guy to have sized the equipment properly. Who knows if the guy did a load calculation? If the units are original from 1962, I'd request a load calc. (Manual J).

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Did the Amana guy give you any reason for choosing to go smaller on the one system?

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Do you have a blue print for your house? If so, e-mail it to me.

quote:

Originally posted by Excam_Man:
If your current systems maintain temp during extreme cold weather, you can eliminate the Carrier guy. As there's no need to oversize the equipment.

New 60K 96% is 57.6K and the 80K is 76.8K
Both being a tad bit bigger than the original equipment.

The only reason to upsize the one system, is if it doesn't maintain temp and you have adequate ducting for the increase. Otherwise, its a very bad move.

My current system seems to keep up I guess. It's a little chilly in the house on very cold days, but I think we were hesitant to run it hard as we knew the house was leaky and the furnace was inefficient. First year here, not sure what it would cost (had hydronic heat at the old house).

Also, -- just a thought -- would the slight increase in BTU (capability) be ok, since the two stage would allow it to operate somewhere lower normally? Of course, a load calc will need to be done to verify. But conceptually, that seems sound.

quote:

Originally posted by Excam_Man:
80/60 is the logical choice without doing a load calculation. Which should be done to properly size the equipment. Otherwise, you're relying on the previous guy to have sized the equipment properly. Who knows if the guy did a load calculation? If the units are original from 1962, I'd request a load calc. (Manual J).

I think the existing systems were early 1990s.

quote:

Originally posted by Excam_Man:
Did the Amana guy give you any reason for choosing to go smaller on the one system?

He didn't give a reason. But he was the only guy to measure windows, so maybe he did a load calc. Or maybe he was interested in making sure his exhaust was small enough to go up and out the existing flue? (uneducated conjecture on my part)

While he did measure the windows, he may be underestimating due to the weird design of the house --vaulted ceilings without an attic for thick insulation, leaky bug eye light cans EVERYWHERE, and billet aluminum window frames all over the many many huge windows. This house should be in California, not western PA.

quote:

Originally posted by Excam_Man:
Do you have a blue print for your house? If so, e-mail it to me.

I have a paper roll blue print. Maybe I can photograph it well enough. I'll try.

quote:

Originally posted by r0gue:

Also, -- just a thought -- would the slight increase in BTU (capability) be ok, since the two stage would allow it to operate somewhere lower normally? Of course, a load calc will need to be done to verify. But conceptually, that seems sound.

He didn't give a reason. But he was the only guy to measure windows, so maybe he did a load calc.

The slight increase (4,600-5,800 Btu/hr.) requires less than 100 CFM at the proper temperature rise to be in spec. It shouldn't be a problem, unless the ducting is already to small. And like you say with two-stage equipment, it'll be running on low fire most of the time.

You can only get so close when the offered sizes are 40K, 60K, 80K, 100K and 120K at 90%, 92%, 95%, 96% efficiency. Unless you go with a true modulating furnace. A smidge bigger is better than too small to maintain temperature of the space.

Only reason to measure the windows is to do a load calc. or to estimate cost for their replacement.