Using 60000 btu in place of a 80000??

[wantboost]

I heard someone talking how a installer replaced theirn20 year old 80000 btu with a 60000 2 stage . What do u guys think of this??

[tenletters]

Depends what it really needs.

I've replaced a brand new 100,000 btu unit with a 2 stage 60,000 btu unit because the sales guy from another company followed his spreadsheet and had no idea what he was doing.

If the heat load does in fact call for an 80,000 btu, they're SOL on cold days. That unit will never shut off and may possibly not keep up.

[Admin]

You also have to compare efficiency.  If the old 80,000 was mid efficiency at 80% the output would be around 64,000 BTU's, close to what a 98% 60,000 would give you.

Maybe the older windows were replaced.  Alot of times original furnaces are oversized to begin with.  Today's F280 designs reduce furnace size to increase run times and comfort.

[walker]

Mostly everything is grossly oversized,  even manual J calculations end up overshooting what's actually needed.  It gets even worse if the home has had extensive window and insulation and air sealing work done,  sometimes a new furnace is half the size of the old one and it'll still never hit the high stage.