80% vs 90%+ furnaces

I am trying to decide btw an 80% or 90%+ furnace.
I am looking at Lennox, which has both, or a Trane, which only has the 90%+ in the varaible speed, 2 stage option I want.

This is going in my attic in NC.

One HVAC guy said not to do a condensing unit in the attic, another guy said it is OK if done right...but later added that yeah, it could freeze up.
So now I am a little worried about that.

Also, I am trying to figure out a cost savings that I might realize on the 80% vs. 90%+ unit. Any ideas on how to estimate that?

 

OK, so I'm more than a little worried about a condensing unit in the attic.
Are there extra measures you can take to prevent freezing? The contractor said they wrap the pipe in insulation. Anything else? I still have yet to see the layout of these things , so I don't know if/how you deal with it if the condensate does freeze.

 

Stay with the 80% for the attic, it just too much of a risk/gamble to do a 90% up there.

You could wrap pipes, and what not and hope nothing happens!

Your winters are not as harsh like ours in MN. and I'd spend the money on the Two stage variable speed like the Trane XV80 with the HOneywell IAQ t-stat.

 

In cold weather the furnace is going to be running a lot and it's unlikely there will be an opportunity for things to freeze up.

And a properly installed furnace and vent line isn't going to accumulate water --- it's going to be set up to drain water out as it accumulates.

The one issue might be the reservoir of a condensate pump, if one is used. Condensate pumps typically do accumulate water from the furnace and turn on periodically to pump it out. An attic furnace might well not need a condensate pump, draining water out of the house by gravity.


Personally I'd be inclined to accept guidance from a good installer on this issue.

 

thanks for the replies.
I guess I'd rather not have the risk with the condensing units, so I will go with the 80%.
The trane dealer said they did not have a 80% 2 stage variable speed unit. So the XV90 is not condensing?

 

You may want to have them check into that again!

Trane XV80

It is a condensing furnace. Anything over 90% is.

 

Oh, now I remember. I was only talking with my trane guy about doing a furnace to qualify for the tax credit. That's why we didn't even talk 80%.

 

True, you will lose out on the credit.