Oh, I do have a question. Is a special thermostat needed with this GMVC8 variable speed two-stage gas furnace?

Or, can I use my existing Honeywell RTH230B programmable thermostat?

Your current thermostat is not compatible with a 2-stage furnace. You need to buy a thermostat which will control the furnace properly.

The parts warranties are limited. Make sure you understand what these limits mean. How long it the labor warranty? Is it being supplied by the contractor or will it be honored by any Goodman dealer?

An extended labor warranty wasn't offered, so just a 1-yr warranty from installer.

Thanks for info on thermostat. I remember reading that its preferred that stat do the thinking n not the furnace.

By the way, my decision to replace the entire a/c system is due in part to these factors:

1. Outside condenser broke down and it's 24 years old and uses R22 freon which is now being phased out in favor of R410A refrigerant. I didn't want to get a replacement R22 unit and I prefer to switch to R410A.

2. Evap coils are 24-years old and full of R22. Can't be cleaned because they have too many curves in the copper tubes, so they have to be replaced.

3. Existing lineset is full of R22 freon and the oils that go into the liquid. Many installers prefer to flush the existing lineset, but I got a lot of advise on this board to replace the lineset with a new one. This way you don't have to worry about the flush being done right.

At minimum, I wanted to replace the evap coils, lineset, and outside condenser.

Unfortunately, my existing gas furnace was installed upright in the attic and the evap coils are about 5 feet from the gas furnace. Even though the gas furnace works fine, I decided to get a variable speed high efficiency motor gas furnace to get the best possible SEER-15 with the new matched evap coils and new outside a/c unit.

So, I'm getting a complete new system with new ducts, new lineset, new gas furnace, new coils, and new a/c condenser.

If parts of my existing ductwork weren't original from the early 1950s and I wasn't using R22, I would have only replaced the broken outside condenser. It would only have cost me about $2000 to do this. I would have been happy with SEER-13.

Make sure that the old returns are well-sealed.

Thanks for tip on registers. I'm going to be up there in attic checking things out.

mastic seal of duct take offs on plenum,
plenum connections to equipment, return plenum
@ entry into house, air tight r/a chase (if you
have chase...ductboard or sheetrock)and
take off supply register & mastic seal gap
between supply box & sheetrock.
I use Hardcast brand 1402 mastic tape only.

use good media filter.

Thanks for the picture. I assume that's a supply register in the photo. My supply registers are not getting touched, so I'm going to have to do this on my own. The picture is worth a thousand words.

This reminds me. One of my two 12x24 return vents is at the bottom of my wall. The other 12x24 return vent is on the ceiling. Both are in the center of my house in the hallway that leads to all the bedrooms.

The return vent that's at the bottom of the wall had an inside 12x24 opening directly to the dirt in the crawl space. I suppose this was not good.

I recently put a piece of plywood to cover the hole inside this return vent. I used regular duct tape to seal it. Is this a good way to cover the opening to the crawl space?

My house was built in 1952 and I'm not sure why this return vent had a pathway to the crawl space.

OMG, a return that brings in air from under the house? I don't want to think about it.

Tape is not good. How did you attach the plywood, and what is it attached to? If wood, I would think some construction adhesive/sealer would be good.

ours is not to question why..it will drive us nuts.
the inside of this r/a chase is small?
I like to get inside the return plenum and
air seal the return, as otherwise dirt builds
up on the coil. Personally I'm not really
big..so I can get inside most returns.
I use ductboard & button cap nails to seal the
walls of the return.
measure inside of return & cut pieces
to fit. sometimes..I have to take the
return plenum (or duct) off in the attic
& lean in from the attic to finish the job.
hardcast brand 1402 mastic tape for all
seams.

the plywood 'floor' you put that in from
under the house..or from inside the return?

I'd oversize plywood & install it from
under the house. caulk where it will fit between
floor joists.
then from inside the return caulk it in place.

I usually finish off the ductboard-ed return
with ductboard on the floor of the return.
and mastic tape bottom piece to ductboard
walls.

wish I had a picture of one of my installs
to post...but sadly...

at the very minimum replace the duct tape
with caulk/liquid nail/construction adhesive.

duct tape is good for just about everything
except anything to do with hvac.

once you've finished with this return
go to the one in the ceiling & mastic seal
all the joints of the 2/x's. on the
attic side of this return you should move
back the insulation..and caulk bottom 2x
to attic floor.

I'm sure you'll notice a difference
with the open to the crawlspace closed.

Thanks for the advise. This return has a 12x24 opening and the inside is about the same size. The plywood sits on top of wire mesh that was already there...as if it was designed to be open. Was there a different thinking back in the 50s? Or bad install?

I'll get it fixed right.

At least it had mesh in it to keep raccoons out :-)