Air handler closet full of mold

[Luckywest]

dampered combustion vents?

you don't need the combustion air until the furnace runs...
but there is a lot of liability for anyone to tell you to close them off.
there is the possibility that you would use the furnace without
opening. I can't imagine any hvac company recommending this.

you have to seal the top of the closet.
not gobs of mastic & by no means expanding foam.
with the hot attic air meeting the cool/cold coil housing &
start of the supply plenum mold will grow.

the attic insulation can be moved aside, the top of the
closet sealed, and insulation swept back into place.
shame that they blew the insulation so quickly...
and is it cellulose? ugh...dust making stuff.
missed the perfect opportunity to air seal & mastic
seal ductwork.
makes it a real pita for anyone to do the necessary work,
which sometimes is the point.

I'd like to see the top of the closet if you have one more
picture in you...
would there be room to wrap some R-6 or R-8 duct wrap around
the sides & rear of the coil & extend the wrap onto the
supply plenum?

Thanks again for all the help here! To be clear, no HVAC tech recommended sealing up the vents, we just wondered if it could be done as a temporary solution to the heat in the closet until we can get them out here again (we are about to leave all in the hands of housesitters for several weeks).

One of my pictures (this website turns it sideways, sorry) shows how close to the coil housing the nearest combustion vent is, and that is the one you can feel heat radiating from (the one that hangs lower in the closet, almost to the floor, doesn't feel so warm). Would extending that upper vent help, to get it from breathing hot air onto the coils/plenum? You can also see in the other pic that the whole shebang is close to the walls on both sides, and apparently mounted against the back wall (which we can only hope was properly insulated, as no way to see back there. There's about the space of man's hand between the drywall sides of the closet and the unit/plenum.

[energy_rater_La]

Am I missing something here?
to me it seems like one vent goes to the return?
granted Austin is miles ahead of La. in terms of energy
efficiency...but if I put an open vent from attic into return air...
I'd be introducing dirty hot humidity laden air...past the filter
& into the return. it would be like a return air leak...??
Shophound...your thoughts?

I've never added combustion air in this manner.
to the top of the closet for the gas burning furnace...
but not to the return below...
in my area, the one combustion vent would be added..
with a bug screen on the attic side.
but codes & code enforcement changes from state to state.
(town to town!)

in addition to the proper air tight insulated top of the
ceiling (with venting sealed into cuts)
I'd wrap the coil & as much of the plenum as possible
with R-8 duct wrap & seal it. at seams, top and bottom or wrap.

best of luck.

[Luckywest]

Thanks Louisiana. My pictures must not show that the second vent does not extend thru the floor of the closet to the return air space--it just hangs down about four feet in the closet from the ceiling (and doesn't feel like it's emanating as much heat). The second shorter vent, zip tied to it, extends only about two feet into the closet and breathes hot air right next to the coil. Our old unit didn't have tubes hanging down for combustion at all. It relied on the louvered door vents for air. I have no idea whether either one has a bug screen on the attic side, as that's a blown-in insulation no-man's land up there now! But I'm not clear AT ALL why there are two tubes. ??? Any ideas, anyone?

[Shophound]

Your furnace installation configuration in a closet of a house is a very common older house method of install in Texas. The two tubes that come down from the attic are to provide combustion air for the furnace now that the closet louvers are sealed. One extends lower than the other as code states so if one is blocked for whatever reason the other can still provide air (unless it also gets blocked). Neither of these tubes connect to the return air path for the furnace. Or at least neither one should.

[Luckywest]

Thanks Shophound. So code probably dictates the "backup" vent tube. All in all, the energy savings on this pricey new system aren't enough to make up for the problems occurring in that closet due to their jack-leg installation or lack of understanding of simplest formulas of heat + cold + moisture. We appreciate everyone's explanations here, it's made it much easier to talk to them about what's needed and not sound like pure idiots.