I had a new furnace installed last fall, and it turns out they didn't
set the fan to the right level for my A/C so it was blowing the
condensed water up into the ducts in the ceiling which was subsequently
raining down into my basement. In trying to find the source of the
problem, I had to remove some of the duct metal immediately downstream
(right furnace term?) of the furnace and immediately upstream of the
A/C coil unit.

The guys that installed the furnace used the funky three-fold metal
joints on all sides but then sealed it all up with what *looks* like
plain old silicone goo. The tub & tile type.

Now I asked at Home Depot and the one guy sounded very certain that
that wasn't the stuff - that I needed some other type of
construction-grade stuff. Said, "Oh no, you're dealing with *heat* and
so you need this stuff." Had a 700 in the name. PL700 maybe? It was
cheaper so I figured he wasn't trying to put one over on me. The tube
he pointed to had no temperature rating on it, and while it looked like
it would do the job moisture-wise, I didn't like the sounds of the
descriptions; it implied it was going to be hard to get off if I ever
needed it off.

So I bought the silicone anyways. Says it's rated to 400F which I
seriously hope my vents aren't hitting.

Anyone know if this is the right stuff? Or if there's anything better?

Thanks.

J

Jamie wrote:
I had a new furnace installed last fall, and it turns out they didn't
set the fan to the right level for my A/C so it was blowing the
condensed water up into the ducts in the ceiling which was subsequently
raining down into my basement. In trying to find the source of the
problem, I had to remove some of the duct metal immediately downstream
(right furnace term?) of the furnace and immediately upstream of the
A/C coil unit.

The guys that installed the furnace used the funky three-fold metal
joints on all sides but then sealed it all up with what *looks* like
plain old silicone goo. The tub & tile type.

Now I asked at Home Depot and the one guy sounded very certain that
that wasn't the stuff - that I needed some other type of
construction-grade stuff. Said, "Oh no, you're dealing with *heat* and
so you need this stuff." Had a 700 in the name. PL700 maybe? It was
cheaper so I figured he wasn't trying to put one over on me. The tube
he pointed to had no temperature rating on it, and while it looked like
it would do the job moisture-wise, I didn't like the sounds of the
descriptions; it implied it was going to be hard to get off if I ever
needed it off.

So I bought the silicone anyways. Says it's rated to 400F which I
seriously hope my vents aren't hitting.

Anyone know if this is the right stuff? Or if there's anything better?

Thanks.

J


Rest easy. The max plenum temp won't be over ~140F.
The silicone may off-gas for a week or so but after
that it's inert.

Speedy Jim wrote:
Jamie wrote:
I had a new furnace installed last fall, and it turns out they didn't
set the fan to the right level for my A/C so it was blowing the
condensed water up into the ducts in the ceiling which was subsequently
raining down into my basement. In trying to find the source of the
problem, I had to remove some of the duct metal immediately downstream
(right furnace term?) of the furnace and immediately upstream of the
A/C coil unit.

The guys that installed the furnace used the funky three-fold metal
joints on all sides but then sealed it all up with what *looks* like
plain old silicone goo. The tub & tile type.

Now I asked at Home Depot and the one guy sounded very certain that
that wasn't the stuff - that I needed some other type of
construction-grade stuff. Said, "Oh no, you're dealing with *heat* and
so you need this stuff." Had a 700 in the name. PL700 maybe? It was
cheaper so I figured he wasn't trying to put one over on me. The tube
he pointed to had no temperature rating on it, and while it looked like
it would do the job moisture-wise, I didn't like the sounds of the
descriptions; it implied it was going to be hard to get off if I ever
needed it off.

So I bought the silicone anyways. Says it's rated to 400F which I
seriously hope my vents aren't hitting.

Anyone know if this is the right stuff? Or if there's anything better?

Thanks.

J


Rest easy. The max plenum temp won't be over ~140F.
The silicone may off-gas for a week or so but after
that it's inert.

Hey, that's great news. I'll finish that up this weekend then. Thank
you!

J