What is max service temperature of GE Silicone II sealant caulking?

[hrhofmann]

Have you called GE? Look on their web site or look on the tube of silicone, there is usually some number to call.

[dpb]

Sum Guy wrote: ...

As you've been told multiple times, go to the GE web site and look up the technical product data sheet for the specific material of interest.

If it isn't listed as suitable for the application, I'm sure GE will have a high temperature product that would be.

You're really not trying here...

--

[Evan]

It is quite clear that you are one of the nit-wit engineer type homeowners that gets hung up on specs and shit that no one in real life gives a shit about...

The only part of your "furnace" that needs to be air tight in the manner in which you speak of is the portion where the plenum enters and the heat exchanger is located...

You NEED NOT seal the rest of the furnace air tight as only the plenum (where the circulation fan is) and heat exchanger which are part of the duct work need to be sealed...

Again, if your furnace is that far gone that air comes out of it "all over the place" then it has other issues...

If you seal it up so tightly like you are seeking to do, it will no longer be able to draft air for combustion and will cease working...

As far as the "the main distribution [trunk] and collection [return air] plenums or manifolds, air-filter enclosure, where those structures tie into the furnace" that is all, umm what do you call it, DUCT WORK...

Mastic is used by home energy auditors to seal up leaky seams in existing duct work to improve air flow (pressure) in the duct work and reduce the losses of conditioned air escaping the ducts through other than the intended air registers...

Apparently you have not the first clue of what you are doing, nor what is actually important here and seem fixated on performing a totally unneeded and misguided repair to make your furnace "look" better...

If you have any further need for the specs on how whatever GE Silicone II product or whatever will perform, call GE and ask for it if you can not locate such information on the internet...

~~ Evan

[Evan]

ROFL...

I guess that you don't have a central AC unit anywhere in that duct work at all... Those need to be opened up at least annually to have the cooling coil in the plenum duct vacuumed and washed clean...

But hey, you sound like one of those guys who thinks that as long as you keep changing the filters every so often you are getting all of the dirty and crap out of your duct work...

Lol...

~~ Evan

[Sum Guy]

Evan unnecessarily full-quoted:

It's usually the case that "specs and shit" are some-what important when it comes to how things operate, and for how long, and for how well.

Any box, duct or chamber that generates or experiences a negative or positive pressure should be air tight.

bla bla bla.

Any box, duct or chamber that generates or experiences a negative or positive pressure should be air tight.

The furnace room is supplied with a dedicated out-door air supply duct. The return air ducting, plenum and fan chamber should not be able to draw air from this combustion supply duct, because if it does then it means a negative pressure is being created in the furnace room by the furnace fan, and this negative pressure must relieve itself by drawing air not only from the combustion supply duct but also the combustion flue or stack. In my case, the flue stack is not a sealed system with respect to the furnace and the furnace room, so a negative pressure in the furnace room will lead to air being drawn down from the flue (and the combustion air supply duct) into the furnace room and into the leaks on the return-air side of the fan. Naturally, any reverse air flow in the flue is not a good thing.

We all agree that sealing holes where air is leaking into or leaking out-of makes the system more efficient, and even more safe to operate.

I just want to use a silicone-based caulk, and you and a few others are going ape-shit over this mastic, even though I've said that the mastic is too cumbersome to apply in small or tight spaces, and I don't know if it dries hard or flexible (I would want flexible).

I never said this was about appearance.

[Twayne]

Read the product labels and don't forget about expansion/contraction of the metalwork. Personally I'd use the heat-resistant tape made for just such things.

HTH,

Twayne`

[zek]

400 F is normal and Hi temp 500 F

[chaniarts]

what did GE say when you called the 800 number that's on every tube?

[cwoliver148]

[cwoliver148]

THE MAX TEMP IS 400 DEGREES FARENHEIT. It does not matter where you put it. In a duct,as a gasket, or for your mother in-laws denture adhesive. 100% p ercent silicone is 100% silicone. There are additives (copper for one) that extend that range for use in extreme situations. If your furnace, in any o ther place except the burner (gas/heating oil) or heating element in an ele ctric system you should run away, if you can. I could blow a plethora of my vast knowledge of energy code, cleanroom requirements, and HVAC ICC code k nowledge, but the question at hand has been answered. Now go away and learn to research by your lonesome.

[Micky]

I don't know the temp of standard GE Silicone, the kind that comes in clear, white, and black, but if I were putting it right on the furnace, I'd use Hi-Temp silicone. Also called RTV Silicone. It comes only in some strange shade of red. My humidifier was dripping water on my flue "plenum" and that caused rust holes. I took it to be welded, and the pro had retired and only some whipper snapper was there. He tried his best but for every hole he patched, he burned another hole. He overlaid it with a heavy sheet of metal but that only fixed 3 of the 5 sides. So I used GE Hi-Temp silicone a few years ago and I haven't look closely lately but I think it's as good as new. I watched carefully the first week and the temp of the burner, which iirc makes spit boil, didn't affect the silicone at all. I also put it around where the burner meets the furnace, the ~18" circular plate is bolted to the furnance. It seemed that space was bigger than it should be and iirc hot air was coming out, air that should have been going up the chimney.

You should be shopping iirc at an auto parts store, not a hardware store. Also regular temp black is only available at auto parts stores.

It's probably a lot more expensive per gallon than mastic, so that's why people push mastic, but I only used 2 tubes, and I used a lot.

I don't think you need to seal around the air filter or the intake. Some of the air will sneak by unfiltered, but so what. Eventually it will all go through the filter. It doesn't have to go through every time. It's not like the filter catches every particle whenever the air goes through. Depending on how cold it is and how much the furnace runs, the air goes through maybe 20 times a day, so if it got fully filtered the first time, there would be nothing to do the next 19 times or the 20 times tomorrow.

[Micky]

Not that they're trying to save money, but that in the trade they're going to use mastic for installations, so they think about using it for repairs too. They also have an open gallon, so they don't have to go out and buy a gallon, 128 oz., for a 6 oz. job.

The silicone wouldn't work for new installations because it runs and drips.

[Jack Reed]

392 degrees Fahrenheit isn't really high-temp?

[Ed Pawlowski]

For making coffee, yes. For industrial processes, baking potato, searing a steak, not so much.

[Tiago50]

replying to Jack Reed, Tiago50 wrote: I know this is an old thread, but here is the data from the MSDS: This product contains methylpolysiloxanes whic h can generate formaldehyde at approximately 300 degrees Fahrenheit (150'C) and above, in atmosphe res which contain oxygen. Formaldehyde is a skin and respiratory sensitizer, eye and throat irrit ant, acute toxicant, and potential cancer hazard. A MSDS for formaldehyde is available from Mo mentive., Methanol released during curing.

You might want to look at using another type of sealant.

[zilagod]

max temp is 400F

[trader_4]

Another thing worth knowing is that the II version has an anti-microbial added, so it's not suitable for uses like an aquarium. I've seen people saying it killed fish. Happened on that when I was looking for something reasonably food safe. The "I" version doesn't have the additive.

[Evan needs a daddy]

replying to Evan, Evan needs a daddy wrote: Dude, You are a dick! Just admit you don't know the answer and politely bow out of the conversation. Talking about shit you may have heard one of your mom's sugar daddies talking about in passing isn't earning you any points with the folks who actually know what they are talking about. Just because you aren't mentally capable doesn't mean others are similarly deficient. Some of us actually made it through highschool and *gasp* into college where we *double gasp* learned stuff - ya know - like En-gen-eer-ing...

The max operating temp for GE II is 400F.

Stay out of the way and let the big boys work!

[Idea Factory]

Please behave like an adult now. Language. We are all learning from every comment. I have an application where I'd like to make an easy mold of something, so I can reproduce it by pouring molten lead or solder into the mold (mold made of something that begins as plastic (soft) and hardens to a rubbery consistency, but can take high heat of molten solder or lead. All of these products look like they might be good candidates and work (or not). I believe solder melting point is 360-370 deg F (180-190C) but can be as high as near 600 deg F, depends on the alloy/blend. So Mr Ransley, if you would be so kind as to please let me know the exact name of the product to which you are referring, as it looks like a typo in your comment. Did you mean to say "HVAC duct seal mastic ?" Does it have a number in the name or any other descriptor ? Please help + be more specific and please take a deep breath, + please do not resort to cavemanish name-calling, when you are frustrated. Oops, now I may have just done the same. Thank you, Greg PS I've noticed, people from Canada are really compassionate, polite, and kind-natured, like the better part of ourselves . And this was all meant with humility + respect to everyone.

[Idea Factory]

Idea solution : I'm reading that you need the tube for ease and ability of application. Is there a way to place the mastic into a calling tube and squirt it on/in ? Does the mastic have the right viscosity to be squeezed out of a calling tip ? If so, this mastic wud work for both use cases. Does mastic hold up to furnace temps ? 350 - 750 deg F -G