# Duct Seal



## bobelectric (Feb 24, 2007)

Brian mentioned this in another post. What is it? Plumbers putty? I know its a seasonal summer only type sealant.


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## BBQ (Nov 16, 2010)

> Duct Seal Compound
> Seals conduit openings against drafts, dust, moisture
> • Protects terminal boxes, pot heads and bushings from corrosive elements. • Deadens switch gear panel noise.
> • Dough-like compound is easily “thumbed” over holes and gaps.
> ...


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## bobelectric (Feb 24, 2007)

BBQ said:


> [
> 
> 
> 
> ...


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## BBQ (Nov 16, 2010)

bobelectric said:


> Not used outdoors.


Not sure what your point is.

The directions say not for outdoor use, traditionally it has been used outdoors.


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## papaotis (Jun 8, 2013)

i have seen it used outdoors many times and it seemsto hold up well, although i have also seen it somewhat dried out in these places(i'm sure it had been there a long time)


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## LightsOn81 (Jan 6, 2012)

I've always used it for conduit where either the ends of a run are in two different atmospheres, like a main feed coming into building underground from outside, or there's a potential for water to back up in the conduit like the machine gun target in my avi pic. The water table is so high, if it even drizzles where it's at, it's like Noah's Flood.


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## LightsOn81 (Jan 6, 2012)

I've also used it patch a leaky valve stem on my car :thumbup:


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## hardworkingstiff (Jan 22, 2007)

*Opinion?*

Can it be used to meet the requirements of 504.70?

In other words, is it listed for that?


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## brian john (Mar 11, 2007)

BBQ said:


> Not sure what your point is.
> 
> The directions say not for outdoor use, traditionally it has been used outdoors.


Traditionally? Like maybe 80-90% use is outdoors. Just saying my exierence.


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## denny3992 (Jul 12, 2010)

Guaranteed to dry out when applied to the top of a meterbase and then let water in and follow cable to the main breaker which in turn then freezes or rusts out the bottom of the can!


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## captkirk (Nov 21, 2007)

I never understood that either. The name alone should be a clue.....DUCT seal..... i roll with silicone for sealing stuff


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## Big John (May 23, 2010)

captkirk said:


> I never understood that either. The name alone should be a clue.....DUCT seal..... i roll with silicone for sealing stuff


 Pretty much exactly what I was gonna say. Looks crumby, doesn't really work. Not sure how we got into the habit of using it.


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## varmit (Apr 19, 2009)

Big John said:


> Pretty much exactly what I was gonna say. Looks crumby, doesn't really work. Not sure how we got into the habit of using it.


It was always cheap, available at any supply house, pliable and easy to work with. The old caulking compounds, sold years ago, were not much better when used outside. In those days there was not a Lowes or Home Depot on every corner either.

In answer to hardworkingstiff: Yes, "duct seal/ electrical putty" can be used as a sealing compound in Class 2 and 3 areas. In these areas the purpose is to block the travel of dust (Class 2) or lint (Class 3) and the seal is NORMALLY not required to be explosion proof. A "C" fitting packed with duct seal is a common Cl 1, div 2, sealing method.


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## BBQ (Nov 16, 2010)

captkirk said:


> The name alone should be a clue.....DUCT seal..... i roll with silicone for sealing stuff


For sealing a bell box connector or other such things silicone for sure.

For sealing an an electrical duct from air movement as required by 300.7



> *300.7 Raceways Exposed to Different Temperatures.
> (A) Sealing.* Where portions of a raceway or sleeve are
> known to be subjected to different temperatures, and where
> condensation is known to be a problem, as in cold storage
> ...


Duct seal makes better sense.


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## Jlarson (Jun 28, 2009)

Foam or dap 230 caulk. Duct seal sucks.


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## Semi-Ret Electrician (Nov 10, 2011)

BBQ said:


> For sealing a bell box connector or other such things silicone for sure.
> 
> For sealing an an electrical duct from air movement as required by 300.7
> 
> ...


• Not for use outdoors.
- Temperature Range: Adheres at -20 °F (-29 °C). Will not slump after 1 hr. at 350 °F (175 °C).

Not for use outdoors but OK down to -20F ?
NEC says:

*300.7 Raceways Exposed to Different Temperatures.
(A) Sealing.* Where portions of a raceway or sleeve are
known to be subjected to different temperatures, and where
condensation is known to be a problem, as in cold storage
areas of buildings or where passing from the interior to the
exterior of a building, the raceway or sleeve shall be filled
with an approved material to prevent the circulation of
warm air to a colder section of the raceway or sleeve.

Sounds like if the cold storage unit is indoors and runs between -20 and +350F it's OK:thumbup:

But don't use it outside in Honolulu!:no:


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## BBQ (Nov 16, 2010)

Jlarson said:


> Foam or dap 230 caulk. Duct seal sucks.


As long as the right person approves it. :laughing:



> 300.7 Raceways Exposed to Different Temperatures.
> (A) Sealing. Where portions of a raceway or sleeve are
> known to be subjected to different temperatures, and where
> condensation is known to be a problem, as in cold storage
> ...


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## captkirk (Nov 21, 2007)

Big John said:


> Pretty much exactly what I was gonna say. Looks crumby, doesn't really work. Not sure how we got into the habit of using it.


I got flag for not using it a couple of times when i worked for others and myself....


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## gold (Feb 15, 2008)

I did not know it wasn't approved for use outside. The Irony. The ONLY place I use it is on the weatherproof SEU connector above the meter. I would prefer using an RTV sealant there anyway but I wasn't sure if I could. I use RTV just about everywhere else tho so after this thread I think its time to move away from duct seal. Stuff is ugly anyway.

Thanks Bob your a stand up guy full of ... knowledge.


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## Jlarson (Jun 28, 2009)

BBQ said:


> As long as the right person approves it. :laughing:


I approve it.


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## gold (Feb 15, 2008)

captkirk said:


> I got flag for not using it a couple of times when i worked for others and myself....


I still get flagged occasionally for not using nolux.


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## BBQ (Nov 16, 2010)

Jlarson said:


> I approve it.


But you are a frigging roofer.
























:laughing:


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## Jlarson (Jun 28, 2009)

BBQ said:


> But you are a frigging roofer.
> 
> :laughing:


:lol:


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## wendon (Sep 27, 2010)

It must make a difference on what brand you use. I always use EPCO and this is their product description.

Asbestos-free compound.• Odorless, non-sticky formula.
• Can be painted immediately.
• Temperature tolerance: -40°F to 180°F.
• Excellent adhesive properties for use on wood, glass, aluminum and steel.
EPCO Duct Seal Compound is used to seal around junction boxes, flashings, service mast, and cable entries.
The Duct Seal Compound is available in individual 1 lb. Bricks, five 1 lb. Bricks in one package.


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## B4T (Feb 10, 2009)

BBQ said:


> Not sure what your point is.
> 
> The directions say not for outdoor use, traditionally it has been used outdoors.


Duct seal is a money maker for every electrician here.. :thumbsup:

It was the only compound used on watertight fittings that had SEU cable going into the meter pan...

They will ALL leak water over time.. enjoy a great payday.. :thumbup:


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## Semi-Ret Electrician (Nov 10, 2011)

wendon said:


> It must make a difference on what brand you use. I always use EPCO and this is their product description.
> 
> Asbestos-free compound.• Odorless, non-sticky formula.
> • Can be painted immediately.
> ...


Good catch:thumbsup:
So, the good stuff is not Ideal:laughing:


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## glen1971 (Oct 10, 2012)

varmit said:


> In answer to hardworkingstiff: Yes, "duct seal/ electrical putty" can be used as a sealing compound in Class 2 and 3 areas. In these areas the purpose is to block the travel of dust (Class 2) or lint (Class 3) and the seal is NORMALLY not required to be explosion proof. *A "C" fitting packed with duct seal is a common Cl 1, div 2, sealing method*.


Where?? Seen duct seal used lots in LBs going outside in general purpose and Class 1 Div2, but not in C's...What are you trying to seal?


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## varmit (Apr 19, 2009)

glen1971 said:


> Where?? Seen duct seal used lots in LBs going outside in general purpose and Class 1 Div2, but not in C's...What are you trying to seal?


Wall penetrations at area boundaries.


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## BBQ (Nov 16, 2010)

B4T said:


> Duct seal is a money maker for every electrician here.. :thumbsup:
> 
> It was the only compound used on watertight fittings that had SEU cable going into the meter pan...
> 
> They will ALL leak water over time.. enjoy a great payday.. :thumbup:


Interesting that you blame the duct seal and not the fitting that is UL listed as a wet location fitting.


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## glen1971 (Oct 10, 2012)

varmit said:


> Wall penetrations at area boundaries.


Ahh.. From inside to outside on a horizontal condiut rack? I had some vision of it being done at an end device for some reason...


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## Going_Commando (Oct 1, 2011)

BBQ said:


> Interesting that you blame the duct seal and not the fitting that is UL listed as a wet location fitting.


I know it. Pretty stupid that the gland in rain tight SE connectors expands over time, loosens on the cable, and allows water to enter the meter can. That's why I use unlisted RTV sealant around the gland in the listed fitting that doesn't do what the UL says it does.


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## brian john (Mar 11, 2007)

Emergency call today I had to buy 10lbs of duct seal.


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## BostonSparky (Jan 12, 2012)

brian john said:


> Emergency call today I had to buy 10lbs of duct seal.


This story needs pictures or more info.


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## Semi-Ret Electrician (Nov 10, 2011)

Applying duct seal in a conduit, at the low side, is a very inefficient way to stop a leak. 

Kind of like trying to patch a tire with bubble gum:laughing:


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## brian john (Mar 11, 2007)

Semi-Ret Electrician said:


> Applying duct seal in a conduit, at the low side, is a very inefficient way to stop a leak.
> 
> Kind of like trying to patch a tire with bubble gum:laughing:


Duct seal has no hydraulic rating therefore enough water in a conduit and whoosh..........


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## brian john (Mar 11, 2007)

BostonSparky said:


> This story needs pictures or more info.


10 conduits from roof mounted generator, routed in front of a AC vent then into the gear, condensation, and water dripping onto bus.

I bought rags, cable clean, duct seal. Only used the rags and cable clean and a high velocity fan to dry it up, seems to be a short term fix. Could not get in to use the duct seal.

We do not sell rags but we do sell CLOTHE WIPES.


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## ce2two (Oct 4, 2008)

captkirk said:


> I never understood that either. The name alone should be a clue.....DUCT seal..... i roll with silicone for sealing stuff


In concrete pull boxes where you have ridgid or pvc stubbed up, you use duct seal to keep out mice,rats,snakes etc, very common on all freeway lighting and all electrical underground installs on freeways around the country, this is fact, all are outdoors:thumbsup::laughing:


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## brian john (Mar 11, 2007)

ce2two said:


> In concrete pull boxes where you have ridgid or pvc stubbed up, you use duct seal to keep out mice,rats,snakes etc, very common on all freeway lighting and all electrical underground installs on freeways around the country, this is fact, all are outdoors:thumbsup::laughing:


I have seen HV splicers use duct seal when terminating to bus.


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## penfield (Jun 26, 2013)

*duct seal required*

My service installations must have duct seal in the weatherhead, on the top of the meter can around the hub, and where the SE cable penetrates the house......per the electrical inspector.


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## brian john (Mar 11, 2007)

penfield said:


> My service installations must have duct seal in the weatherhead, on the top of the meter can around the hub, and where the SE cable penetrates the house......per the electrical inspector.


A big :yawn: to your inspector.


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## Semi-Ret Electrician (Nov 10, 2011)

Let's see one brand of duct seal is bad & one is OK.

Q. Which one did you use.
A. The good one sir, but the UL label fell off.:laughing:


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## B4T (Feb 10, 2009)

BBQ said:


> Interesting that you blame the duct seal and not the fitting that is UL listed as a wet location fitting.


The fitting is useless without a sealing compound applied on top of it....

Using 100% silicone rubber *applied properly* will guarantee you no leaks..

Applied properly means using your finger to push the caulking into the connector so it "grips" entirely without any gaps behind the connector...

I carry blue disposable gloves to smear the silicone and not get it on my fingers.. :thumbsup:


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## Going_Commando (Oct 1, 2011)

B4T said:


> The fitting is useless without a sealing compound applied on top of it....
> 
> Using 100% silicone rubber applied properly will guarantee you no leaks..
> 
> ...


I just use my bare hands and lick my fingers clean. Silicone tastes just how it smells...delicious!


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## Barjack (Mar 28, 2010)

I use it on pool installations. It gets packed into the pipe that extends to the underwater light, at the bell box where it is spliced to the transformer. It keeps the chlorine away from the connection.

BTW, I don't think the inside of a weatherproof enclosure installed outdoors is "outdoors".


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## BBQ (Nov 16, 2010)

B4T said:


> The fitting is useless without a sealing compound applied on top of it....


Try using the right size and tightening it up.:whistling2:


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## B4T (Feb 10, 2009)

BBQ said:


> Try using the right size and tightening it up.:whistling2:


I always do.... but only a moron would leave it like that without any sealant applied on top.... IMO..


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## mbednarik (Oct 10, 2011)

I just install a conduit system for my service entrances to prevent such SEU leaking disasters.:whistling2:


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## Semi-Ret Electrician (Nov 10, 2011)

mbednarik said:


> I just install a conduit system for my service entrances to prevent such SEU leaking disasters.:whistling2:


Well now you got it started


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