ModCon Icing on Chimney

BobAlu

I guess one of the down sides of a mod con boiler is the icing that can occur up on the chimney. It appears that the moisture condenses on the stainless steel chimney cap and then drips and freezes. Any quick fixes here other than remove the chimney cap? Thanks!



Bob

Jamie Hall

In this weather?

You shouldn't be that surprised!  In fact even non-modcons can have condensation problems when it is this cold.  Unless the vent is actually getting blocked, I wouldn't worry about it myself.

R Mannino

I'm With

Jamie, as long as it never completely blocks it'll be fine. The ice should be gone by Sunday!

pipeking

WELL....

 if u like the look of the cap, and that's y u don't want to remove it, i would sugjust to drill a  3-9/16" hole thru the to off the cap and extent the vent thru it alittle then caulk around it.  by just extending it a little u won't see the pvc from the ground.

  also the condinsation that accurs on the cap and drips back down into the chimney can be corrosive to the masonry.

bill_105

Ditto

Has there not been enough hoopla over bad venting on this site ? I'd like to hear a mod/con manufacturer's rep say "That fine".

There is some artsy things you can do without tinkering with the exhaust flow.

Bob Harper

what's inside the flue?

What is this mod-con venting into? Is there pvc, stainless steel liner or just flue tile? 

R Mannino

FYI

CPVC

BobAlu

Thanks

For all the thoughts and comments! Just wanted to check with the pros if it's anything I should worry about. Hi Ron!



Bob

CMadatMe

Velocity Cone

Add a velocity cone to the pipe termination and cut an opening on the top of that chimney cover.

Zman

Don't like it...

Why not just drill a hole in the cap, run the pipe through and put a coupler and a screen on top?

I think the condensate could build enough ice to block the termination. What then?Is it worth taking the chance?

Do you really want all that vapor condensing on the cap and dripping down the clay pipe?

Carl

icesailor

Below freezing water vapor.

I will suggest that some of that ice is being formed by unfrozen pure water vapor (that can stay unfrozen to -40 degrees. The pure water vapor doesn't freeze until it has something to stick to and freeze. Like the frost on your car in the AM when cold or your getting radiational cooling.

There is no sign of freezing above the CPVC pipe under the cap. It is the ice on the outsides of the cap that seems to have caused the kerfuffle. I think it is a natural occurring phenomenon

Think clouds in the sky in the winter. Clouds are unfrozen water vapor. I flew to work the other day. It was 7 degrees on the ground. The weather was clear below 12,000 feet. It wasn't 35 degrees at 12.000 feet. It was pure water vapor. What causes hail is a speck of dust that the pure water vapor can stick to and gather ice. That ice on the chimney cap is a form of hail.

Don't worry about it.

Read this:



http://earthstorm.mesonet.org/materials/ref_watervapor.php

Another:



http://www.sciencedaily.com/releases/2011/11/111123133123.htm

Zman

Huh??

Do you know the difference between God and a Pilot?



God doesn't think he can fly a plane!



It is condensate and it can plug up the cap. I have seen it and it makes a mess. There is not a manufacture on the planet that would sign off on this detail.

I respectfully disagree

Carl

icesailor

Chimney icing:

Where did the writer say that the chimney was being blocked by Ice? (Crickets I think)

The issue was the ice on the outside of the screen. There is no ice on the inside of the vent. All the water vapor that is frozen on the side of the vent termination cage. My point in my post is that some of that ice may not be from the moisture in the flue gasses.

The vent ice has nothing to do with flying, just that there is moisture in the atmosphere that is available sometimes to add to the ice shown. I case someone didn't know that, I thought they might be interested. This is an information giving forum isn't it?

Here's more exhaust ice for you.

pipeking

i agree

  icesailer the pic u havealso have ice formations on the ground and sill, and thats from the exhaust. so what your saying is that the ice would still form if the exhaust wasn't there,right?

icesailor

Not necessarily.

Not necessarily. It heeds special conditions.

For example, the "wet" on the bricks could get ice to form on the side of the building if the conditions were perfect. The ice on the ground was more from the water vapor condensing and dripping on the ground. It was worse there at other times but there was someone around or a vehicle parked in front of it. I coouldn't take the photo until they were gone.

Henry

Certified manufacturer instructions

In both cases, I do not see venting installed as by the instruction manual of a the manufacturer of  the apliance! A square grill over CPVC, give me a break. It is illegal! I do not know of any manufacturer that allows venting to sent along a wall! It will destroy the mortar. Does anybody read instructions? Read the manual or contact the manufacturer if you are unsure!

Zman

Proper installation

I was thinking the purpose of this forum is to insure proper, safe installations. I don't see any on this post. Non meet manufactures specs. as Henry pointed out. I also don't see a whole lot of common sense. Insect screens, proper separation, approved terminations?

What happens when the roof termination ices up? The fan will push the gas somewhere. How about a bird nest or a kids toy (or rocks) in the side wall picture.

Let's all promote proper safe workmanship not "it otta work".

Carl

Bob Harper

chimney cap resistance and ice

That ss chimney cap is not an approved termination for any condensing gas appliance I'm aware of. Technically, it could be treated as a "shroud", which would require it to be listed with that appliance. This is a ForeverCap, which has a high static pressure compared to most other designs. NFPA 211 calls for a net free area 4x the area of the flue but that is for "chimneys". This std. does not consider placing a chimney cap over a condensing gas furnace flue gas outlet. Functionally, one can see where the ice is partially blocking the mesh on this cap further increasing the static pressure or making it harder to exhaust out of it. This cap is made of 304 stainless steel and will rot out from the acidic flue gases. Since PVC is not listed in the US (in Canada they have the S636 std.) there is no listed termination. Therefore, the code refers you to the listed instructions of the appliance. This plastic pipe would need a flashing so a water tight seal is made to keep water out of the flue. Much of the condensate that is not freezing is a dilute solution of carbonic and other acids. Acids generally do not freeze until supercooled. The do eat up the alkaline masonry. The acid can draw water from the interior of the brick to the face where the osmotic pressure can spall brick. Over time, the acid can eat away the hard fired face of the brick thus making it more porous and making it prone to freeze-thaw damage. 

icesailor

Flue Tile Venting:

You're absolutely correct.

That is actually a Poly flue pipe inside a tile lined chimney. Where is the air intake?

The cap is so screwey that it throws all reason to the wind.

CMadatMe

Guess Nobody Read

My post. I said cut and opening in the top of that cap and to

add a velocity cone to the pipe termination.