Substantial Ice Buildup On Chimney: Why?

CTYankee

FIrst winter with new boiler (EK) which has outside combustion air intake. I recently noticed a substantial buildup of ice at the top of the chimney. Could this possibly be normal? Is it due to taking in outside air for combustion? I have ice dams forming on the roof adjacent to the chimney at this point. Please explain this to me. Thanks

Mad Dog_2

Probably condensation from flue product. Do you have a SS liner? Pictures of boiler please. Mad Dog

CTYankee

Yes, SS liner. Here is pic of boiler:

leaking

chimney won’t get hot enough and gas is hitting the cap . Could it freeze enough to stop the boiler ? I don’t know but I would be concerned enough figure it out. That chimney cap needs to go , just my opinion. The gas hits chimney cap, cools , and isn’t blowing away in low wind . Gas needs to go up and away, not hit a cap that’s to low .

GW

Ice damming seems unrelated to the main topic; your house is losing heat

Intplm.

When was your last tune up/service? What was the stack temp?

Nice system 2000.

mattmia2

that is like the pillar of ice underneath the direct vent appliance out the side wall. there is plenty of space for the combustion products to mix with the cold, dry air and for evaporation to cool the products further to get it cold enough to freeze to the cap. the cap is a huge heat sink that takes heat away and conducts it in to the air. a small single flue chimney is not likely to do that, but with the 3 flues there is a lot of area compared to the size of the heating flue.

there could have been some snow that has since melted that collected up there that helped it form too.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1886875#Comment_1886875

ice dams are a combination of not enough attic ventilation for the amount of ventilation in the attic. if the outlet vent is a ridge vent those tend to get covered with snow and stop working in the type of winter with lots of snow we have had in michigan this year.

CTYankee

OK: starting to make sense.. Contractor indicated reason for the liner was due to flue temps with new system being way lower than with the old 1960's boiler. The flue gases are hitting the screen on the cap and condensing, leading to ice formation (is was minus 1 degree here this AM). I am thinking eliminating the screen part of the cap might solve issue. We put the cap on a number of years ago to protect crown from rain water: never had a problem with birds or squirrels so I think we can live without the screen. Sounds like it goes on the project list for the spring. Thanks all!

pecmsg

is it preventing the unit from operating?

We don’t get weather like this often.

CTYankee

Boiler is still operating: hope it continues until the temps warm up: it would be no fun up on that roof with the snow at this point.

leaking

don’t just remove the screen , the cap is way to low , it should go in my opinion. You need the chimney gas to go up and not hit a piece of metal 6” higher . What worked before won’t work now . Talk to boiler manufacturer they deal with this every day .

GW

I’m making the assumption the previous boiler also utilized combustion air. This boiler uses air that causes ice damming? It’s a colder winter, there’s actually snow this year

mattmia2

the oild boiler was probably constantly drafting house air up the vent and keeping it warmer. with the new boiler sealed there is no house air to warm it during the off cycle.

Jamie Hall

Baby it's cold outsde, and the moisture in the boier exhast is freezing on the first cold thing it hits. If you need to keep critters out of the chimney — which is a good idea — a flat screen across the top will d (I'd suggest half inch mesh, wire of course).

Will it freeze shut? I veery much doubt it — even in this weather.

GW

not sure how that relates to ice damming on the roof

mattmia2

https://forum.heatinghelp.com/discussion/comment/1886910#Comment_1886910

the ice damming is a separate issue with attic ventilation and insulation.