Ice buildup on chimney

bmaclean

Hello,

I have a Viessmann Vitola 200 boiler which runs off of NG - the boiler is around 6 or 7 years old. It is connected to a stainless liner. When the temperatures are quite cold, there is a great deal of ice buildup - I have attached a picture of the buildup - it does get worse than what is shown in the photo. In the photo, the flue on the right is the fireplace, and the flue on the left is from the boiler.

One of the reasons I have started to pay attention to the ice buildup is I recently replaced the cap on top of the chimney as it was falling apart - I believe I know the reason.

First quetion is whether or not this is a problem I should be concerned about? If so, what do I need to do to remedy the situation? Insulated liner? Other?

Thanks.

Jamie Hall

When it's cold enough, the stack gas will condense when it hits the open air. Nothing much to be done about it. A condensing boiler does its condensing in the boiler -- as the name implies -- but again if it is cold enough, it can't condense as you need the heat in the house, and the condensation happens at the top. You might try -- if it really is a problem -- a higher termination.

bmaclean

Well, I still have an ice problem. There have been a couple of changes that I hoped would fix the ice problem. First, the liner was a 6" liner and by the Viessmann manual, it should have been 5" so that was replaced. As well, the cap was changed to a different design - the new one doesn't have a full cap - it is a couple of concentric rings. Finally, the chimney was insulated with thermix.

Is there anything else to try? Perhaps changing the height of the flue? (probably the wood fireplace flue height would also have to be changed). I searched this forum and there was a mention of ice and a short cycling boiler - how long would the cycles need to be to be considered short?

Any other ideas?

Gordy

You have done all you can with properly sized flue, and insulating it.

What the picture does not show is if this is a three sided exterior chimney, or an interior chimney.

bmaclean

Hi, this is a 3 sided exterior chimney.

Thanks.

Gordy

From grade to roof being four sided from roof to termination?

Exterior wall chimneys are an Achilles heel as to keeping them warm between cycles. I would say you have done all you can. Newer more efficient boilers with lower stack temps, and less stand by losses make it worse.

Henry

Here is a little problem
with the new 10 to 1 turndown condensing boiler.

NY_Rob

^ Is that the exhaust?

Brewbeer

Is a direct vent through a sidewall an option with this boiler?

Also, I've been told that a chimney is not a good place to mount an antenna, as wind action tends to flex them causing bricks to loosen up.

bmaclean

Gordy said:

From grade to roof being four sided from roof to termination?

Exterior wall chimneys are an Achilles heel as to keeping them warm between cycles. I would say you have done all you can. Newer more efficient boilers with lower stack temps, and less stand by losses make it worse.

It is 3 sided from grade to the roof, then 4 sided from the roof to the top of the chimney.

Thanks.

bmaclean

Brewbeer said:

Is a direct vent through a sidewall an option with this boiler?



Also, I've been told that a chimney is not a good place to mount an antenna, as wind action tends to flex them causing bricks to loosen up.

Yeah, I think direct vent is an option and maybe is something I need to consider at some point.

Every chimney expert who has seen the antenna has always told me that it isn't a great idea - I put it up quite some time ago as an experiment and if it became permanent, I was going to move it to the roof. It became permanent and I have not had a chance to move it .

flat_twin

The antenna folks would tell you it's not great for the electronics either