Combi boiler vent on roof freezing up

[Flo]

We had a new condensing "VOKERA COMPACT HE" boiler installed a few years ago .unfortunately the company went bust so we can't ask them.the first winter the roof vent almost froze right up .the icicles hanging from the vent were extensive.the boiler never stopped working so I hoped it would if the vent eventually became frozen shut....is that correct .? Anyway during the last cold spell I decided to keep the boiler on low and on all the time but it didn't matter .the vented fumes still turned to water then froze over.i have no idea why nobody else in the street with a roof vent seems to have this bother and why doesn't the vents on other people's houses that are fitted on side walls have similar problems......

 

[AMGasServices]

Are you referring to the boiler flue or air vent ?

 

[diamondgas]

We had a new condensing "VOKERA COMPACT HE" boiler installed a few years ago .unfortunately the company went bust so we can't ask them.the first winter the roof vent almost froze right up .the icicles hanging from the vent were extensive.the boiler never stopped working so I hoped it would if the vent eventually became frozen shut....is that correct .? Anyway during the last cold spell I decided to keep the boiler on low and on all the time but it didn't matter .the vented fumes still turned to water then froze over.i have no idea why nobody else in the street with a roof vent seems to have this bother and why doesn't the vents on other people's houses that are fitted on side walls have similar problems......

Sounds like you're describing a vertical flue outlet yeh? I've noticed exactly the same on several condensing combi's. Down to the amount of condensate leaving the boiler and condensing as it leaves? Fumes evacuate differently from a vertical flue than from a horizontal. There's a larger surface area for them to condense on and I imagine this is where the water vapour forms in to droplets and gravity does the rest along with below freezing temperatures! The fume temps from conventional boilers are much higher and don't condense till they're away from the terminal.

 

[Flo]

Are you referring to the boiler flue or air vent ?[/
my mistake its the boiler flue on the roof that iam referring to.it looks like a black plastic tube about a foot long with rain cover.

 

[Flo]

Thankyou ,,,,,but I still am unsure if there is anything that I can do to prevent this from freezing up as in heating on all the time or intermittent or a different type of flue or re route the flue to outside wall.that would involve a long 3metre run of pipe which I have been advised against because iam told its meant to be the shortest route outside

 

[Flo]

Yep.its a vertical flue outside

 

[diamondgas]

Thankyou ,,,,,but I still am unsure if there is anything that I can do to prevent this from freezing up as in heating on all the time or intermittent or a different type of flue or re route the flue to outside wall.that would involve a long 3metre run of pipe which I have been advised against because iam told its meant to be the shortest route outside

I can't think of anything you could do to prevent this happening. Re-sighting the flue would be my thoughts too!

 

[stevetheplumber]

im unsure what the problem is do you feel its dangerous or unsightly?

 

[AMGasServices]

How far away is your boiler from an external wall ?

 

[Alpha man]

Could you take a pic of the flue outside and post it up on here?