Charnwood Downdraft fix with external air vent.

[topchippyles]

Your pipe is not high enough above the ridge line and that is the hetas regulations which is a minimum of 1 meter  . Had the same problem as i have a very steep pitched roof and extended the flue and fitted a H cowl problem solved. Look on the hetas website and it will show you the diagram and spec sheets. 

Edited January 5, 2021 by topchippyles

[Cowmop]

Thought it was law to have a wall vent in the room the wood burner is in?

[andy cobb]

27 minutes ago, Cowmop said:

Thought it was law to have a wall vent in the room the wood burner is in?

Think only for above 5kw stoves or installations in any modern airtight house 

[Cowmop]

Bizzarly we got the cavity walls insulated and the people who did this fitted the vent to the front room where the wood burner is.

[topchippyles]

Normally a vent fitted but the installer should be on the ball with that (regs)

[openspaceman]

On 02/01/2021 at 19:50, Gtflash said:

CO alarm went off at 3am about three weeks ago so

 This is a bit worrying. From what you say when successfully lit there is no problem. We have discussed how these modern stoves have a tortuous path for the air to get in as it needs to be preheated before being injected down the glass or as jets through the back, so the flue has to contain hot gases before it pulls enough draught to overcome the resistance.

 

It also seems there must be a thermosyphon happening such that as the fire cools  cold air is coming down the flue, bringing combustion products into the room  as it replacing hotter air leaving the house through something like a batthroom vent.

 

I would think having the stove room-sealed with cold combustion air from the outside is the safe solution.

Edited January 5, 2021 by openspaceman
hyphenation

[Gtflash]

21 hours ago, slim reaper said:

If thats the cowl you have,the one in the last pic ,its just a rain hat and totally useless for downdraft.Is the flue higher than the ridge?

@slim reaper  that’s the old cowl.  The one he put on is the earlier library picture.  Checked height above ridge this evening from across the road, with a good eye balling. bottom of cowl is maybe 500mm above ridge. Then cowl is 100-150 ish.  

[Gtflash]

12 hours ago, andy cobb said:

Think only for above 5kw stoves or installations in any modern airtight house 

Yep I believe over 5kw.  Mine is 5kw unit.  Big room 8x5m

[Gtflash]

@openspaceman

 

I feel a direct vent might give the stove it’s own balanced system and help it.  Is there any disadvantage to direct air supply??  I’ve Googled loads and not really found any. 

 

fires lit last 2 days now.  Winds changed to NE and I’ve ditched newspaper and using 4 natural wax dipped fire lighters.  The wife stands by window and opens it if the fire lighters don’t roar straight away.  To be honest though there’s been no visible draft down chimney 

Edited January 5, 2021 by Gtflash

[Gtflash]

13 hours ago, topchippyles said:

Your pipe is not high enough above the ridge line and that is the hetas regulations which is a minimum of 1 meter  . Had the same problem as i have a very steep pitched roof and extended the flue and fitted a H cowl problem solved. Look on the hetas website and it will show you the diagram and spec sheets. 

I don’t think the top of stack is  1m above my ridge but I have only eye balled it..  I will have a look at regs but I really trust his install.  I watched him measure the co alarm position with pin point accuracy. 

Edited January 5, 2021 by Gtflash