Fitting a mushroom vent

[luggsy]

Is there a set rule on how far you can fit a mushroom vent from your flue, I am looking to fit another vent but where I want to fit it it is about 20" inches from the flue , stove is a diesel reflex thanks in advance 

[Sea Dog]

7 hours ago, luggsy said:

Is there a set rule on how far you can fit a mushroom vent from your flue, I am looking to fit another vent but where I want to fit it it is about 20" inches from the flue , stove is a diesel reflex thanks in advance 

I don't know about any rule, but common sense would seem to suggest that 20" is a bit close unless you particularly like the smell of diesel fumes. 

[Jen-in-Wellies]

When I fitted out my boat it was to meet the 2005 edition of the Boat Safety Scheme valid at the time, rather than the RCD. I seem to recall that there was a minimum flue to air vent distance in there, but I can't remember what it was and no longer have a copy. The latest revision makes no mention and has removed a lot of the ventilation requirements and made what remain largely advisory for private boats. If anyone still has a copy of the 2005 edition they may be able to check my limited and inadequate memory. The BSS web site used to link to it, but it now comes up 404 Not Found and only links to the current requirement. There may be something in the RCD requirements, but these are spread over a whole load of different standards.

I would second Sea Dog. 20" is too close and likely to get smelly diesel fumes in the cabin. Diesel engines emit very little carbon monoxide, but I have no idea about Reflex stoves. Would depend if combustion is air rich, fuel limited, like diesel engines, or fuel rich, air limited, like solid fuel stoves. With solid fuel stoves the distance is important as fumes will have lots of CO. Is the 20" edge to edge, or centre to centre of the flue and mushroom?

 

Jen

Edited November 23, 2018 by Jen-in-Wellies

[dor]

Doing my RCD in 2008, I'm pretty sure the distance was 50cm as the surveyor overseeing my build mentioned it.  Of course it might have been changed since.  I've got an idea it was edge to edge.

[Phil Ambrose]

Can't ever remember an inspector checking out my flue and distance from vents.

Phil

[LadyG]

4 hours ago, Phil Ambrose said:

Can't ever remember an inspector checking out my flue and distance from vents.

Phil

Well that's a relief

[David Mack]

6 hours ago, Jen-in-Wellies said:

When I fitted out my boat it was to meet the 2005 edition of the Boat Safety Scheme valid at the time, rather than the RCD. I seem to recall that there was a minimum flue to air vent distance in there, but I can't remember what it was and no longer have a copy. The latest revision makes no mention and has removed a lot of the ventilation requirements and made what remain largely advisory for private boats. If anyone still has a copy of the 2005 edition they may be able to check my limited and inadequate memory. The BSS web site used to link to it, but it now comes up 404 

 

It's still on the BSS website under "Non Private Boats"

 

"To minimise the risk of flue gases re-entering a boat, flue terminals and air inlets should not be positioned within 500mm (20ins) of ventilators, opening ports, hatches, or windows. There is also a risk that flammable vapours could be drawn down into an appliance and for this reason the same separation of flue terminals/air inlets from re-fuelling fittings or fuel tank vent outlets is recommended."

 

See https://www.boatsafetyscheme.org/boat-examination/non-private-boats/part-8-appliances,-flueing-ventilation/flue-components,-room-sealed-appliances/

Edited November 23, 2018 by David Mack

[WotEver]

1 hour ago, David Mack said:

 

It's still on the BSS website under "Non Private Boats"

 

"To minimise the risk of flue gases re-entering a boat, flue terminals and air inlets should not be positioned within 500mm (20ins) of ventilators, opening ports, hatches, or windows. There is also a risk that flammable vapours could be drawn down into an appliance and for this reason the same separation of flue terminals/air inlets from re-fuelling fittings or fuel tank vent outlets is recommended."

 

See https://www.boatsafetyscheme.org/boat-examination/non-private-boats/part-8-appliances,-flueing-ventilation/flue-components,-room-sealed-appliances/

So it would be sensible to follow that guide even though it’s non-compulsory. 

[Matt&Jo]

What about if you had a tall flue......would that not make any difference?

I know smoke is made up of gasses and solids but i doubt it would fall that fast...ive seen lots of very tall flues on boat

[Jen-in-Wellies]

3 hours ago, Matt&Jo said:

What about if you had a tall flue......would that not make any difference?

I know smoke is made up of gasses and solids but i doubt it would fall that fast...ive seen lots of very tall flues on boat

Only if the flue was fixed, or the stove were interlocked, so it could not be run with it removed perhaps. Similar to opening windows not counting to fixed ventilation area. When the windows are closed the ventilation disappears. Looking for what is safe and sensible, rather than what loophole can be used to get round something.

[ditchcrawler]

Well it seams a strange regulation, we left our boat Thursday morning, no wind and below zero temperatures. The boat a short distance behind us had their fire alight and the smoke curling out of their 18" tall chimney with a Chinaman cap on it was sinking down and rolling along the roof of the boat, probably it was only within 20" of the flue that was clear.

[Sea Dog]

10 hours ago, ditchcrawler said:

Well it seams a strange regulation, we left our boat Thursday morning, no wind and below zero temperatures. The boat a short distance behind us had their fire alight and the smoke curling out of their 18" tall chimney with a Chinaman cap on it was sinking down and rolling along the roof of the boat, probably it was only within 20" of the flue that was clear.

Ha! You can't legislate for that, eh? Mind you, I don't care if the regulations say that 20" is ok, I still think common sense suggests you need a decent gap between a vent and a chimney.