I am about to put a range cooker in where my old boiler was, and as
part of this would like to install a 900mm wide extractor hood into the
chimney above the new range (the width of the chimney hole being 900mm
and depth 370mm). Naturally if I could pump the exhaust gas up the old
100mm boiler flue and out of the chimney, that would seem the most
logical solution.

Problem is I cant seem to find info on any manufacturer that supports
this configuration. Is the flue too long in such cases or is there some
other reason??

Anyway another option I would like to consider is having the motor
pulling the gases up the chimney, with the motor set into the top of
the chimney, rather than pushing up from the bottom, thereby removing
the noise too. Again, cant seem to find any info on this - on the web
anyway. Is it possible? Who supplies the gear to do it?

Any advice gratefully received as I really dont want to trunk the flue
halfway round the kitchen to find an external wall, when going up the
existing flue and chimney seems far more elegant.

Cheers,

Richard.

On 28 Apr 2006 10:54:36 -0700, "Richard"
wrote:


Problem is I cant seem to find info on any manufacturer that supports
this configuration. Is the flue too long in such cases or is there some
other reason??

One problem you will find is that with any significant length of
vertical flue you get a lot of oil/water condensate on the flue walls
which trickles back into the fan or on to the stove top. You also
need to fit a self closing fire damper at the bottom so if there is a
fire on the stove it can't propagate up the waste oils on the chimney
walls.

--
Peter Parry.
http://www.wpp.ltd.uk/

On 28 Apr 2006 10:54:36 -0700 someone who may be "Richard"
wrote this:-

Naturally if I could pump the exhaust gas up the old
100mm boiler flue and out of the chimney, that would seem the most
logical solution.

How long is this flue and what sort of terminal is fitted to the
top?

Problem is I cant seem to find info on any manufacturer that supports
this configuration.

I suspect that they all do, but don't want to be burdened with
responsibility for the design.

Does the hood have a grease filter? If it does then oil
contamination of the flue should be minimal and what is needed is a
suitable trap to stop condensate running back down to the mechanism.
These can be easily fashioned from standard components, but in
essence consist of a tee with the condensate led away to a suitable
container or drain. Any book or web page on vertical ducting should
explain what is necessary.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Thanks,

Flue is approx 30ft long (bottom to top of a two storey victorian
terrace, and the terminal is one of those louvred cylinder types - for
a standard gas boiler outlet.

Haven't bought a hood yet, so I guess i could look for one with a
grease filter. Is there any manufacturer who make a system desined for
such an installation? Will a standard motor be powerful enough to push
all the way to the top of the flue do you think?

Thanks for your help.

Flue is approx 30ft long (bottom to top of a two storey victorian
terrace, and the terminal is one of those louvred cylinder types - for
a standard gas boiler outlet.

Haven't bought a hood yet, so I guess i could look for one with a
grease filter. Is there any manufacturer who make a system desined for
such an installation? Will a standard motor be powerful enough to push
all the way to the top of the flue do you think?

We had a similar issue with a terraced house and a bathroom move. We
needed to fit a new air extractor fan in the bathroom and for ease of
fitting the builder suggested going into chimney breast.

I insisted on either a roof vent or going out through the wall. A
friendly corgi registered fitter was in the house recently and his
comments after seeing the work and hearing the builders suggestion was
unprintable. Basically venting into an existing flue can be dangerous
as if there is any leakage from the neighbouring properties flue any
fumes could come back into the bathroom. He had seen combi boilers
venting into chimney flues before and condemned the installations.

On 30 Apr 2006 04:47:14 -0700 someone who may be
wrote this:-

Basically venting into an existing flue can be dangerous
as if there is any leakage from the neighbouring properties flue any
fumes could come back into the bathroom. He had seen combi boilers
venting into chimney flues before and condemned the installations.

You are perhaps mixing up chimneys with flues. Though the latter may
be inside the former there is a difference.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 30 Apr 2006 02:18:11 -0700 someone who may be "Richard"
wrote this:-

the terminal is one of those louvred cylinder types - for
a standard gas boiler outlet.

Then water will condense on the underside of the terminal and drip
back down. A trap will deal with this.

Is there any manufacturer who make a system desined for
such an installation?

All the serious suppliers will make such systems for commercial
kitchens.

Will a standard motor be powerful enough to push
all the way to the top of the flue do you think?

That depends on the type of fan that is fitted. The right sorts of
the right size should have no problem. The manufacturers put graphs
of this sort of thing in their information.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Basically venting into an existing flue can be dangerous
as if there is any leakage from the neighbouring properties flue any
fumes could come back into the bathroom. He had seen combi boilers
venting into chimney flues before and condemned the installations.

You are perhaps mixing up chimneys with flues. Though the latter may
be inside the former there is a difference.

Sorry David - perhaps got that wrong. If venting (boiler, extrator
whatever) into a chimney would you be OK if you put a flue liner in
place?

Basically venting into an existing flue can be dangerous
as if there is any leakage from the neighbouring properties flue any
fumes could come back into the bathroom. He had seen combi boilers
venting into chimney flues before and condemned the installations.

You are perhaps mixing up chimneys with flues. Though the latter may
be inside the former there is a difference.

Sorry David - what is the difference between a chimney and a flue -
don't all operating chinmeys use a flue?

On 2 May 2006 14:45:31 -0700 someone who may be
wrote this:-

If venting (boiler, extrator
whatever) into a chimney would you be OK if you put a flue liner in
place?

A suitable flue inside a chimney, going directly from the equipment
to a suitable terminal, is no different to one outside the chimney
as far as exhausting gases.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On 2 May 2006 14:45:59 -0700 someone who may be
wrote this:-

what is the difference between a chimney and a flue

The terminology is slightly different in different fields, which
makes it confusing. However, a flue from an appliance is a tube,
usually made of metal, that takes the gases outside without them
mixing with other gases.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

A friend did this in a terraced house for his kitchen range. Put a
light in the chimeny also. Just used a regular extractor fan (not hood)
I think. No problems after two years.


David Hansen wrote:
On 2 May 2006 14:45:59 -0700 someone who may be
wrote this:-

what is the difference between a chimney and a flue

The terminology is slightly different in different fields, which
makes it confusing. However, a flue from an appliance is a tube,
usually made of metal, that takes the gases outside without them
mixing with other gases.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54