DIYbanter - boiler question

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I have an open flued boiler at the moment. The boiler sits in an
internal cupboard with the flue going straight up through the attic
space and outside through the roof. I am thinking of replacing the
boiler with a newer model. Could i fit a boiler with a fanned flue while
keeping the existing flue pipes? Am i right in thinking that a FF system
is room sealed and safer than an OF system?

Thanks in advance...

Gerry

Could i fit a boiler with a fanned flue while keeping the existing flue
pipes?

No. However, if the existing flue pipe is straight, it might be possible to
shove a new flue pipe up the middle, with a new termination on the top. Best
for this would be models that can use high temp drain pipe as the flue, as
they can often have the exhaust go up the chimney and have air supply
through the wall.

Am i right in thinking that a FF system is room sealed and safer than
an OF system?

Yes.

Christian.

On Tue, 01 Feb 2005 10:20:01 +0000, Dr Evil wrote:

"Cuprager" wrote in message
...
I have an open flued boiler at the moment. The boiler sits in an
internal cupboard with the flue going straight up through the attic
space and outside through the roof. I am thinking of replacing the
boiler with a newer model. Could i fit a boiler with a fanned flue while
keeping the existing flue pipes? Am i right in thinking that a FF system
is room sealed and safer than an OF system?

Thanks in advance...

You can us the existing pipes. Some boilers, Keston is one, use two plastic
drain pipes for the flue. The exhaust may go up the existing flue pipe and
terminate over the roof. The problem is the other air inlet pipe. which can
be routed maybe under a floor to the outside. the two pipes do not have to
be terminated at the same place. This is great for flexible fluting.

Provided the flue is straight and access to the terminal is not
prohibitively expensive. The sections will have to be jointed and lowered
into the flue from above. There are some minor restrictions on the
placement of the flue and air duct terminals.

My guess is that in almost every location there will be some very good
reason why using the existing flue is not practical.

Other manufacturers can use plastic flues albeit with a (possibly)
expensive option adaptor.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

"Cuprager" wrote in message
...
I have an open flued boiler at the moment. The boiler sits in an internal
cupboard with the flue going straight up through the attic space and
outside through the roof. I am thinking of replacing the boiler with a
newer model. Could i fit a boiler with a fanned flue while keeping the
existing flue pipes? Am i right in thinking that a FF system is room sealed
and safer than an OF system?

Fan Flued boilers are effectively room sealed so yes you are correct in
saying they are safer.
It would depend on many factors but the usual fan flued models employ a
concentric system whereby the inner tube conveys flue gases out of the
building and the outer tube conveys combustion air from outside to the
boiler. Different manufacturers have different standard requirements as to
maximum length permitted (with equivalent lengths for elbows etc). As you do
not mention whether the building is a bungalow or a house or which floor it
is on I can't be any more specific. I can say that if it is within the
maximum equivalent length for whichever boiler you choose then the route of
the old flue may be usable but the actual old flue pipe is unlikely to be
usable.
Some boilers can use two seperate pipes which allows greater flue and intake
lengths so you do have greater options for flexiblity. Also worth looking at
are versions of the Ideal Vertex flue system which uses a concentric fan
flue into the loft space where combustion air is drawn in then a single flue
outlet tube passes through the roof to a discharge point.
I suggest you look into suitable boilers then ask the manufacturer for the
available flueing options for that (those) models

HTH

snip
.. As you do
not mention whether the building is a bungalow or a house or which floor it
is on I can't be any more specific.

We live in a 1900's sandstone built flat. We are on the top, the boiler
sits in an internal cupboard and the flue goes straight up through the
ceiling and out through the roof without any bends or elbows it
terminates with a 'pointy hat' type of cowl. I guestimate that the flue
pipe will be around 3m in length.

Thanks for all your input. I think i would like to go down the FF route
as i don't really like having an OF boiler in the living space... don't
know if this notion is properly founded or just me being paranoid though!

"Cuprager" wrote in message
...
snip
. As you do
not mention whether the building is a bungalow or a house or which floor
it is on I can't be any more specific.

We live in a 1900's sandstone built flat. We are on the top, the boiler
sits in an internal cupboard and the flue goes straight up through the
ceiling and out through the roof without any bends or elbows it terminates
with a 'pointy hat' type of cowl. I guestimate that the flue pipe will be
around 3m in length.

Thanks for all your input. I think i would like to go down the FF route as
i don't really like having an OF boiler in the living space... don't know
if this notion is properly founded or just me being paranoid though!

Sounds ideal for a vertical fan flued option so you can either do the job
before April 1st if you want to use non condensing technology or timing is
immaterial if you opt for condensing. Think about Glow worm condensers
amongst others as they are well made, simple installation and stainless
steel heat exchangers.