I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the
outside (mainly for aesthetic reasons) and wonder if there's a way of
ducting the two together so they both exit via the same grille? I'm
imagining a large Y-connector with built-in one-way valves... does
anything like this exist?

Thanks
David

Not quite a Y-connector, but Domus do a T-connector and separate dampers.

I recently ordered some of their 125mm ducting from http://www.bes.ltd.uk/.

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the outside
(mainly for aesthetic reasons) and wonder if there's a way of ducting the
two together so they both exit via the same grille? I'm imagining a large
Y-connector with built-in one-way valves... does anything like this exist?

Thanks
David

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the
outside (mainly for aesthetic reasons) and wonder if there's a way of
ducting the two together so they both exit via the same grille? I'm
imagining a large Y-connector with built-in one-way valves... does
anything like this exist?

I've seen 4" Y connectors as you describe in my local plumbers merchants but
never 5". Have a chat with yours to see if there are 5" ones on special
order.

Just out oif interest - where did you get your 5" fan from? TLC?

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the
outside (mainly for aesthetic reasons) and wonder if there's a way of
ducting the two together so they both exit via the same grille? I'm
imagining a large Y-connector with built-in one-way valves... does
anything like this exist?

Thanks
David

NotMe wrote:

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the
outside (mainly for aesthetic reasons) and wonder if there's a way of
ducting the two together so they both exit via the same grille? I'm
imagining a large Y-connector with built-in one-way valves... does
anything like this exist?

Just out oif interest - where did you get your 5" fan from? TLC?

No, Screwfix
(http://www.screwfix.com/app/sfd/cat/...48 8&ts=07844)

David

Tom wrote:
"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the outside
(mainly for aesthetic reasons) and wonder if there's a way of ducting the
two together so they both exit via the same grille? I'm imagining a large
Y-connector with built-in one-way valves... does anything like this exist?


Not quite a Y-connector, but Domus do a T-connector and separate dampers.

I recently ordered some of their 125mm ducting from
http://www.bes.ltd.uk/.

Thanks a lot Tom: yes that would certainly do the trick; surprised they
don't do a Y rather than a T as I would imagine the 90-deg will not do
wonders to the airflow.

David

On Thu, 20 Jan 2005 08:08:25 GMT, Lobster
wrote:

Tom wrote:
"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the outside
(mainly for aesthetic reasons) and wonder if there's a way of ducting the
two together so they both exit via the same grille? I'm imagining a large
Y-connector with built-in one-way valves... does anything like this exist?


Not quite a Y-connector, but Domus do a T-connector and separate dampers.

I recently ordered some of their 125mm ducting from
http://www.bes.ltd.uk/.

Thanks a lot Tom: yes that would certainly do the trick; surprised they
don't do a Y rather than a T as I would imagine the 90-deg will not do
wonders to the airflow.

David

Yes, a Tee would be really restricting on the flow.

I've just been designing and installing dust extraction for my
workshop using steel ducting. The application is more onerous than
room extraction because there is a lot more air as well as dust and
chippings to move, however, the principles are the same.

While there are tees available, they are strongly discouraged because
they have an enormous effect on air flow. In my set-up I have Y
branches (at 60 degrees between the legs, 30 degrees each to the
common output) and branches at 30 degrees, then where I need to make a
right angle, a further 60 degree branch is added some distance away.

The other factor, is if you are going to combine two fan outputs at
125mm each, you need to raise the size of the outlet to the outside so
that you don't create even more flow resistance and back pressure.

If you work out the area of two 125mm ducts, to achieve equivalent
area, the duct needs to be 177mm. The nearest standard size to that
is 180mm, so really, the combined output should be that size. On a
short length, you could probably get away with 160mm for the combined
bit if it's short.

I used ducting made by Nordfab (www.nordfab.com), sold here by DISA
Airmaster (www.disaairmaster.com) in metric sizes. There are
certainly Y branches, and they will make up whatever you want.
However, this is galvanised steel in quite heavy gauge, so
over-engineered for what you want and probably even galvanised steel
is not a good idea with moist air in the long term. Not cheap either
- a y branch like this would probably cost around £80.

However, I think that this is the right industry area, and you could
probably find something from a supplier of air conditioning ducting.
These people (http://www.abbeyairsystems.co.uk/index.html) were
helpful when I called them although I didn't buy anything there. They
seem to have duct and fittings in PVC, which is what you want, I
think.

Another option could be to use 160mm soil pipe and fittings, although
looking at the prices, that is an expensive hobby also, even to buy
just the pipe and fabricate something.

You could also make up a plenum chamber from WBP ply with connectors
joining at shallow angles, and the interior painted with a sealer.
This would be cheap to make, albeit a little time consuming.

This site has a bunch of ideas and references where you might find
something useful

http://billpentz.com/woodworking/cyclone/Ducting.cfm


It's also important to insulate any of this and ductwork in the loft
so that you don't get condensation.






--

..andy

To email, substitute .nospam with .gl

Lobster wrote:
Tom wrote:

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing
to fit a second such fan close by. However, I would prefer not to
have to make a second hole through the wall to fit a second grille on
the outside (mainly for aesthetic reasons) and wonder if there's a
way of ducting the two together so they both exit via the same
grille? I'm imagining a large Y-connector with built-in one-way
valves... does anything like this exist?


Not quite a Y-connector, but Domus do a T-connector and separate dampers.

I recently ordered some of their 125mm ducting from
http://www.bes.ltd.uk/.

Thanks a lot Tom: yes that would certainly do the trick; surprised they
don't do a Y rather than a T as I would imagine the 90-deg will not do
wonders to the airflow.

Forgot to ask - are these dampers essentially one-way valves (which is
what I'd need?)

Andy Hall wrote:
On Thu, 20 Jan 2005 08:08:25 GMT, Lobster
wrote:

"Lobster" wrote in message
news
I'm about to knock a hole through the end wall of the house, in the
roofspace above the bathroom, to take the output of a 5" extractor fan.

After the job's done and tested, I suspect I may find myself needing to
fit a second such fan close by. However, I would prefer not to have to
make a second hole through the wall to fit a second grille on the outside
(mainly for aesthetic reasons) and wonder if there's a way of ducting the
two together so they both exit via the same grille? I'm imagining a large
Y-connector with built-in one-way valves... does anything like this exist?


The other factor, is if you are going to combine two fan outputs at
125mm each, you need to raise the size of the outlet to the outside so
that you don't create even more flow resistance and back pressure.

If you work out the area of two 125mm ducts, to achieve equivalent
area, the duct needs to be 177mm. The nearest standard size to that
is 180mm, so really, the combined output should be that size. On a
short length, you could probably get away with 160mm for the combined
bit if it's short.

Thanks a lot for all the really useful info Andy. Must admit I hadn't
thought about the need for a larger outlet to take 2 inputs, but TBH
it's more than likely that if I fit the second fan, it will be not be in
use at the same time, so I should be OK. Think I've satisfied myself
that I only need to knock through one hole in the brickwork anyway,
which is what I really needed to know at this stage! I'll certainly
revisit your post if it turns out I need (or more plausibly, SWMBO
decrees it) the 2nd extractor.

David