We have decided to fit the fan in our bathroom in the ceiling, but we
are not 100% sure about what kind of extraction system is needed.
The plan is to fit a 6" in line fan in the roof and vent it like this:
But we were after a fan that has a humidity sensor/ movement sensor
for fully automatic operation but I cannot find an in line model like
Could we get a 6" centrifugal fan and vent it in the same way?
If so what are the advantages/dis-advantages of the two solution.
An inline fan with such facilities would be kind of pointless - unless
you want it to sense the humidity of your loft rather than the bathroom.
What you need is a standalone sensor like this :
That also puts the humidity control within reach rather than on the
ceiling or in the loft.
You can parallel a standalone PIR with the above as well if you want
motion detection as well.
Advantages of inline: freedom to chose an inlet vent of your choice
(TLC do a nice shower light combined vent for example), quieter
operation with less vibration. Pair it with whatever controls you fancy.
CF fan: not much to recommended it except you could possibly get a "one
box" solution with a built in humidistat (which would be at ceiling level)
Thanks for that.
I asked my Dad and we have decided to have just a PIR sensor, my Dad
says it should help to extract "fumes" when people use the toilet :-)
The bathroom is 9 meters squared, will a 5" fan be sufficient?
There is a trickle vent and a gap under the door.
AIUI the fan is activated by the PIR sensor, and then runs for a set
Will I need a separate timer?
Your help is appreciated.
IIRC The requirement for a bathroom fan is a flow of 15 litres per
second. Most fans will be able to do that.
Yup - as long as it has a permanent live as well as a switched one from
the PIR it should run on for a user selectable time. Note you will also
need a three pole isolator switch in the feed to the fan. If this is not
going to be in the same room as the fan then it should be one that can
be locked off.
On Tue, 24 Mar 2009 02:58:30 +0000, John Rumm wrote:
Fan sizeing is normally derived from room volume and so many changes per
hour. Fans are rated normally rated in cubic meters per hour. 15l/s is
54m^3/hr. *IIRC* bathrooms are reckoned to need 5 to 10 changes/hr so a
54m^3/hr fan is suitable for a tiny bathroom.
I just had a look through part F of the building regs, and the only
mention of data for bathroom intermittent mechanical extraction is the
15 l/s figure - they don't seem to take into account the room volume.
If you apply your 54 m^3 to a room of say 3x2x2m, that does in fact give
you 4.5 air changes per hour, which seems toward the upper end of what
would be required in a bathroom - especially without heat recovery.
Anecdotally, I have used a 4" humidistat fan in a bathroom with a high
pressure shower. I found that it would keep most of the visible steam
under control during the shower, and would have the room visibly clear
within 5 mins or finishing. It would then take 20 - 45 mins to dry the
all the room surfaces after that (that was all tiled, with two outside
non cavity walls).
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