I need to extract 247 cubic metres per hour from my bathroom. I will
be using a 150mm (6") ceiling fan capable of extracting 250 m3/ph
(Solar and Palau Silent 300). I have a 1.5 metre run. Currently I have
100mm (4") circular flexible hose already installed. Will this
existing hose be sufficient for the job? If it is I intend to use a
150mm – 100mm reducing spigot. I have read that 100mm is sufficient
for up to 250m3/ph but i have not been able to confirm this.
Increasing the diameter of the hose will tricky because of the
configuration of the void space through which it will travel. The
wider the diameter the bigger the problem. If I go larger than 100mm
hose I will need to use rectangular flexible hose. The ideal option
(180mm x 90mm) is not available as rectangular flexible hose.
It seems that the only rectangular flexible hose options are options
available are (150mm x 70mm) or (204mm x 60mm). Assuming the existing
hose i have is not sufficent, is the 150mm x 70mm enough or do i need
to use the 204mm x 60mm.
Many thanks for you help
On Jan 30, 3:04 pm, firstname.lastname@example.org wrote:
The 100mm flexi hose at 1.5 meters will offer a lowest resistance of
25Pa if fully extended with no bends. The transition 150 to 100 might
offer another 5Pa (off the top of my head). So you fan would have to
be capable of at least overcoming 30Pa. Grills and diffusers worst
case might be another 20Pa each.
The 150mm x 70mm will amount to precisely the same thing.
The 204 x 60 would have a pressure drop 80% that of the 100mm flexi.
But transitions and grills etc remain.
Actually, looking at my recent copy of the NEBB TAB book it lists
spiral duct roughness as 3mm and not as 0.3mm presented to me a few
years back in a suppliers catalogue.
Changing my software to reflect this I instead no calculate that 250m³/
hr through 100mm spiral over 1.5m will have a pressure drop of 72Pa
So your fan will have to be able to do 250m³/hr against at least 100Pa
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