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Posted by Marc O'Brien - ACRTC on January 31, 2009, 10:55 am
On Jan 31, 12:25=A0am, "Marc O'Brien - ACRTC"
> On Jan 30, 3:04 pm, fullyabsorb...@gmail.com wrote:
> > 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 =96 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 =A0(204mm x 60mm). Assuming the existin=
g
> > 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
> 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.- Hide quoted text -
> - Show quoted text -
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 250m=B3/
hr through 100mm spiral over 1.5m will have a pressure drop of 72Pa
So your fan will have to be able to do 250m=B3/hr against at least 100Pa
external static.
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> 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 =96 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