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We had some mould appear in our bathroom and I suspected that our inline extractor fan was underpowered. As it happens the extractor just stopped working, so I'm in the market for a replacement.

I have a few questions:

  • What is better - centrifugal or induct? It looks like the centrifugal ones have best throughput but are they as reliable etc?
  • What rate is good? I can't find info on my old induct 23W fan's rate, but I assume it was in the range 80-100 m^3/hr - does that sound about right? Would going up to a 220 m^3/hr be excessive?
  • Does power affect anything other than the rate?

A few notes:

  • The inlet in the bathroom is in the ceiling
  • I don't really want to take out the old ducting & fittings, so if it was a round, 125mm fan that would be great. Also 100mm would work I guess as I could still make the ducting fit.
  • Fan needs to have an adjustable timer on it so it stays on after the light is turned off - there is a permanent live circuit available.
  • Bathroom is approx 1.6m x 2.5m x 2.2m (i.e. 8.8 m^3) Using some recommendations from another answer, this would mean 70 m^3/hr would be fine... but it's not worked out that way before. Perhaps the timer wasn't on for long enough? Or perhaps I can double the throughput and halve the time?
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How big is your bathroom? –  Niall C. Sep 13 '12 at 11:06
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This answer might help you determine what size fan you need. –  Tester101 Sep 13 '12 at 11:09
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Whatever you do, pay close attention to the noise level. A fan that is too loud will not be used. Unfortunately, silence is golden. Which means it costs lots of gold. –  Chris Cudmore Sep 13 '12 at 13:29
    
@NiallC - have added the info. –  x3ja Sep 13 '12 at 15:15
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the other thing you need to take into account is how long the duct run is and how many bends are in it. Longer runs/more bends means you need a higher powered fan. Also make sure its not blocked! –  Steven Sep 13 '12 at 20:18

1 Answer 1

up vote 0 down vote accepted

In the end I went for a mixed flow (which I think is both cetrifugal & radial or something), has about double the throughput that is recommended for the size of room (240 m^3/hr vs 110 m^3/hr). Doesn't have a timer on it, but it seems to be keeping the steam down when we shower anyway.

Here's a link to the fan I bought in the end.

Thanks for the pointers.

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