Bathroom extractor fan advice

[Adam Funk]

In 2016 we had an S&P SLTD250SILENT fan installed in the bathroom, wired to the fast side only and connected to the light switch through a Manrose humidity/timer controller.

It doesn't seem to be clearing the humidity out very well any more. I stuck my head and arms through the hatch, disconnected it at both ends, and checked a few things. The impeller is definitely turning when it's on, and there are no blockages in the flexible ducts (the one coming up from the grate has a sharp bend around a beam but always has). I vacuumed everything out as well as possible in the awkward position and reassembled it.

Do these things wear out over time? Any recommendations for a replacement?

Thanks

[ARW]

I would suggest the Manrose unit needs a tweak.

[alan_m]

Maybe the sensor has been incorrectly driven and has "drifted"

Big Clive video

[Animal]

The reason it's not very effective is it's a 4" fan.

[alan_m]

The OP suggests that the same set-up did work satisfactory at one time.

Perhaps something in the rest of the house has changed and the "replacement" air is more water laden?

[Adam Funk]

I just checked --- it's set for about 40% (the markings go down to 50,

40, ON) and 30 minutes (after the light is switched off). I don't know about the reliability of the humidity detector but would you expect to clear a small bathroom adequately in half an hour?

[Adam Funk]

Isn't that the standard size for bathroom extractor fans?

I can't think of anything. We're in the habit of leaving the bathroom window locked in the slightly open position until all the condensation disappears anyway --- it just takes longer than it used to.

[The Natural Philosopher]

mostly, yes

[fred]

Its not just the size of the fan that is important. Extraction is also. 4" flexible pipe is a killer even if it gets a straight run and it doesn't exit on the upwind side of the house

[Andrew]

But is the fan running the whole time (it claims to be silent) ?

Have you made other changes like a new shower system that is creating more steam ?

I just open the casement window a few inches and after 15 mins or so all the steam/condensation has gone.

If the extract duct is close to the window anyway then isn't outside air just going to be sucked in and expelled ?.

[Animal]

Yes 4" fans vary, but they tend to be pitiful. The quieter the less effective.

40% RH target is far too low. 60 or 65% is normally fine. Long pipe runs, wiggly bendable tube & any other obstructions badly affect performance, especially with axial fans. You might have a mild leak loading the air with water vapour, or fan bearings might be getting stiff, slowing it down. As folk said, a window that can lock a fraction open works as well, but without energy use or fire risk.

[ARW]

It might just be the time of year with more moisture in the rest of the house - even more people in the house for longer etc

Or maybe it just seems to take longer or people are having longer hotter showers.

[Adam Funk]

It's just audible --- if I'm listening for it without the shower, toilet, or taps running at the same time. And if I hold a piece of toilet paper up to the grate it sticks.

Nothing has changed inside the bathroom since the fan was installed. The grate is in the middle of the ceiling. The window is in the middle of one end wall and the door (kept closed with a spring closer) is in the middle of the other end.

[Adam Funk]

Well, I haven't been taking any scientific measurements, but it seems to have been more of a problem, seasonally adjusted, over the past couple of years than before.

[Tim Lamb]

Any chance the vent flaps are not opening (should be visible from outside) or a non return valve is not functioning properly?