Bathroom Extractor Fan

[Gos1]

Hi. Just installed one of the above. Works to some degree, only problem is even though it's a quiet one, where i have installed the fan is directly under a bedroom, and unfortunately i can hear a hum! Not a problem during the day but in dead of night if some one has a shower and switchs on the light, this may cause a problem. Was wondering if there is some thing i can do, like maybe mount the fan into the eves outside. PS is there a limit to length of ducting between the inlet and the fan? As if what i asked was possible then the ducting run would be approx 1.5metres. Cheers in advance.

 

[wingcoax]

Even mounting the fan outside wouldnt make it much quieter. Most of the hum will be from vibration in ducting.

 

[Gos1]

Thanks i checked, whilst the fan unit is on by holding it most of the vibration/hum comes from the unit.

 

[ColJack]

is it a surface mounted thing or an inline ducted one?

if it's the latter, try using flexible conections to it and suspending it from string or cables... mount on AV mounts or any other means of isolating it from the building structure..

 

[Gos1]

Good One . It is a inline ducted one.
Next question what flexible connections would be recommended?
It's sunday and i'm heat stroked

 

[RF Lighting]

Flexi duct

 

[Gos1]

Maybe read the entire question

 

[RF Lighting]

Coljack said to you

try using flexible conections

You asked

Next question what flexible connections would be recommended?

I told you

Flexi duct

Which bit of the question have I not read?

 

[Gos1]

The "flexible connections" in question are of which to support the fan unit away from the joist, thus hopefully reducing the hum, which maybe a problem at night!!!!

 

[ColJack]

no, the flexible connections are what RF said, flexible ducting, thus isolating the ducting from the fan.. removing one possible path for sound conduction..

you mean what AV mounts?

rubber av mounts are available, or av foam or spring av's and so on..

 

[galco]

If vibration / noise is a problem and fitted for general ventilation rather than to solve condensation / mould problem try fitting a capacitor inline to reduce voltage to the unit - hence making it run slightly slower than at full speed.

 

[ColJack]

what twaddle, a capacitor does nothing to reduce voltage..

 

[galco]

I take that twaddle and double it.
Have you tried it?
Take one in line duct fan - connect with a capacitor such as one 2μF capacitor http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3779018 and voila a motor that runs slower and quietly! Changing capacitor value changes the reduction in motor speed and noise.

 

[ColJack]

it does nothing for the voltage, I never said it doesn't affect the speed..
it shifts the current out of phase with the voltage..
this means that the "power wave" is effectively double the frequency but a lower peak..