Can I still use a covered extractor fan?

johnny_c

I have a bathroom extractor fan connected to the light pull. The wind that comes through it is terrible, so I have covered it with a stretchy silicone rubber lid! It works a treat, but is there any danger in operating the fan whilst it is covered/ blocked? I can't expect the family to remove and replace the lid every time they put the light/ fan on. Thanks

Jeepers_Creepers

Unlikely, but I guess possible slight risk of fan overheating if left running for a longish time - it won't be getting a cooling flow of air. I suspect you've noticed that it's running at a faster rate too as it doesn't have to push air?

You can get anti-draught backflaps you can fit in the ducting.

Myser

It isn't ideal.  You could just replace the fan with one incorporating an automatic shutter like this range:

https://www.airflow.com/product/icon-range/

johnny_c

I suspect you've noticed that it's running at a faster rate too as it doesn't have to push

Surprisingly no. It appears no noisier, nor runs faster with the lid on . 

Jeepers_Creepers

johnny_c said:

I suspect you've noticed that it's running at a faster rate too as it doesn't have to push

Surprisingly no. It appears no noisier, nor runs faster with the lid on . 

I wouldn't expect it to be noisier - especially as you are covering a sound-escape hole - but would have thought it would be spinning faster as far less drag. It might not be enough to be noticeable tho'.

(Next time you are vacuuming with a 'nozzle', try covering the inlet - listen to the motor react. Don't do this in your dressing gown, tho'...)

Myser's suggestions are almost certainly the best way to go.

Mutton_Geoff

johnny_c said:

I have a bathroom extractor fan connected to the light pull. The wind that comes through it is terrible, so I have covered it with a stretchy silicone rubber lid! It works a treat, but is there any danger in operating the fan whilst it is covered/ blocked? I can't expect the family to remove and replace the lid every time they put the light/ fan on. Thanks

Are you in a rented property or do you own it? Very risky reducing ventilation in a bathroom, expect damp issues to be along shortly. Better to replace with the icon model (I use them all the time).

Descrabled

Fan speed

I would expect the fan to run at very nearly 50 Hz (or a multiple) as there will be so little drag once the fan has reached full speed.

Similarly the electrical wind turbines always run at constant speed regardless of the wind speed. The amount of power varies with the quantity of air passing through the blades. The fan or turbine speed is determined by the speed control on the very large (nuclear) generators.

I stand ready to be corrected.

Mutton_Geoff

Descrabled said:

Fan speed

I would expect the fan to run at very nearly 50 Hz (or a multiple) as there will be so little drag once the fan has reached full speed.

Similarly the electrical wind turbines always run at constant speed regardless of the wind speed. The amount of power varies with the quantity of air passing through the blades. The fan or turbine speed is determined by the speed control on the very large (nuclear) generators.

I stand ready to be corrected.

I thought wind turbines had variable pitch blades where different power is obtained from constant rotational rate (same as a variable pitch propellor on an aircraft). 50Hz is a frequency, not a rotational speed as such, the shaft will spin at a speed determined by the motor manufacturer, not the frequency of the a/c supply into the (squirrel cage) motor.

Wind turbines don't use nuclear generators, that is a different source of energy. None of the above applies to a cheap extractor fan with plastic blades that is throttled by blocking up the inlet. Expect the noise level to rise due to turbulence over the now stalled blades and possibility of the motor failing or even catching fire due to lack of airflow cooling.

troffasky

That's why nuclear bathroom extractors never caught on, you have to leave them on 24/7 to make it worth the cost.

Mickey666

. . . and when they get to the end of their useful life they cost a fortune to dismantle

johnny_c

Thanks all. Not sure how it became about nuclear wind turbines.. but anyhow! 😃. To respond to many, I'm not renting , the bathroom does also have a window, and The icon seems better ( long term). I searched for ages for similar but never used the word 'shutter' ! I will investigate them.