Shower ceiling fan (with run-on timer) and Built-in LED light

[DaveyH]

Hi,

We want to install a ceiling extractor fan (with a run on timer) and built in LED light directly over our shower cubicle.

The actual fan will be in the loft (screwed to a joist or rafter) and will be vented outside through either a tile vent or soffit vent via flexible ducting.

I was going to buy one of these kits.

http://www.screwfix.com/p/manrose-in-line-led-shower-light-fan-kit-bright-chrome-mm/45818

However, when I've put our bathroom dimensions (2.5m x 2.1m and 2.42m high) into this online calculator https://www.tlc-direct.co.uk/Technical/Ventilation/Ventilation4.html

The fan is nowhere near powerful enough (it only shifts 83 cubic meters per hour, but the calculator say we need one capable of 254 cubic meters per hour). Here is a screen print.




Are there more powerful kits available? If so, where do you get them from? Or is that calculator a bit over the top and that kit will actually be fine? I would only class our bathroom as small to medium sized. Or maybe I'm just not using the calculator correctly.


Background notes.

The house is fully 17th edition, part P (RCDs and MCBs on the consumer unit etc).

The ceiling is 242cm above the floor, so 17cm above the 225cm above shower Zone 1.

The fan isolation switch will be located outside of the bathroom and the shower light switch will also be located outside of the bathroom (both several meters away from any bathroom zones).

Thanks in advance

 

[JohnW2]

The fan is nowhere near powerful enough (it only shifts 83 cubic meters per hour, but the calculator say we need one capable of 254 cubic meters per hour). Here is a screen print.

That calculator is assuming that you need 20 complete air changes per hour (254 m³/hour for a 12.7 m³ room). You may, or may not, want/need that amount of extraction. If you want further 'opinions', I'm sure that there are plenty of other calculators you could find on-line.

Kind Regards, John

 

[ban-all-sheds]

By the time you factor in all the losses from ducting, intake and outlet grilles, pressure drop in the room, and the woefully inadequate level of changes per hour required by Building Regulations etc, you will realise that the old adage needs modifying:

Lies, damn lies, and fan calculators.

Unless you are fussy about a bit of noise, then until you get to the point where animals and small children can get pinned to the intake, it isn't really possible to have a fan which is too powerful. Jolly easy though to get one which is too feeble.

 

[flameport]

HAre there more powerful kits available? If so, where do you get them from?

Many places, including the same website with the fan calculator:
https://www.tlc-direct.co.uk/Main_Index/Ventilation_Index/index.html

 

[JohnW2]

Unless you are fussy about a bit of noise, then until you get to the point where animals and small children can get pinned to the intake, it isn't really possible to have a fan which is too powerful.

That's all very well but, if the fan is going to be on for appreciable periods of time, surely even 254 m³/hour, let alone a lot more, could represent a tremendous loss of heat (at least, during winter), which could presumably have substantial cost implications, couldn't it?

Kind Regards, John

 

[ban-all-sheds]

More or less than the cost implications of condensation, mould, and mould spores?

 

[JohnW2]

More or less than the cost implications of condensation, mould, and mould spores?

One might hope that there would be a method of addressing the latter which was better/cheaper than pumping hundreds of cubic metres of expensively-heated air into the winter atmosphere!

Kind Regards, John

 

[ban-all-sheds]

Yup - whole house ventilation with heat recovery.