Shower extractor fan and ductinge

[traveller2311]

Hi
Can someone help me please. We have just moved into a house with a shower room in the middle of the house downstairs. I need to fit a fan for extraction. It has ceiliing fan at present but I don't think its doing a good job. The ducting is about 10m long which runs into the loft and out to the soffit. I need to know what is best way to extract with the distance involved will a normal centrifugal fan do or am better of with a inline fan if so where do I fit it distance wise. I need some think with a timer also.
Thanks

 

[Taylortwocities]

Absolutely a timer - probably 15 minutes.

You'll need a beefy fan to push up 10m of ducting. You don't say what size duct you have - I guess its 100mm?

Most cheaper 100mm fans are only good enough to push air through a 9" wall so be prepared to stump up some cash to get effective air throughput.

This table http://www.tlc-direct.co.uk/Technical/DataSheets/Manrose/MRK.htm will give you an idea but you'll see how air throughput decreases with duct length (especially corrogated ducting).

The other factor is your bathroom door. If it is well-fitting then your fan is trying to create a vacuum in the shower room. You have to let air in so the steam can be vented out. You'll improve things by cutting a hole in the door/wall with a diameter at least as big as your fan.

So, you'll need a fan like this http://www.tlc-direct.co.uk/Products/MRMRK100M.html plus a timer module.

 

[TicklyT]

Centrifugal fans can usually create higher pressure differentials (thus higher flows through more resistive ducting) than axial ones, but an axial flow may win out with free flowing ducts.

Rigid ducting makes for a better airflow than the typical flexible ducting supplied with fan kits.

As above, sufficient ventilation to allow replacement air into the room is necessary. No need for a big hole through the door - a 1/2" clear gap at the bottom of the average door is usually enough.

 

[traveller2311]

I have the PVC flexible ducting, half way then PVC tubing and then PVC ducting again. There are a few bends involved in this ducting also. The fan that Taylortwocities has shown, I assume it has to postioned about half way of the ducting and then just a grille in the shower room where the old fan is it at present.

I have also the upstairs bathroom to sort out, again no windows but ducting going into the loft can i join the two ducts together to make one outlet and have one fan up there is there anything that will do the job. I really want to tidy up what the previous owner did which looks like a real cowboy job!

Thanks for all the advice.

 

[Taylortwocities]

Putting the fan half-way will help.

If you have two rooms to vent then you could do it with one fan, but remeber that both rooms will be vented at the same time & you need to sort out special switching controls.

If you use two fans then you'll need to arrange backdraft flaps so that smelly/steamy air from room 1 does not get pumped into room 2

There's a guide here
https://www.hvacquick.com/howtos/howto_multiple.php

 

[traveller2311]

I think I will use the the fan from TLC http://www.tlc-direct.co.uk/Products/MRMRK100M.html to extract for both bathrooms with backdraft flaps as you say. I have found a timer http://www.tlc-direct.co.uk/Products/BGDT20.html which looks like it will do the job, now to get someone to wire it up for me so that the fan comes on individually in each bathroom.