Bathroom Extractor Fan Dripping

[jamesw27]

I have a small a bathroom with a 4 inch axial fan which broke. When replacing it was noticed that the flexi ducting didn't go anywhere and was just vented into the attic and I was advised to vent it outside via the roof. 

The roofer recommended made a vent through the roof and replaced the pipe with a solid plastic 100mm soil pipe. Now during showering the fan seems to collect water on the outsides which I'm assuming is condensation running back down or not making it up through the fan ?

I've tried lagging the pipe with aluminium foil and sheep wool but it's still happening. Since it's collecting drops during the shower I'm unsure whether it's a power issue although I can't remember the old one doing that and this one is a higher powered fan (may be now the weather is cold) ...

Would really appreciate any support / advice and have included some images below for reference.

https://ibb.co/MgwkRbS
https://ibb.co/1vLLtQf

 

[Murdoch]

those links don't work.

 

[jamesw27]

https://imgur.com/s3SzQAL

 

Do these work ?

 

[Murdoch]

Yes.

So I suspect your problem is that the hot air is condensing and running back down in to the fan - which will almost certainly trip the circuit when enough collects in the cover!

There are "condensation" traps available - not sure exactly what they are called 

 

[Evans Electric]

How long is the fan running for ?    I presume the overrun is  working  ?      You need the full overrun time  working . 

Can you compare the  efficiency of your fan  to other  100mm  ones .  ?     The "Silent "  feature may reduce efficiency .   

 

[jamesw27]

Thanks both. Is a condensation trap easy to retrospectively fit ?

Fan is rather short only about 16 / 17 inches. The new fan a actually has a higher extraction rate than the pervious and the overrun is set to 30 mins.

 

[Murdoch]

this is what you need:

https://www.tlc-direct.co.uk/Products/BGCT4.html

But then you need somewhere for the condensation to drain to .....

 

[jamesw27]

That makes sense. I'll take a look in the loft tomorrow and see how easy it would be to find somewhere to run that off too 

If I'm going to tamper with the pipe to install  a condensation trap (assuming the way is the saw a section off and then fit it in the middle ... maybe it's worth fitting a backdraught shutter too as when it's windy I sometimes see the fans spinning too ?

 

[Murdoch]

maybe it's worth fitting a back draught shutter too as when it's windy I sometimes see the fans spinning too ?

I wouldn't - bathrooms / homes need to breath

 

[Sharpend]

A condensation trap on a vertical pipe will not work, water will run down hill better than running horizontally? 
ideally you need to come off the fan at an angle and insert a trap on the pipe running down to the wall plate then either to a soffit or if not available drill out through brick, cut end of drain pipe at a 45° longest point at top to stop rain finding it’s way in. 

 

[Geoff1946]

You could use flexible ducting and make a loop in it but I don't know if you may then get condensation building up in the loop. 

On my bathroom I used an in-line fan suspended from the rafters and flexible duct which exits via the soffit.

 

[SPECIAL LOCATION]

I doubt that size of Axial fan is sufficient for the length of ducting and air it has got to push..

what extraction rate is it?    If its anywhere around 80 or 90m3/hr

it's too low IMHO..

better with a Centrifugal fan that can shift 200m3/hr or higher..

ALSO..

how big is the ventilation inlet that allows air to get into the room for you to extract out?

e.g. gap under door or similar..

If you don't have the same size aperture allowing air into the room any fan will struggle moving warm moist air out..

Most 4" axial fans are only good for a 12" duct straight through an external wall..

Guinness

 

[jamesw27]

Appreciate all the responses seems a few possible solutions. The fan extracts at 96/hour and I'd estimate the pipe is 15 inches without going up an measuring it. There is a gap under the door but met with carpet - perhaps I can try showering with the door open a tad tomorrow and see if that makes any difference as a temp solution.

Annoyingly I was told an inline fan wouldn't be suitable (should have asked why) as I did think that may be a better fit when replacing the old one.

Another option I considered was just moving the fan from the ceiling above the shower and putting it on the wall instead, although then I'd have to find a way to block the hole  

 

[jamesw27]

A condensation trap on a vertical pipe will not work, water will run down hill better than running horizontally? 
ideally you need to come off the fan at an angle and insert a trap on the pipe running down to the wall plate then either to a soffit or if not available drill out through brick, cut end of drain pipe at a 45° longest point at top to stop rain finding it’s way in. 

From the picture of the condensation trap shared by Murdoch I'd assume the water would run into the raised ridge around the sides and then subsequently through the run off or do you think because it's vertical that wouldn't work ?

 

[SPECIAL LOCATION]

There is a gap under the door but met with carpet - perhaps I can try showering with the door open a tad tomorrow and see if that makes any difference as a temp solution.

If you do the maths of the cm2 area of a 4" (100mm) diameter duct..

(Pi r2)   3.142*50*50 = 7855cm2

For an average 760mm wide internal door you need 10mm or gap 

7855/760 = 10.3mm

So no good having carpet blocking the airflow..

Otherwise its like trying to use a vacuum cleaner with a blocked outlet!!