Bungalow bathroom fan, no external walls

[timhoward]

I've just had a look at an extractor fan not working. As per title it's a bungalow and there are no external walls, so it vents through the loft and roof.
Earlier this year the customer requested a more powerful fan and the sparks fitted a Manrose inline unit. Fair play.

But the thing is, there's a vertical ducting run from the Manrose unit to the roof vent, and when I got there I emptied half a bucket of water from the vertical ducting and the fan.
I happened to see the neighbour who obligingly let me look at their setup, which was the original ceiling mounted fan and some heavily cladded ducting going straight up. I guess any condensation would simply fall down and through in that scenario.

Options as I see it are:
a) change it back to a ceiling fan and try and find some insulated ducting and reinstate a directly vertical run. Customer not keen as the fan location isn't above the bath and they wanted a better solution.
b) fit another Manrose unit, insulated ducting and presumably some kind of condensation trap.
c) Change to a very long horizontal pipe run through the bungalow side wall, this would be at least 6-7m of pipe.

I'm thinking a) as it's apparently worked for years before, but glad to hear any thoughts or previous experiences.

 

[snowhead]

Did the Manrose fan have a backdraught shutter or flaps on or in the ductwork?

The ducting in the loft should be insulated anyway but some if not all of the condensation you emptied out will be from when the duct was trying to act as a chimney without the fan to push the warm air out of the roof.

 

[timhoward]

No, very primitive and optimistic install…

 

[freddo]

Probably condensation, though on a referb we are doing at the moment a currently unused tile vent in the roof is defective and allows substantial amounts of water in when it rains. They are waiting for the roofers to replace it before the new ceiling is fitted. Worth a thought just in case.

 

[freddo]

Edit, I can't believe the effort they went to to fix the left side of the banding with 3 screws but failed to use insulated ducting in the cold roof space.

I tend to hang larger inline fans off loose large cable ties to stop the motor vibrating the ceiling, keeping the motor closer to the outlet vent than the ceiling also cuts down on noise in the bathroom

 

[littlespark]

is there an overhanging eave nearby that's closer than a gable wall?

fan mounted a little higher... suspended as Freddo suggests, with a solid duct downward slop... just a bit of flexy at the end

 

[buzzlightyear]

whats with the ducking behind the fixed one on the installation.

 

[timhoward]

whats with the ducking behind the fixed one on the installation.

I wondered if anyone would spot that!
It appears to be a section of the original ducting abandoned there.

 

[Pretty Mouth]

MF100, they're quite powerful fans. You can cover the fan unit itself with insulation to help reduce condensation (I have an email from Manrose confirming this).

I have done C), with a similar length of rigid duct (100mm plastic tube stuff), and it was still powerful, shifted the air nicely. You can lift the loft insulation and lay it over the top of the duct, again to reduce condensation.

Also have done B), again using rigid duct, with loft insulation fixed round the outside with cable ties.

For the same reason as @freddo , I prefer to fix the fan to the rafters (sometimes suspended via timber) rather than the ceiling joists, to prevent vibration. Very short lengths of flexi duct, connecting the in/outlets of the fan to the rigid ducting also prevents the vibrations transfering to the rigid duct.

 

[Mike Johnson]

Surely the point of a bathroom extract is to take out the condensation in the room and the fan being powerful enough to move the condensation to another area, the problem as I see it is the corrugated ducting moist ladened air will deposit water droplets onto the corrugations and are then sheltered by them, smooth ducting would prevent this, IMO insulation around the ducting and fan is to reduce noise.

 

[Midwest]

If you use solid ducting, you can use these;

Condensation Trap for 4 Inch Soil Pipe | Manrose (1440 / MONV434)

www.tlc-direct.co.uk

Or has somebody mentioned that..

 

[suffolkspark]

@timhoward maybe originally it had a pasivent fitted, which were just a grille with a flap which opened with steam and went straight up in insulated duct, no electric. ive lived somewhere with those before.

If you really cant get to a soffit or out the gable maybe move the fan to be closer to the roof, fixed to truss so its only got a short exhaust, so the inlet side drops away back straight to the grille, at least then it will drip back out the grille and not collect in the motor, insulated duct.

Or theres the inserts you can fit inline that drain away condensation, but youd need somewhere to run it

 

[Pretty Mouth]

If you use solid ducting, you can use these;

Condensation Trap for 4 Inch Soil Pipe | Manrose (1440 / MONV434)

www.tlc-direct.co.uk

Or has somebody mentioned that..

Some of these are designed for 100mm ducting, some for 110mm soil pipe. However, you often find the 110mm traps being sold as being 4 inch, or 100mm. Very annoying when you come to do the job and it doesn't fit the 100mm duct you bought (often from the same supplier)!

IIRC the condensation traps that toolstation sell are for 100mm ducting.

 

[Midwest]

Some of these are designed for 100mm ducting, some for 110mm soil pipe. However, you often find the 110mm traps being sold as being 4 inch, or 100mm. Very annoying when you come to do the job and it doesn't fit the 100mm duct you bought (often from the same supplier)!

IIRC the condensation traps that toolstation sell are for 100mm ducting.

Sorry bad example link, but as you said 100mm are available. Just need to pipe the condensation to somewhere.

 

[Mike Johnson]

You could link the condensation trap back to the shower grill to drip into the shower, when the fan is on it should not drip, but will then drain away through the shower tray once the fan is off.