Condensation on bathroom extractor fan?

Pulsedriver

Pulsedriver

Pulsedriver

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Hey folks, today I changed the ceiling extraction fan to a more powerful in line fan, the previous one was also an in line fan but about half as powerful according to the tech sheet.

I re used the vent hoses as the loft is boarded and didn't fancy taking boards up to change the pipe.

Anyhow, I attached the pipes correctly in the loft, and added a "back draught shutter" to the pipework to stop the air flowing back from outside and keeping it one way flow only.

Tried it all out tonight and noticed that it's got a lot of water drops around the ceiling vent and the room isn't exactly any better than it was before changing the fan, in fact the previous fan didn't have the water droplets on it.

Just trying to figure out the best solution for it, would upgrading the in linr fan cause that alone ? Is the backdraught shutter a potential issue? They are the 2 differences from the previous setup ...

Thanks in advance.
 
Stupid question is the back draft shutter in the right way? What was the power difference bettween the two a back draft shutter could have absorbed it? How long is the over run and how easy is it for air to get into the bathroom? You can have the most powerful fan in the world but if the bathroom door and window seal well it will make no difference!
 
Perhaps it is drawing in more moist air and that is now condensating inside the pipe work?

Did the previous fan allow for an drops in the pipe where water could sit and prevent it from running back down and dripping?
 
Old fan = 85 meters cubed per hr extraction rate
New fan = 245 meters cubed per hr extraction rate

Pipe work is the same although the only difference is the mounting, this is the old one which was mounted on the joist bit;

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New one floor mounted (with anti vibration mat)

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Wondered if I should lag the pipe somehow to prevent it getting cold in the loft?
 
Yeah I'd wrap some insulation around it (eg standard loft insulation) and might solve it.

It will be due to warm moist air condensing on the first cold surface it touches (ie the un lagged duct)
 
I changed from/to the same one (actually looks identical to your new one) and haven't noticed anything wet or dripping from the grille above the shower - is that the bit you mean as you said 'fan'? Or do you mean the fan bit in the loft is getting wet?
 
Sorry Duke I meant the grille above the shower area.

Thanks for the suggestions folks, I went up in the loft tonight and removed the backdraught shutter, and also used some spare loft insulation to cover the pipes both exit side and entry side, I also timed the over-run when the light is turned off, and it's about 2 minutes, so I think i'll have to increase that, it's difficult to gauge as the fan itself has an adjustment on the unit, but does not have any indication of minutes, so if you turn it a bit, it could increase it another 5 mins etc!
Had a shower so will check later if there is any condensation...
 
It's possible due to the increased performance that you are now extracting moist air from the wider house hence more condensation as it is doing more work.

Your old one may not have been working properly as well either, so there was no water condensing around the fan grill skewing your reference baseline perception.

Or it is just a badly installed (looks ok from pics) / faulty unit.
 
Hey folks so an update is since covering the pipes with insulation and removing the backdraught shutter it has massively reduced the condensation which is good.

I think there needs to be some more air flow in the bathroom as the door, when opened after you can feel a flow of air coming in, so perhaps need to plane the bottom of the door to get a bit more flow ?
 
I installed a wide but narrow air vent in my bathroom door so that the fan can pull (dry) air into the room. Not sure if taking some off the door would do the same thing. (maybe /maybe not) but for sure air needs to come in from outside the room with ease.
 
gEd said:
I installed a wide but narrow air vent in my bathroom door so that the fan can pull (dry) air into the room. Not sure if taking some off the door would do the same thing. (maybe /maybe not) but for sure air needs to come in from outside the room with ease.
Click to expand...

This would be better than my option I think! Will go with the vent idea! :)
 
Pulsedriver said:
Hey folks so an update is since covering the pipes with insulation and removing the backdraught shutter it has massively reduced the condensation which is good
Click to expand...
which do you think is most responsible - I don't have a backdraught and probably loose heat through it, which would keep piping warm and reduce condensation ... or is the backdraught inhibiting flow ?

...opening window as opposed to sucking heat from house is more economic ?
 
jpaul said:
which do you think is most responsible - I don't have a backdraught and probably loose heat through it, which would keep piping warm and reduce condensation ... or is the backdraught inhibiting flow ?

...opening window as opposed to sucking heat from house is more economic ?
Click to expand...

I think the backdraught shutter is good but it seemed very sensitive to air flow, so there is a chance it was only half-opening, I agree about the window opening, but it has to be said, the bathroom window has a really stiff handle, and to close it almost feels like you'll snap the handle off, I can't see doing it every day being very good, ideally i'd get that fixed, but to be honest the window (and the rest of the house windows) are in need of replacing, but like everything with house ownership, it's finding the £££ lol
 
Felix said:
and no ugly vent in your door.
Click to expand...

A bathroom (with a closed door) is a bit like a PC case. just substitute damp air for hot air.
You need dry (cool) air coming in and wet (hot) air going out and with minimum pressure drop so that the fan(s) can work effectively. Therefore it is important that the "box" has adequate airflow.
Clearly if the room were 100% airtight, the fan would not be able to do it's job so there's a consideration as to the power of the fan and the ease with which air can enter the room. I would have thought that the fan manufacturer would have something to say on this point in their installation guide.
 
I just take 10mm off the bottom of the door. You want the airflow to be as far away from the extraction point as possible, chances are that's the bottom of the door. Top of the window won't be as effective. If your worried about loosing heat use a heat recovery system and place the other vent on the landing outside the bathroom.
 
gEd said:
A bathroom (with a closed door) is a bit like a PC case. just substitute damp air for hot air.
You need dry (cool) air coming in and wet (hot) air going out and with minimum pressure drop so that the fan(s) can work effectively. Therefore it is important that the "box" has adequate airflow.
Clearly if the room were 100% airtight, the fan would not be able to do it's job so there's a consideration as to the power of the fan and the ease with which air can enter the room. I would have thought that the fan manufacturer would have something to say on this point in their installation guide.
Click to expand...

Trickle vent on the window and the gap under the door (and around the door as its not air tight) should be enough, no need to start cutting holes in them.
 
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