Problem with bathroom extractor fan

[Elvistcb]

Hi, my niece lives in a flat and has a bathroom without a window. There is an extractor fan which packed up and an electrician installed a new one a few weeks ago. That then blew and he came back and said that the extractor wasn't fit for purpose as it is wasn't powerful enough to get rid of all the steam after a shower. he said that he would need to install a powerful device in the loft and just have the vent for it in the bathroom ceiling. The cost will be £990!! He also said that the new fan blew because it tried to suck out the steam and it wasn't powerful enough so the steam turned to water and flowed back down the vent and shorted the electrics! This sounds like nonsense to me! I think its more likely that as they have had a problem in the past of rainwater getting into the roof where the extractor goes through, its more likely that rain has got into the system that way.
Any advice or info would be appreciated.
thank you in advance

 

[brianmoooore]

How long is the ducting from the original fan to the outside vent grille?

 

[OLDBOY]

Not necessarily nonsense. It is a common problem at this time of the year for condensation to form in ducts from bathroom extractors. This is because the duct will be cold, it is after all direct to outside. Push a load of warm moisture laden air through it and it will immediately condense. I have had to remove a full bucket of water from a long horizontal duct in a roofspace before. In the case of a vertical duct all this condensation will run back in to the fan. 'Normal' axial fans are designed for short ducts straight through a wall, and are not powerful enough for long ducts. For this inline or centrifugal fans are required to create sufficient air pressure. It may well be that your electrician is correct and the best option is an inline fan and an alteration to the outlet and ducting, although this is not what you want to hear. I would advise getting other quotes for the work though.

 

[UNG]

You need a condensation trap fitting on the fan duct close to the fan

Had problems like this a number of times on one flat if the prevailing wind was in the same direction as the heavy rain the bathroom would get water in the fan and on the floor due to the height of the outlet and it's position on the building it was difficult to access it to change it fitted the condensation trap and connected it to the soil stack going through the loft and the problem was fixed this also fixed the pipe condensation running back to the fan due to the long duct run in the loft

 

[Elvistcb]

Thanks for your advice guys.

very helpful