bathroom extractor fan

[benpost]

i have a greenwood airvac ax100-b fan fitted in the bathroom which comes on when the light is switched on,however it does not seem to extract a lot of moisture as the bathroom steams up and things get wet (such as deodrant can). i took it off the wall and checked the pipe out of the flat is clear which is seems to be, except for some fluff around the edges.

so i'm guessing this fan isnt that great. ive looked it up and found its 140x152cm, 80m3 / hr free air , 230v~15w, 50hz. can i get a replacement which is more heavy duty as i need to do as much as poss to reduce condensation, due to mouldy walls etc.

thanks

[John]

Remember that to extract 80m3 of air then you need to provide for this to be replaced from somewhere. Just having a fan is only half the fix. Perhaps a grill in the door to allow dry air to enter might help (but even this air is not really "free")

[Owain]

If this is an axial fan and you are expelling the air into a duct, then you probably need to change it for a centrifugal fan.

Owain

[robgraham]

On the basis that your fan should in theory change the bathroom air in well under 30 minutes, unless it is really large bathroom (!), I do wonder whether your condensation problem could be due to poor insulation and regardless of how quickly you extract the air, the moisture is going to condense out onto the walls and ceiling.

I also wonder from your comment about the room steaming up which makes me think that perhaps you don't have any heating in there as I wouldn't have said that that occurs in either my shower room or bathroom which both have radiators. In fact the shower room has a humidistat fan, but the bathroom fan is hand operated and rarely do we use for anything but clearing smells - and that's in an old stone walled house. We did strip off all the lathe and plaster work and re- line with insulation.

Rob

[TheScullster]

"John" wrote

Also, the bathroom has to be warm enough to keep the water vapour in suspension. If the room is cold, the water will condense on the walls rather than taking the extractor fan route.

Phil

[benpost]

hi there is a radiator in the bathroom which is on quite frequently and warms it up nicely, its only a small bathroom the fan extracts air down quite a long tube to the outside of the flat, this tube is seen in the cupboard and bedrooms where it is boxed in at the ceiling/wall joint i'm not sure what you mean by axial and centrifugal fan can you tell me more? it just seems like this extractor fan isn't doing a lot.. even though it comes on and the exit path isnt blocked. there are no incoming vents for air on the door or anywhere else so that could be a problem? thanks

[John]

If there is no incoming air then you are attempting to create a vacuum - something that the fan can't do - but it can't suck air out if none is coming in to replace what is taken out.

Like you I am awaiting to read a justification on Centrifugal v axial. (Most fan heaters use a centrifugal (drum with blades))

[David Hansen]

On Mon, 10 Dec 2007 08:14:26 -0800 (PST) someone who may be benpost wrote this:-

"Quite a long tube" doesn't help much. How long is it? 1m, 5m, 10m? What is it made of? Oblong section plastic? Round section plastic? Flexible ducting? Metal?

Axial fans are not any good at blowing air along long ducts, as they don't develop a high enough pressure. Centrifugal fans are much better. This is explained well enough by the fan manufacturers, for example

addition to replacement air, insulation and heating, which was mentioned by others, there is another thing to consider, how the fan is operated. A humidity control sounds like it would be ideal, there are two models on the above page.

[TheScullster]

"benpost" wrote

If this long tube is of the corrugated type (and especially if there are bends involved) then you will be losing a LOT of the fans performance. For some good background check out the VentAxia site, particularly the knowledge centre and the system calculator. When you look at the parameters affecting ventilation calculations, you will understand better the short-falls of your own.........

i'm not sure what you mean by axial and centrifugal fan can you tell

This info will also be found at VentAxia site.

No commercial interest, I have bought both VA and Xpelair products for my home.

Phil

[The Medway Handyman]

Thanks for that link David - what a great information source.

[The Medway Handyman]

That is very important. Back in my high pressure cleaner days we had many customers who bought fixed hot water machines & installed them in sheds or enclosed buildings. They of course ignored the instruction book which clearly mentioned the need to allow air to come in. Result - oil fired boiler wouldn't ignite/run properly.

They would never believe it was their bloody fault, always blamed the machine.

[A.Lee]

I'll be in the market soon for a shower extractor fan - do they actually work? And are there any low voltage ones that you would recommend? Thanks Alan.

[benpost]

hi, the tube is round and is the length of one bedroom and cupboard so its about 4 metres at a guess. im thinking that the cause could be no air coming in to replace the air the fan is trying to extract... makes sense. so would fitting a vent on the bathroom door be the solution? or at least part of the solution, along with maybe a better fan?the current fan is greenwood airvac ax100-b i couldnt find a lot of info on google just a few sites selling it. thanks ben

[Paul Matthews]

Easy check, leave the door ajar,

[thelyricalterrapin]

Cut some off the bottom of the door so there is a gap of a couple cm there, like hotel bathrooms have.

Ke1th

[benpost]

hi,

leaving the door ajar seemed to help, the mirrors were still steamed up but there wasnt any wet on deodarant cans etc.

so i will be fitting a vent on the door or cutting some off the bottom.

the other thing i will look into is whether the fan is axial or centrifugal as a poster earlier mentioned.

thanks for all replies

[John]

Axial has the motor in the centre of the duct. (Imagine looking into the front of a jet engine)

[The Medway Handyman]

Most of the bathroom fans I see are like that - what does a centrifugal look like? Pickys on a site anywhere?

[Huge]

[benpost]

its definitely an axial fan i have fitted. so a combination of new centrifugal fan and a vent in the door should sort my problems out.

i did a quick search and found this fan

you think that would be worth getting?

thanks