Am I expecting too much- Manrose 100T inline extractor fan?

[piper64]

I've just fitted a Manrose 100T extractor fan in my loft space to vent the bathroom which was like a wet room after a shower.

First, considering the cost and alledged ability, I'm not overly impressed by the clearance of condensation on the tiled walls and elsewhere, especially as I searched for a quiet, efficient fan and was advised by the local supplier to get this due to it's ability to move a lot of air.

I'm currently using flexi duct, as advised by the supplier, but now see that rigid pipe could be better. I've kept the flexi as short as possible, avoiding bunching up the coils and bends in the pipe.

Is aluminium flexi any better?

If I go the rigid pipe route, do I need to seal the joins or are they a tight enough fit as is?

Thanks.

 

[Plumbkinobi]

Hi, I havnt googled it yet, what's the total air extraction per hour on that unit? Most 4inch extractors are fairly underwhelming

 

[Agile]

Most have a very small actual air flow.

But the specs are usually useless because they are free flow WITHOUT any ducting.

The flex duct has rough walls which restrict flow compared with rigid duct.

But the worst cause is that most people expect to exhaust air without considering how it is to be replaced!

Tony

 

[Plumbkinobi]

Agree with agile, (hi agile long time no see) if the room is air tight then the extractor is fighting against itself

 

[longdogs]

The best thing you can do is open a window.

 

[lbzbean]

I have one of these and it pushes a LOT of air through an 8m flexi duct (couldn't be any worse conditions), I take it you connected the high speed.

If you disconnect the extract end of the duct from the outside, how much air appears to be coming out?

 

[delmel]

What is the distance you are ducting, centrifugal fans perform much better over longer distance. Man rose are not fantastic, however it probably performs similar to many of the others. If you are around the 3 metres the one you have is probably never going to perform well. If you have a window, also open it as to take air out, you need air circulating in.

 

[piper64]

Thanks for the replies.
First to the moderator, I haven't duplicated my post. I posted in the 'wrong'section but was alerted to that by another member, so I posted in the 'correct' section.

There is a 1" gap under the bathroom door and the window is usually open on the latch too, so replacement air should be fine.

I've been out tonight to feel the air being pumped out of the grill and it's quite reasonable, so it would appear to be doing it's job. It's rated as 245m3/hr on high setting, which is how it is set from the factory. My dodgy maths tells me that the volume of air in my bathroom is 14.5m3, so this machine is capable of moving all that air in 3.5 minutes in scientific terms ie, no ducting.

The flexi ducting is around 2m altogether, but it sounds sensible that rigid ducting would be less hinderance to airflow.

 

[JohnD]

it will work better with the window closed.

 

[vulcancontinental]

We have a 'built in' shower so a cubicle floor to ceiling with a simple curtain across. Discovered that the extract in the ceiling with curtain closed after a shower is the best thing. Absolutely no mould and window open all the time.

 

[stem]

Am I expecting too much?

According to the spec, the performance of the Manrose 100T is 85m3 per hour. In reality, as already said, it will probably be a bit less due to resistance or the duct, grille etc., so even if it was only managing 60m3, that is still 4 changes of air per hour, which should be sufficient to clear the room of the initial steam and much of the added moisture which continues to be released into the room after you have finished showering as the walls / floor towels etc., dry. Does it run on long enough after showering?

I'm not overly impressed by the clearance of condensation on the tiled walls and elsewhere.

I've yet to come across a fan capable of sucking condensation off walls So this is where warmth comes in. Warm air will evaporate the moisture and collect it. Only once that has happened and the moisture is airborne, can it be sucked out by the fan. If the room or walls are cold, then it will take much longer for them to loose their moisture to the air. This tends to be a problem in homes that are not heated for long enough periods to allow the structure of the building to warm up, or older properties with uninsulated walls.

Finally as has been mentioned, there must be a free flow of air across the room. When the fan draws air out of the room, usually the replacement air comes in from the door. Ideally the two points should be diagonally opposite each other so that the air flow crosses the entire room, or as much of it as possible. Mounting a fan close to the point where the air comes in creates a 'short circuit' and will mean that only part of the room is properly ventilated.

 

[lbzbean]

The MF100T is 245 m3/hr

Mine is really powerful, you can feel the draught under the bathroom door on the back of your feet.

 

[Agile]

245 l/hr would be hardly noticeable.

One of the problems of many fans is that they are linked to the light and only have an over run of about 10 min which is totally inadequate to clear condensation.

The ones with a humidity switch are far more satisfactory.

But as mentioned above adequate heat needs to be available to evaporate the condensed water.

Tony

 

[JohnD]

we are presuming that you mean MF100T which is quite powerful

http://manrose.com/specifications/mixflorange.pdf

however if you mean LW100T it is pathetically weak.

http://www.manrose.co.uk/specifications/lowattrange.pdf

 

[piper64]

agile, johnD it is the MF100T, so should be good at 245m3 /hr......not l/hr... and it's set to run on for around 20 minutes.

stem, I see what you mean about sucking condensation of the walls, but they are ceiling to floor in tiles which I hate as they are so cold regardless of room temperature. Next project.....

vulcan, the shower curtain is always left closed after a shower at the request of the Mrs, even before the fan was fitted.

ibzbean, I've tried standing by the door and not getting the same draught as you seem to be getting from yours with the window close or open.

Well, it seems I'm doing all the right things and it does clear the air quicker than without it. Otherwise I'm looking at installing a vaccum cleaner.

Thanks all.