Bathroom Fan Ventilation changes

Discussion in 'Plumbing and Central Heating' started by shaky1105, 22 May 2021.

  1. shaky1105

    shaky1105

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    Hi, dunno if this is the correct forum to ask this but I am changing my bathroom around totally to how it used to be and I was wondering what the best way to alter the extraction setup would be.

    Currently, there is one vent hole in the ceiling, about 500mm away from where the old bath used to be. This runs straight up into the loft through about 400mm of insulated rigid ducting, through a 90° bend and into a Manrose MF125T fan set for a 12 minute overun, then roughly 6M of insulated rigid ducting (with a fall of about 100mm) to a gravity shuttered opening in the gable end.

    Currently this works perfectly, extracts the steam from baths/showers great and the ductwork is always dry.

    I have extended the bathroom by about 1M and am going to fit a separate walk-in shower at the opposite end to the new bath. The glass panel will only be 200mm from the ceiling so I should imagine the steam from a shower will be concentrated in that area.

    Looking at parts that are available, I was thinking of moving the fan unit slightly over one way, fitting a Y-Piece to connect to the existing ceiling outlet and then running approx 1.6M of fresh rigid duct to another ceiling outlet above the shower. Does this setup sound like it will work OK ?

    Also, is there an effective way of cutting down the noise the fan makes ? I'm guessing it's the actual airflow which is causing the most noise as the fan itself can hardly be heard at all when there's no ducting connected. I was wondering about not letting the actual ductwork physically touch the fan body (by using 50mm wide neoprene tape and supporting the ductwork separately) but I'm prepared to put up with the noise if it means the extraction rate is still good.

    Finally, can an electrically operated louvre shutter be fitted to this setup that would open/close automatically dependent on the fan running as when the wind is blowing and the fan isn't running the shutter rattles like buggery, to the point of almost waking us up some nights.

    TIA
     
  2. JohnD

    JohnD

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    Manrose showers are IMO quite poor quality and annoyingly loud, though the Manrose MF125T fan should be one of their better ones.

    you can get better fans now from other makers, with ball-bearing motors, quiet design, and resilient rubber mounts, and can also be more powerful. A steamy shower needs a powerful extractor. Some of them have an integral butterfly valve to prevent backdraught, in a less noisy plastic. For your on-the-wall vent, I recommend the cowl type which has a protective hood, and just one large flap that is not very rattly. You can buy a one-way flap to go inside the duct, away from gusts of wind outdoors, and you can wrap the duct in mineral wool or something to muffle noise.

    What size is your duct? You can get inline fans to fit 100mm or larger.

    You might also consider an extra-powerful extractor over the shower, and a less powerful one for other purposes.
     
    Last edited: 23 May 2021
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  4. shaky1105

    shaky1105

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    I'm surprised you saying they're loud John coz without the ducting connected it's virtually silent ! I honestly thought 90% of the noise I was experiencing was from the actual airflow through the ductwork. :unsure:

    According to the spec sheet, the one I've got has got a ball-bearing motor, although admittedly it is completely plastic with no feet, including the frame. The best part about it is the motor unit can be detached separately from the frame and ductwork for cleaning. It's supposed to have a rate of 310M³ p.h. which I thought would be ample for my 3.2 x 2 x 2.4M bathroom. It certainly seems to work OK atm.

    Maybe I should consider investing in a larger, more powerful model. I originally thought the MF125T I had would be sufficient but would there be any point in fitting a 150mm model and use reducers to fit my 125mm ducting or would that be defeating the object ?

    That's something that would be easy enough to do for certain. I have a kitchen hood extractor setup with an in-duct backdraught shutter (but no shuttered outlet vent) but that is a bit rattly as well, although that is a MUCH shorter duct so I presume that is the problem there. The good thing about that is we can't hear that one as the kitchen is at the far end of the house, so not a problem as such. I already have all the ductwork insulated with wrapped loft insulation, covered with that silver foil bubble-wrap type stuff and all the joints are silver foil taped to help with condensation.

    The ductwork is 125mm throughout, to match the MF125T inline fan unit. :D

    I'm trying to avoid having separate fans to save on the wiring/switches as I've got all the switches/wiring completed in the hallway and it's just about finished. It's not impossible but I'd rather not have to faff about installing more cabling if I can help it and I don't want any pull-switches in the bathroom as I hate them with a vengeance :LOL:

    Thanks for all the pointers John, you've given me some food for thought
     
  5. JohnD

    JohnD

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    310 cu.m hr is pretty good and should be adequate, even for a steamy shower.

    Water vapour is lighter than air so will naturally rise towards the ceiling and your timer model will help to clear the room after your shower. If necessary you can lengthen the delay. Some people with noisy fans grumble about the noise.

    BTW you are not obliged to have pull switches. You can use wall switches as long as they are outside the zones and not going to get splashed, sprayed or dripped on.
     
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  7. shaky1105

    shaky1105

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    I'm glad about that as I spent quite a long time a few years ago when I originally bought the fan, researching the best one to get (y)

    Like me you mean ? :LOL::LOL::LOL: Tbh John, like I said earlier, I'll put up with the noise as the fan appears to be doing it's job. I was just trying to explore any other methods for possibly reducing the volume without affecting the performance too much and also checking that my idea of two duct runs (one above the shower and one above the bath) would still work with this fan model. Not physically attaching the ductwork to the fan body has definitely reduced the roar volume (albeit not by that much) so I think I'll carry-on down that route using neoprene tape as well as your idea of swapping-out the external vent to a cowl type and see how I go.

    Unfortunately that is something I haven't got the pleasure of (out of zones) because of the layout of the bathroom. I have a zoned central heating system, using 240v switching and I'm having to use a remote sensor in the bathroom as I haven't got anywhere out of zone to fit a thermostat :(. Saying that, the remote sensor works fine but I did have to use shielded, twisted cable as it runs fairly close to a lot of the cabling running through to the kitchen (unavoidable) and I was getting induced voltages of about 8v to 9v a.c and it was sending the thermostat nuts :LOL:. All sorted now though (y).

    Thanks again John. :D
     
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