ducting size question

[fullyabsorbent]

I need to extract 247 cubic metres per hour from my bathroom. I will be using a 150mm ceiling fan capable of extracting 250 m3/ph. Can you tell me which ducting system I should use for this? I have a 1.5 metre run. Currently I have 100mm circular flexible hose already installed, I intend to use a 150mm =96 100mm reducing spigot. Do you think this is sufficient or should I increase the hose diameter, to system 125 for example?

If I go larger than 100mm hose I will need to use rectangular flexible hose. It seems that the only rectangular flexible hose options are options available are =93system 125=94 (150mm x 70mm) or =93System

204=94 (204mm x 60mm). System 150 (180mm x 90mm) does not seem to be available as rectangular flexible hose. Is this correct and what do you recommend?

Many thanks for you help

[Steve Barker]

i'm not sure about your duct sizing, but i'm curious as to why you need to move so much air AND where is the replacement air coming from?

s

If I go larger than 100mm hose I will need to use rectangular flexible hose. It seems that the only rectangular flexible hose options are options available are ?system 125? (150mm x 70mm) or ?System

204? (204mm x 60mm). System 150 (180mm x 90mm) does not seem to be available as rectangular flexible hose. Is this correct and what do you recommend?

Many thanks for you help

[fullyabsorbent]

I have used a fan size calculator for a bathroom with a power shower and this the figure it came out with for a room of this size. I am currently moving 90 cubic meteres an hour and it is not sufficient - mould, condensation, rust etc . The replacement air is coming from the hall outside the bathroom.

[John Grabowski]

I have used a fan size calculator for a bathroom with a power shower and this the figure it came out with for a room of this size. I am currently moving 90 cubic meteres an hour and it is not sufficient - mould, condensation, rust etc . The replacement air is coming from the hall outside the bathroom.

*If you are ducting the fan outside then you need to have your replacement air come from outside as well. Otherwise you just create a vacuum and the exhaust fan does almost nothing. If your fan is ducted to exhaust in the house then the hall replacement air should suffice. Try opening a window in another part of the house whenever the exhaust fan is on and see if that makes a difference. 90 cubic meters is a lot of air. Off hand I would say that you don't have sufficient replacement air to actually have any significant flow.

As far as duct size you should go with the fan manufacturers recommendations.

[sligoNoSPAMjoe]

You do know the problems of all flexible ducts? At best the ridges greatly reduce actural air flow at worse they collect condensation causing other problems.

[Doug Miller]

What do you mean, "so much air"?? 247 cubic meters per hour is 145 cubic feet per minute, which isn't really all that much. Rule of thumb for venting a bathroom is 1.07 cfm per square foot of floor space, so that corresponds to an area of about 136 sq ft. What's the big deal?

[Michael Dobony]

I have NEVER seen a fart fan NOT ducted outside and they never had outside airflow supply. To do so eliminates heated or air conditioned air in that room. Instead, the return air should have a filtered fresh air supply.

[ransley]

Is heat forced air, try having fan run 24-7 for now. Spray mold with laundry bleach. If forced air maybe you need better supply and returns. There are alot of other possibilities like overhumidifying your home with a humidifier that you have not gone into. In winter ducting outside is a waste unless its new tight construction and you are to humid. There is alot more to the overall picture nobody knows about, is this a Steam Room.

[fullyabsorbent]

No this is not a steam room it is a normal bathroom. Only partly tiled aound the bath. A power shower is over the bath ie not an enclosed unit. The fan is threre to simply extract steam and condensation when the shower is on, in order to prevent the build up of condesation. The room is heated with a radiator. the room is not airtight and air is simply replenished from gaps around the door leading into an interior hall.

[ransley]

So how is house humidity, ductwork, you are missing the picture and dont get it.

[Phisherman]

Metal or PVC ductwork will move more air than flexible hose due to air turbulance. I use 4" metal ductwork for bath and clothes dryer exhaust.

[Handplanes]

Pick out the fan and see what the manufacturer recommends. Most likely the 4" duct will be adequate.

R

[Bubba]

Only one person missing the picture here ransley. It is ridiculously apparent that it is YOU! Would you like that stick now so you can beat your head in with it? Bubba

[nicksanspam]

But 90 m^3/h is only 53 cfm.

A better solution, IMO:

Nick