Linking hood extractor to inline fan

[daven1986]

Hi all,

I have to have a fairly long duct run for my kitchen extractor hood and the bathroom extractor will also join onto this run. To avoid smells getting into the bathroom, and to ensure the kitchen extractor works well, I was considering putting an inline fan after the join and wiring it to both the bathroom lights and the kitchen hood so it would always come on when either were used.

Is this possible / sensible?

Thanks

 

[Tigercubrider]

Couldn't you just have an inline draught flap?

 

[winston1]

You would need double pole switches in the bathroom and cooker hood otherwise the bathroom light will come on whenever you use the cooker hood.

 

[ban-all-sheds]

Is this possible / sensible?

You'd better ensure that the filters in the cooker hood trap every single molecule of grease, or the long duct will become a health hazard and the second fan will become clogged.

 

[John D v2.0]

I'm pretty sure multi point extraction is a controlled fitting under building regs and has to be commissioned properly to ensure the extraction rates are correct. The terminals would need balancing to get the 15l/s in the bathroom and 30 in the kitchen, at the correct power consumption and noise level.
Is there any reason you can't duct separately other than convenience?

 

[daven1986]

Thanks for the replies, i can't duct separately due to space, the runs would have to overlap.

I don't think this is multi point extraction, the kitchen will have a good with a fan, it will just into a duct with an inline fan that serves the bathroom. It isn't one fan sucking from many rooms.

When i say long, i mean around 5m for the kitchen run and 3 for the bathroom, so 2m of overlap.

 

[John D v2.0]

Thanks for the replies, i can't duct separately due to space, the runs would have to overlap.

I don't think this is multi point extraction, the kitchen will have a good with a fan, it will just into a duct with an inline fan that serves the bathroom. It isn't one fan sucking from many rooms.

When i say long, i mean around 5m for the kitchen run and 3 for the bathroom, so 2m of overlap.

You're going to struggle a bit then.

Multi point extraction is doable by balancing the terminals and sizing the ducts properly, then it should hold an equilibrium. But having two fans running in series is going to be an interesting challenge! The second fan will need to be big enough to extract all the air from both primary fans. And by that time, you may as well not bother with the primary fans. Give it a go and see what happens I suppose! As said above, you'll need an extra "pole" on each switch, so that the second fan can be controlled via the same switches but without causing the other light to come on.

 

[daven1986]

Many thanks John D, I will give it a shot!