Hi Folks,
I had an idea, and I wondered if anyone could suggest some suitable components. It might sound completely mad, but hey, nothing ventured, nothing gained.
I have a big cooker hood that is vented to an external wall, via a stainless steel 6 inch cowled vent with a non-return flap. If you want to look at a picture of one, you could paste "Stainless Steel Wall Air Vent Cowled Hooded Extractor Non Return Flap" into a search engine.
The problem with these vents is that when the wind blows past them (rather than straight at them), the non-return flap bangs like crazy. If you fit a spring to the flap, it improves things, but if the spring is strong enough to really stop the noise, it makes the flap hard to push open, and consequently overstrains the extractor fan (and makes it noisier). And where I live (on a hill), it's windy a lot of the time. So I need a way to keep the flap properly open when the fan is running (as well as a wind generator, but that's another story).
So I thought it might be possible to use an electromagnet, positioned to hold the flap open against the spring, and link it to a relay controlled by the on/off switch of the extractor fan.
There are a couple of obvious issues (and I'm sure there are others I haven't though about). The first is that the extractor fan runs at 240V, and you wouldn't want a 240V component, so you would need some kind of basic step-down transformer. Secondly, the electromagnet would need to be small and (to some extent) weather resistant, not to mention quite powerful. It would be protected by the cowl, but we're looking at a damp environment (outdoor air). Plus, I have no idea how strong a small 12V (I'm guessing) electromagnet can be.
And no, ditching the flap is not an option. The house has to be heated, so you don't really need a 6 inch hole in the wall.
So it might end up an impractical solution for what is very much a first world problem; although trust me, those flaps can be pretty tiresome after a few hours.
All constructive ideas welcomed.
Cheers,
John M.
I had an idea, and I wondered if anyone could suggest some suitable components. It might sound completely mad, but hey, nothing ventured, nothing gained.
I have a big cooker hood that is vented to an external wall, via a stainless steel 6 inch cowled vent with a non-return flap. If you want to look at a picture of one, you could paste "Stainless Steel Wall Air Vent Cowled Hooded Extractor Non Return Flap" into a search engine.
The problem with these vents is that when the wind blows past them (rather than straight at them), the non-return flap bangs like crazy. If you fit a spring to the flap, it improves things, but if the spring is strong enough to really stop the noise, it makes the flap hard to push open, and consequently overstrains the extractor fan (and makes it noisier). And where I live (on a hill), it's windy a lot of the time. So I need a way to keep the flap properly open when the fan is running (as well as a wind generator, but that's another story).
So I thought it might be possible to use an electromagnet, positioned to hold the flap open against the spring, and link it to a relay controlled by the on/off switch of the extractor fan.
There are a couple of obvious issues (and I'm sure there are others I haven't though about). The first is that the extractor fan runs at 240V, and you wouldn't want a 240V component, so you would need some kind of basic step-down transformer. Secondly, the electromagnet would need to be small and (to some extent) weather resistant, not to mention quite powerful. It would be protected by the cowl, but we're looking at a damp environment (outdoor air). Plus, I have no idea how strong a small 12V (I'm guessing) electromagnet can be.
And no, ditching the flap is not an option. The house has to be heated, so you don't really need a 6 inch hole in the wall.
So it might end up an impractical solution for what is very much a first world problem; although trust me, those flaps can be pretty tiresome after a few hours.
All constructive ideas welcomed.
Cheers,
John M.
