cooker hood makes wall vibrate

waxworks59

hi - our Elica cooker hood makes the wooden support wall vibrate. It happens on the lowest speed level

When I remove the cap that leads the air to outside, it does not vibrate. When I hold my hand above the cooker hood and block the air circulation, it starts to vibrate again.

Initially I thought this is a problem of ventilation, air that could not escape to outside. However I have simulated this with a hair dryer, using a plastic bag and sealed both the hairdryer and the pipe. There was no air escaping, which made me lead to think there is no problem here.

Then I bought a new motor, which I just installed. That has not solved the problem either.

Is there anyone who recognizes this and know what to do about it ?


just to add on, the cooker hood must be about 10 years old, and I de-greased it

waxworks59

I have now installed a smaller fan wheel, and that helped a lot.

I also discovered the vibrations are going through the hooks and the iron plate which is mounted to the wall. If I hold the cooker hood against the wall, but not hooked on that iron plate, it does not vibrate at all. So that is the problem.

Any idea how I can attach the cooker hood to the wall, not using the iron hooks ?

endacl

Sounds like a sympathetic resonance. This is physics though, not DIY! The vibrations may be caused by the two being 'in tune' with each other. Remember, a sound or pitch is just a steady series of vibrations. Maybe try rubber washers to dampen the transfer?

waxworks59

Thanks Endacl, I ll try that.

Another effect I have is.. the vibrations make the glasses in the cupboard next to the hood dance !

endacl

Ignore my previous! You have a poltergeist! Get out now!

:eek:

Sounds like you've a pretty musical kitchen.

Irish Steve

Sounds to me like the fan is out of balance, and needs to be checked, if possible.

Can you remove the fan from the motor, and mount it on a piece of suitable steel or similar so that it can be mounted between 2 vertical plates, and rotated.

The aim is to see where the fan rotates to when free to turn, and if it keeps rotating to the same position each time it is moved, then some sort of weight needs to be attached opposite to the low point to balance it. The objective is to arrive at a situation where the fan stops randomly when rotated, and doesn't have a low spot that it gravitates to when rotated.

Once that's done, it can be remounted on the motor, and that should help reduce the vibrations significantly.