Stoves cooker hood

[DavidMere]

Hi, can anyone help with this?
My new Stoves Sterling cooker hood 444410831 has 150mm cylindrical trunking which reduces after a 90 degree bend into box trunking 200mm x 60mm, then out through a tile vent.
The reduction in flow is about 33%, which doesn't sound a massive amount.
When the extractor is set to minimum there is a sensor that detects the reduced flow and sets the fan to maximum output. This is very noisy and annoying!!
I have read that it is possible to reduce the power sent to the fan using a potentiometer or resistor.
Has anyone done this and if so how would I find a technician to do this work?
Thanks

 

[JohnD]

Where is this restrictive trunking?

 

[DavidMere]

Thanks for you rquestion.
Where the trunking goes through the ceiling this 90 degree bend is located (the other way up) converting from 150mm circular to 200mm x 60mm rectangular.

 

[aveatry]

The flexible tube will not help the flow. I recently did some research on my extractor hood and you start with so many meters of straight length as a max and for every 90 degree turn you take off a few meters so it just shows you what even 1 turn can do to the flow.

 

[aveatry]

Thanks for you rquestion.
Where the trunking goes through the ceiling this 90 degree bend is located (the other way up) converting from 150mm circular to 200mm x 60mm rectangular.

View attachment 333798

Yes that is where your problem is. Is there space to go bigger that 60mm tall.

 

[DavidMere]

Many thanks.
I know where the problem is, my question was about finding a technician to install a potentiometer or resistor to override the sensor giving full power to the fan motor.

 

[aveatry]

Sorry

 

[JohnD]

do you mean you cannot increase the trunking to the correct size?

if your only option is to tinker with the control circuitry, I would have thought disabling the sensor would be simpler.

 

[DavidMere]

That sounds like a good solution.
Where is the sensor located?

 

[JohnD]

No idea.

Motor speed controls use electric wizardry. It might be measuring load on the motor caused by obstructed flow.

A circuit builder can buy ready made control circuits, but not something I know about.

Ask @bernardgreen

 

[jj4091]

"I have read that it is possible to reduce the power sent to the fan using a potentiometer or resistor."

Was that specific to your model or a generalised suggestion. Your idea may or may not be feasible but I doubt it will be economically viable