Puzzling behaviour of an extractor fan

Joined
24 Mar 2012
Messages
435
Reaction score
23
Location
Lancashire
Country
United Kingdom
Hi experts. I don't know whether anyone can throw any light on this, but, about four months ago, I installed a new extractor fan in the bathroom The make/model is stated to be: GXC6EC kitchen fan with pullcord. It works fine and I am very satisfied with it.
A month after that, I installed exactly the same model of fan in the kitchen (above the gas-stove). When it was first switched on, it was just as it ought to have been — it ran smoothly and was fairly quiet, like the other one. However, within a week or two, it started to make a knocking sound, which, though only faint, is quite noticeable. It's as if one or more of the blades of the fan is catching, very slightly, on something. Yet, I don't see how this is possible because it locates within the casing on the wall, quite rigidly — surely, there cannot be any movement of the motor and blades, within the case? If it is left running for (say) fifteen minutes, the sound gradually disappears and it sounds normal. This happens whether the weather is windy or not.

The strange thing is that this does not happen every time. There are relatively rare times when, right from being switched on, it runs smoothly.

As long as this fan works, I am stuck with it. However, it would be good to find out why the slight knocking noise happens. Has anyone any ideas about this?
With thanks for any helpful comments,
L.L.
 
Sponsored Links
Congealed grease from the food being cooker and/or heat damage.

Quote from Install instructions

"" If installed in a kitchen, fans must not be mounted immediately above a cooker hob or eye level grill. ""
Well, that's straight from the shoulder! However, I don't think it can be grease, because we do very little frying. Besides, the noise started too soon after installation, I would think, to be caused by an accumulation of grease. As regards heat damage, I suppose the heat from the grill (about two foot six inches below the fan) could well have had an effect. That would never have occurred to me! It probably would not take long for heat to slightly distort the blades of the fan. So thanks for your remarks, Bernard. I can't do anything about this situation now, so I shall just hope it does not go worse.
L.L.
 
It might be that the wall is not flat, and tightening the screws distorted the casing. Try loosening the fixing screws and see if the noise stops. If so, tighten them gradually, one at a time, until you find the one(s) causing distortion. You could either leave that one a bit loose, or slip a few washers over the screw behind the fan casing.
 
Sponsored Links
It might be that the wall is not flat, and tightening the screws distorted the casing. Try loosening the fixing screws and see if the noise stops. If so, tighten them gradually, one at a time, until you find the one(s) causing distortion. You could either leave that one a bit loose, or slip a few washers over the screw behind the fan casing.

Yes, that seems to be a possibility, JohnD. I shall try that, when I get the time. I'm wrestling with a venetian bind at the moment.
L.L.
 
Congealed grease from the food being cooker and/or heat damage.

Quote from Install instructions

"" If installed in a kitchen, fans must not be mounted immediately above a cooker hob or eye level grill. ""
Bernard, I was wondering how it is with those cookers that have a hood over them. Don't they have a motor, of necessity over the cooker, to draw the fumes up? Just wondering.
L.L.
 
The motor and fan in the hood are specifically designed to cope with contaminated air from the hob, Also most hoods have a filter before the fan to reduce the amount of contamination that can reach the fan.
Ah, that explains it. Thanks.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top