Extractor Roof vent tile identification

[goodnightspoons]

I recently had an Elica Slim 60 cooker hood installed, with external venting.
On setting 1 it is very quiet, almost no suction. On setting 2 and setting 3 it sounds the same - very loud. It seems to be all or nothing.

The ducting is 6 inches, as specified in the Elica installation guide. It's vented through the roof, via the vent tile in the pic below. There are no kinks / corners in the ducting - it's pretty much straight up and out. Does anyone know what kind of vent tile this is / if it is appropriate? I've asked the builders but haven't had a reply yet.

We've had the Elica engineer round and he disconnected the ducting and it seemed to solve the problem (Setting 1 sounds low, setting 2 sounds medium and setting 3 sounds loud, as they should). So they suspect some kind of obstruction in the ducting or vent tile.

I'm waiting for our builders to come and inspect the ducting/tile (I don't have a tall enough ladder!) but in the meantime, has anyone experienced this issue? I doubt there is any obstruction as it's just been installed. Unless the vent tile is not appropriate (eg the air flow rate of the tile is less than the suction of the cooker hood)?

 

[Murdochcat]

How long is the air vent pipe

 

[goodnightspoons]

How long is the air vent pipe

the ducting is probably around 4-5 metres between the top of the cooker hood, and the vent tile in the roof

 

[goodnightspoons]

I purchased a big ladder and finally got into the loft... this is what it looks like. Acceptable? or No?

 

[foxhole]

The ducting is reduced to 100mm at vent so will increase resistance and noise.

 

[goodnightspoons]

Yes, it looks like it's reduced. I had told the builders it needed to be 6 inches throughout, with no reduction in size. But looks like they used a vent with the wrong connection size?

Also, could the length and curve in the ducting be worsening the noise?

I don't understand why they didn't install the vent directly above the hood...

 

[foxhole]

Is there an external wall above oven?
The plastic hose used is unsuitable for kitchen use as the heat passing thru it will melt holes in it .

 

[JohnD]

Old hoods, and cheaper extractors, used to be 4"

Better kitchen hoods are now 5" or 6"

IIRC a 4" vent only has half the capacity

So it does look like the restriction is the problem in your case

In your case you need a larger roof tile

An experienced roofer would know more.

 

[datarebal]

The vent slate is suitable for 100 to 110 mm .pretty standard .
This one is by klober , I think rarely seen these days
You will struggle to find a vent slate to take 150mm duct .
It'll need to exit through the roof with a lead slate and a mushroom cowl.
If the duct is left disconnected it's pumping moist air into your loft

 

[JohnD]

Foxhole mentioned venting through an external wall.

Does the kitchen have one?

 

[^woody^]

You should be specifying a roof terminal, not a vent tile. Terminals will take wider duct.

Also, every bend in the duct reduces extract performance, and noise potential. As does unsecured duct.

 

[noseall]

It'll need to exit through the roof with a lead slate and a mushroom cowl.

Thats how we do ours...

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