looking for advice for fitting a hob extractor

[mims&pip]

We had the same set up at a previous house, but with two vents - one of which you can just get a glimpse of in the attached piccies*. Like Feltwell's, our opening was fairly tall - and we had at least 30"/760mm clearance above the gas hob, as our tiles were 6" x 6" - as I think is illustrated here. No issues at all as far as I can recall over the ten years we were at that property, Must confess though, we never involved Building Control when we did the work :roll:

*These are the best I have as we sold that house almost ten years ago

 

[Feltwell]

ooh- could I inquire as to the height of your chimney opening please? We need to get our chimney opening raised to facilitate the extractor above the hood, but I'm struggling to find a reference as to how high is 'normal'. I see an extractor should be 760mm above a gas hob, which gives us an opening height of of around 1800mm, but I'm wondering if this would look a little 'low'...

From the floor, the height at the edges is 1680mm and the centre height is 1730mm. The opening is 1150mm wide (it's an 1100 cooker in it).

1800mm should be fine, you wouldn't want it any higher I'd say even if you're tall . I'm 6'2" and even though the arch edge is a bit below my eye level I don't have to duck down to see the back gas rings on ours, I can see no problem looking down to them. Mrs F doesn't have to worry about such things!

 

[Penners]

We inherited a "vented up the chimney" setup - and I have to say it works fine.

It looks extremely nice, Feltwell (except I'm afraid your clock's wrong).

 

[Penners]

ooh- could I inquire as to the height of your chimney opening please? We need to get our chimney opening raised to facilitate the extractor above the hood, but I'm struggling to find a reference as to how high is 'normal'. I see an extractor should be 760mm above a gas hob, which gives us an opening height of of around 1800mm, but I'm wondering if this would look a little 'low'...

I don't know whether this is particular to our new range cooker, Parkview094, or whether it's a general rule, but the fitting instructions for the cooker state that nothing must sit lower than 650mm above the cooking surface (an electric hob). From what you say, it looks as though the figure is greater for a gas hob. However, I'm sure there would be no harm in increasing the headroom, although this might slightly reduce the extraction effect of a hood.

 

[a twig]

Being fairly tall, the last extractor I put in was well over a metre above the hobs, extraction worked well enough and was a relief to not smack my forehead or have to stoop.

 

[Bogart]

Still toying with options as to how to vent hob.It would involve a horizontal run of about 1.5m then a right angle up the chimney stack for about 4m approx. I have contemplated before doing anything having a bit of a trial run using smoke pellets. If I send smoke signals out from the roof will be happy the extract fan can handle it if not may install a separate more poweful fan.

 

[Abi Cott]

With the height of objects above a hob, the regs (AFAIK) state that the minimum height above a gas hob is 750mm, and 700mm above an electric hob.

These regs can be modified by the instructions of the hob supplier. So if you don't know for sure you design the gas hob to be 750mm below any hood, but if you have the manufacturers specifics for the hob and it states a hood can be placed lower, you are in the clear.

Its a bit like 'de-rating' when you are designing an electrical installation.

 

[a twig]

You may want to take a look at some of the more commercially oriented Kitchen Extractor Fan options here - http://www.justfans.co.uk/kitchen-fans-canopy-extractors-motor-only-c-26_52_82.html - in particular those which specifically say "good for venting up chimneys". Just bear in mind you will need to keep access to them to clean out the grease trays periodically

 

[JBean]

On whether recirculation filters have improved - our cooker is against a party wall and so external venting would have been very difficult. So we considered a hood with a recirculation filter, but our builder and electrician both advised against - they said it would be a lot of noise for little effect!

So we just open a window when necessary and (so far at least) have found that we have no problems. The tall ceilings and good 'ventilation' in an old house seem to allow smells and steam to dissipate much more quickly and easily than in our last modern 'box'.

 

[88v8]

Still toying with options as to how to vent hob.It would involve a horizontal run of about 1.5m then a right angle up the chimney stack for about 4m approx. I have contemplated before doing anything having a bit of a trial run using smoke pellets. If I send smoke signals out from the roof will be happy the extract fan can handle it if not may install a separate more poweful fan.

5ft sideways will only work if there is good airflow across the hob. If for instance the primary air inlet is between the fan and the hob, it will create a short-circuit that excludes the hob.
Try it with the internal kitchen door(s) open and closed.

As regards grease, what would be fine in a private home with a healthy diet, might eventually become a complete menace in some commercial kitchens.

In our previous house the fan (Aidelle Wallfan 6) was in the wall about 4ft above the hob and then went six feet sideways in smooth plastic trunking and out through a self-closing shutter. Worked well because there was an air-hob-fan circuit, and never needed cleaning because we don't do greasy. Somewhat to my regret

Ivor