First(ly), I don't think there is any fundamental problem with a dual hood approach. But I think that potential configurations have to be evaluated by picturing the rising effluent plume and what it does when it gets to the hood.

Questions to ponder while keeping in mind that the lamp areas and other non-baffle/non-mesh areas do not count as hood aperture include:

o Does any part of the rising and expanding effluent not strike a baffle or mesh area?
o If so, where does it reflect to (curl away to) and is this location a baffle or mesh area that can capture it?
o If effluent escapes, is it a small enough fraction that it is tolerable?
o Is the type of effluent that escapes dependant on configuration? I.e., does the burner configuration (with the volcano in the center), in concert with what is cooked on which burner, affect the answers above?

Second(ly), I find it hard to believe that a pair of size X hoods with blowers costs significantly less than a size 2X single hood with a 2X-capable blower. Perhaps a bespoke hood shop similar to Modern-Aire in the USA can put meet your price point, or further searching of alternative may be fruitful.

kas

Thanks for reply. Yes most of the hoods sold in UK are 200cfm to be used with hobs and 500 cfm to be used for ranges. Also the ones to be fitted inside cabinets are all 11inch to 15inch wide. The chimney types are upto 22 inch wide but they will have those lights and buttons under hood so actually mesh area is smaller. Really struggling to find something that is deep enough and has enough power.

First I thought of mounting one 500 cfm hood and a seperate extractor fan like the ones used in bathroom but then i thought it is more important to capture all smoke/smell near the hob itself rather than letting it flow away and trying to capture by a bathroom like extractor.

I would prefer to mount two side by side instead of one behind other as that will be closer to the manufacturer's instruction, though no where it says you cant mount them one behind the other.

do you think if i mount two hoods side by side, though not deep enough to capture the front burner but enough to capture the back burners, they would be able to extract it out effectively from back burner. Will the extra width reduce the power they will have to capture it?

I have huge windows in the kitchen and I will open the window on other side of extractor to provide MUA. The weather isnt extreme here and it always feels ok to have some fresh air while cooking.

Effluent escape is constrained by walls and side cabinets so that the major escape path is on the side.where the cook stands in such configurations. This is ameliorated by having enough overlap of hood with front burners. But if you don't have enough, you can still choose to use back burners for the most greasy or smelly cooking.

I don't think it matters from a manufacturer's point of view whether the units are side by side or front by back. I would aim to keep the filters proximate for good collection at least in their portion of the apparent aperture area. (The area where impinging effluent is certain to intersect mesh filters and baffle areas, or be directed to them, is the only real aperture area.)

kas

Thank you very much for reply. In summary as long as I make sure that Effluent from back burners and to some extent from the cental burner are captured by the mesh part of the hood and two hood together have enough cfm, it would be ok.

So much to plan and choose for the refurbishment, I had never thought finding a hood would take so much time. Your explanation has put my mind to rest about this now and I can focus on other things.

If the cook top is against a wall I would aim to maximize capture of the center burner as it looks from your link like the one most capable of high pan heating. Higher temperatures cause higher effluent velocities and drive the flow rate needed at the hood. A high velocity effluent is harder to capture and contain if it isn't directly captured and contained (no bounces). The back burners' effluent plumes will be directed by the walls and side cabinets toward the hood aperture and have a reasonable chance of capture and containment.

Of course, if the center burner is intended just for boiling pasta, and the back burners will be frying the mackerel, then emphasizing back burner capture and containment will make sense.

For a good mental image of what goes on, see Schlieren image on page 4 of

http://www.energy.ca.gov/reports/2003-06-13_500-03-034F.PDF

kas

Kas,

Thanks a lot for help. I went through the doucment and now going for this hood
http://www.johnlewis.com/store/elica-elbht80-built-in-cooker-hood-grey/p230412069?navAction=jump&_requestid=9185062

Two hoods will be mounted inside a wall cabinet which will be 60 cm deep such that lights from the backside hood will be near wall and front side hood will be near the cook. Hopefully that will capture the cental burner. Also the hoods will be 31 inches above the hob, that can help with capture.

kitchen update is due in Jan next year. Will post an update how it goes.

Daisy08:

Seems like a suitable compromise. I see that the lights are mounted on a sloped panel which should help direct plume edges toward the central meshes. You may wish to sketch a stick figure side view to scale and consider whether the rear lights beam pattern (if you can determine what it is) will induce too much visual glare.

Please note that mesh filter hoods are only effective when the air flow through the mesh filters can be maintained, and that requires cleaning them whenever there is noticeable grease and lint build-up. Dishwashers may work for this, but some discoloration of the typical aluminum used in meshes may occur. A stainless steel mesh would be pretty immune to any caustic dishwasher detergent.

kas

Also, access to the controls of the rear unit may be an issue.

you observation about light is right. I think it will have seperate on/off for lights or I can remove bulbs from the back side hood and only use the front lights. Yes will have to wash those filters regularly. I will do anything to get rid of all the cooking smell and grease!

Anything?

Here is a link that might be useful: