Cooker hood venting

[littlespark]

Ive been asked to replace a cooker hood thats gone "pop" and just by speaking to the customer on the phone, i think i know why.

Apparently, the ducting goes straight up, and through the roof... Not sure if its a bungelow, or goes another storey before going out the roof.

To me, i expect the hot air is cooling, condensing onto the duct as grease, and running straight back down into the hood. Unless a vertical run is permitted, and its just old age thats caused the failure.
Ill check how greasy the duct is when i go to see the job.

All i can find online installation manuals state 3m max ducting length, but doesnt specify horizontal or vertical.... and max 3 bends. (Howdens, Lomona model hoods)


I know the hood cannot be ducted straight out the wall, as there is a garage there... but maybe could go into the garage, then right angle bend, straight horizontal run to nearest outside wall.

Or block off vents and just use it as recirculating.

 

[Jock from the north]

Ive been asked to replace a cooker hood thats gone "pop" and just by speaking to the customer on the phone, i think i know why.

Apparently, the ducting goes straight up, and through the roof... Not sure if its a bungelow, or goes another storey before going out the roof.

To me, i expect the hot air is cooling, condensing onto the duct as grease, and running straight back down into the hood. Unless a vertical run is permitted, and its just old age thats caused the failure.
Ill check how greasy the duct is when i go to see the job.

All i can find online installation manuals state 3m max ducting length, but doesnt specify horizontal or vertical.... and max 3 bends. (Howdens, Lomona model hoods)


I know the hood cannot be ducted straight out the wall, as there is a garage there... but maybe could go into the garage, then right angle bend, straight horizontal run to nearest outside wall.

Or block off vents and just use it as recirculating.

Ventilation that is pulling air from a room that is 22 c or even more above a cooker then entering a loft that maybe minus 3 in winter or 16 if you live beside me will always produce condensation that will run down pipe ,flexiduct.using the correct type of ducting or even wrapping ducting in glass wool in loft can help this.i had a fan not to long ago with exact same issue ,tripping rcd because water was flowing back to fan connections .I had installed a 3 pole isolator which i do with every fan so customer was able to switch it off and rcbo reset.just as a side note I have found 1 or 2 litres in some horizontal ducting in loft ,wheather this is condensation or outside influences I couldn't say