Extract vent near boiler flue

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I have a gas boiler in my kitchen with the flue running about a ft then out the wall. I have fitted a new kitchen and wish to install an extract hood, but the only place to extract from the hood to outside is above the flue outlet outside. If an automatic closing extract grid is used so that the grill closes when the extract is not in use is it ok to install the hood extract above the boiler flue externally?

Thanks

Dave :D
 
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No, autoclosing will make no difference. How close to the flue it will be is the decider, which will be stated in the manufacturer's instructions for your boiler.
 
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Unfortunately we have just bought the house and there are no instructions for the boiler! The 4" extract grid would be about 3" above the boiler flue. The boiler flue itself extends 2" from the wall before the flue expels the fumes. I thought as the extract grill closes when not in use no fumes would get in and when the extract fan is running it will be blowing so no fumes should come in.
 
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Unfortunately we have just bought the house and there are no instructions for the boiler! The 4" extract grid would be about 3" above the boiler flue. The boiler flue itself extends 2" from the wall before the flue expels the fumes. I thought as the extract grill closes when not in use no fumes would get in and when the extract fan is running it will be blowing so no fumes should come in.

Sounds good, until you realise that with the fan off, if the grill sticks open like they do, fumes can come back in. Anyway, 3" isn't enough I'm afraid, so you can't do that.
 
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You need 300mm (12") from ANY opening in your wall to the boiler flue, assuming it is a fan flue, balanced flue will need 600mm.
 
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