Can a flue take two 90 degree turns?

6 Nov 2013
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United Kingdom
Just worked out the position I want to put the boiler with a vertical flue is going to be a problem.. The flue would hit the hip of the old roof structure (before the extension was done).. I can't use a horizontal flue because there is a carport going on the driveway so the flue has to be vertical..

Want to work out what to tell the gas man to do or if I need to move the kitchen around a bit (the expensive option)..

So the question is can the flue go 90 degrees at the top of the boiler then horizontal across the cupboards for say 500mm and then 90 degrees vertical and up out the roof?

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You need to refer to boiler manufacturer's limits on flue design. Details will be included in their installation instructions.
Most modern boilers can, there is a limit on how many metres of flue you can have, usually an elbow is counted as half a metre of flue so two will reduce the maximum run by a metre.
Elbows are normally worth a metre of flue 45 degree bends are half a metre. Get your gas engineer over and he will be able to figure out if it can be done.
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With a vertical flue its usually easier and gives a reduced effective length to go straight up and then offset it horizontally using two 45 degree bends.


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