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Chimneys & Fireplaces Question
Upstairs chimney breast getting warm/ hot
Just had a 4.7kw Carron multifuel instlled. Very pleased. Twin wall s/steel flexible liner which was supposed to be vermiculite backfilled.
Downstairs chimney breast is just warm. However it is warmer near the downstairs ceiling, then warmer throughout upstairs chimney breast. Its not hot hot, but its more than warm.
House is a 20s semi. The stove replaced an open fire which needed chimney repointing I think.
Is this an issue? Is it safe? COuld it just be not enough vermiculite was used?
Even though your chimney has been lined and backfilled with vermiculite, the size of your 1920's chimney flue is only 225mm X 225mm and the diameter of your new liner is 150mm. With this type of liner installation it would be impossible (unless you break into the chimney) to guarantee that the liner does not touch the internal brick chimney wall (therefore transferring heat through it). Your original open fire would have flue gas temperatures of 500 - 600 degrees, whereas your stove flue temperatures should rarely go above 300 - 400 degrees. The idea of a stove is to heat your house in the way it was designed by heating the bones of the house. The clay bricks that your chimney is probably made of should be looked at as thermal mass that stores energy and releases it slowly. The only issues that arise from this are
1. If your chimney was not thoroughly swept before installation there may be soot or tar deposits that could ignite where the liner touches.
2. This is a perfect example of why a stainless steel flexible liner should not be used in a thatched property as the touching liner can transfer enough heat to ignite the thatch.
In all cases make sure you get the chimney swept at least once a year.
Answered 19th Aug 2013