Ever since the chimney was worked on my mother swears that the stove hasn't been as good, she says it burns okay for an hour or two then goes out. It has a metal disk with a small hole in that pivots at the top of the stove to control airflow into a large flue. That flue goes up then bends 45 degrees to the side then 45 degrees upright again. The flue then disappears into brick where it undergoes two 90 degree turns (accessible from the outside through a metal hatch) then goes straight up the chimney.
Any suggestions as to a sealer for the joins in the flue? I see Toolstation do a high temperature sealant on pg 202 (no. 66124) but the description says it's only rated to 300 degrees C. Would that be good enough?
Any suggestions as to why it's okay for a couple of hours only? It doesn't seem to depend on external wind speed or direction. Could it be the effect of a brick somewhere?