During the summer we tend to turn the TRVs to the off position - the valve head bears on a pin and presses it down in the closed state. Quite often when the winter arrives and we want heating we turn the TRVs up to get the hot water flowing but the little pin stays stuck down.
Take off the TRV head(s) and pull up gently with a pair of pliers.
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Good Luck...
November 2015
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