installed a potterton ptt2 cylinder stat to replace a ptt1 that had burnt out. dam thing would`nt work. Rang tech and they said ptts not compatible will potterton 3000 time switch in use ??? guy on other end of phone told me to remove swiched live for cooling on cylinder stat! the sysyem is a `Y` plan so this idea sucks (hot water won`t turn-off) end up just installing a drayton cylinder stat, works fine. anyone had problems with potterton?