In message , Martin Evans
writes
Hi We have oil fired boiler Camray quartet with one pump and two acl
lifestyle 2 port valves, everything has been working fine last few years but
now boiler and pump running constantly even with programmer set to off for
both HW and CH only way I can stop running is to turn of main supply to
system. Any ideas what problem could be.

Have the contacts in the programmer welded themselves together ?

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geoff