you can't judge nothing without knowing what system it is maybe just a sticking zone valve.
hi-spec plumbing & heating (essex), September 2008
Wiring fault - if you have a electronic clock could be its internal switch has fused together first check you have a 3 amp fuse at the main switch. Could be an electrical fault that has fused the internal switch in clock. Electrical safety checks need to be done.
o, September 2008
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I can answer this question...
The boiler and burner switch on even though the time clock is switched off?