"raden" wrote in message
...
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 ?



If there are two valves it suggests an S plan system so the current drawn
through the programmer contacts is negligible (valve motor only) I'd suggest
the contacts in one of the motorised valve limit switches might be the
culprit. In each valve cable there will be an orange wire and a grey wire
from the limit switches. These will be connected together in the wiring
centre terminal box (orange to orange and grey to grey) with a live feed to
(usually) the grey wires and a switched supply from the orange wires to the
boiler and the pump. Carefully seperate one grey at a time from the terminal
(isolating while doing this or you will get the little men up your arm) and
try each time to see when the short circuited one is found. You then have a
choice of changing the microswitch which is a buggering about task or
changing the valve head if its of a vintage with a removable head and a five
wire swap, just keep a note of where the old wire colours went before
pulling them apart.