On Sat, 26 Aug 2006 02:35:29 +0100, diezeltruck wrote:

Hi,

The programmer that controls my central heating and hot water fails to
communicate with the boiler and the boiler is continually 'ON'

Do a google for 'S plan'. You should be able to come up with wiring
diagrams for all the common variations of heating system.

The programmer is set at 'OFF' but the boiler still fires

Wiring mistake, possibly

The RET Electronic Room Thermostat that controls the central heating
also fails to switch the boiler off even when turned fully down.

Wiring mistake, possibly

Because of this my central heating is continually 'on' and the
thermostat fails to switch do anything in controlling the room temp as
the boiler fails to switch off.

It has been suggested that I have a faulty motorised valve which is
stuck in the 'on' position.

That alone won't give rise to the symptoms you describe. If the system has
been wired properly, then the controller overides any other auxiliary
switches (like the thermostat, the aux switches on the valves) in the
circuit.

I assume that the motorised valve operating the central heating may be
faulty.

There seems to be 2 motorised valves beside my water tank:-

1 - Synchron HPA2 Actuator/HPV26 valve(plastic box/white cover)
2 - Synchron 272848 Honeywell Motorised valve(metal box)

But which valve of the two is faulty?

1 is situated just above and in line with the pump and feeds into the
top of the cylinder tank

2 is situated off of the main pump and and then travels down to the
ground floor.

I guess that 2 is the one that controls the central heating?

All the wires that serve both valves go into a junction box so it is
easy to isolate each valve but which one?

Will changing just the actuator resolve the problem because having had
both actuators off each valve appears to turn except that 2 valve is
what I could say a little stiff and jerky.

Will I have to drain the system?

There appears to be alot of 'stop taps' above and below each valve
which sould facilitate removing of the valve.

I am tempted to just change the actuator!!

What does anyone think?

Start with the junction box if you're happy to investigate the wiring.


--
the dot wanderer at tesco dot net