Hi,

I have recently had my programmer replaced to a Randal 715 with
seperate controls for CH and HW. The programmer was set for a fully
pumped system determined by the existence of a motorised valve and
only two pipes connected to the boiler. However my problem occurs
when the programmer is set to off for both HW and CH but the boiler
still fires when the room thermostat is turned up!!!!

I have checked the wiring on the programmer and no connection is made
to the 'HTG Off' as was the previous programmer (Randall 702), could
this be the problem? I can get HW seperately recently and when just
wanting CH this also works.

I have three wires going to the room thermostat but the yellow (wired
to terminal No. 3) appears not be connected to the programmer's wiring
plate.

I switch the programmer to 'gravity' based system and now the CH comes
on only with the HW and is not effected by the room thermostat when
the system is off.

Is there anything I can check to confirm what type of system I have?

and how is the room thermostat controlling the boiler directly?

Many thanks

Adam.