Worcester 24cdi boiler replacement digital timer

[lampieuk]

Hi there ! 1st post, so please be gentle !

Just moved into a new house and as a welcome "gift" the previous owner informed me that the old mechanical timer on the boiler was on it's way out. I have purchased a new digital timer for the boiler and connected it to the ST5 connector as per the instructions.

However now, the boiler does not fire up when switched to on. I read in a previous post that in order to get it working, you need to link together the LS & LR connections on the ST8 connector, but mentions that this is only if you do not have a room thermostat connected and we do.

Does anyone have any ideas how to get this digital timer working & still have the room thermostat working ?

Many thanks

 

[Andygasman2010]

It should just be a straight swap, no problems.

Is the clock powered? If so, does the red light come on when you select "on"?

If you disconnect the clock completely does the heating come on?

 

[lampieuk]

Hi,

Cheers for the reply.

yes, the digital timer is powered and the red light is on, but the boiler does not fire up. When I put the analogue timer back in everything is ok. On the ST8 connector there is a black wire connected to LR and a brown connected to the right most terminal (not labeled) these come from the room stat. Also there is a blue wire going to NS, a brown going to LS and a grey going to the right most terminal and brown wire (these come from the manual timer which I disconnected when I installed the digital timer. Which wires to which terminals should be left in the ST8 connector once the manual timer has been removed ?

 

[Andygasman2010]

Look a little further to the right on the PCB connections, you should see a connection called ST13. Is there a link between terminals 1 - 2 (the first two from the left) ?

 

[lampieuk]

As mentioned above, the mechanical timer was wired to the ST8 connector. The blue wire going to NS, brown going to LS and grey going to the right most terminal (not labeled). I disconnected these wires when I removed the digital timer. One thought, should the wires from the room thermostat stay as they were after the manual timer removed ? I.e black wire to LR & brown to right terminal (not labeled) ? Just thought, I think I left these disconnected when trying last time ?

 

[Andygasman2010]

whichever wires went to the switch on the mech timer need to be linked together

 

[Andygasman2010]

the roomstat should stay wired to LS and LR

 

[lampieuk]

Does it matter which colour wire from the room thermostat goes to LS and which to LR ? I have a black wire and a brown ?

 

[Andygasman2010]

no, so long as the blue goes to NS as it's the neutral.

 

[lampieuk]

Success ! Your comment about the blue wire going to NS made me think there was no blue wire coming from room stat, but pulling back the outer casing, there it was, cut back. Wired blue to NS, black and brown to the live terminals and switched on ! All now working fine ! Many thanks for your help !