Drayton SM2 replace with LP241 - wiring issue

[Brendan1978]

Hi all, got a noob question, we cannot get a engineer out for weeks to do this job, so having replaced programmers before i thought i would replace our noisy SM2 with a LP241, knowing that the plates are identical... thought this would be simple... however!

The SM2 is currently wire up as follows
N - neutral
L - Live
1 - Blank
2 - Blank
3 - wire
4 - wire

The SM2 has a both CH and HW timers on it, but how can it work when not wired correctly? When i Installed the LP241 onto the plate the boiler was permanently on... sooo was wondering if anyone can shed light on this for me. Thanks

 

[D_Hailsham]

Do you have a fully pumped system with two motorized valves?

If so, make sure the link on the back of the LP241 is in the P position.

Does the problem go away when you replace the old timer? If so, and you bought the LP241 from a shop, take it back and tell them it's faulty.

If you have a multimeter you can test the LP242 yourself using the backplate which came with it and a length of twin cable with a 13A plug on one end.

Connect the other end to the L and N terminals of the spare backplate.
Mount the LP241 on the backplate
Plug in and switch on
Measure voltage (meter on AC volts 250V range or higher) between terminals 3 and N and between 4 and N with the timer set to the different positions. You should only get 240V when the timer is supposed to be on.

 

[Brendan1978]

Aye two motorised valves on it, will try tomorrow, forgot about the switch on the back of the lp241 too...