My central heating programmer has just stopped working – the display is blank and it doesn’t turn the heating on.

It’s a Drayton LP722.

There’s a separate thermostat, so all this thing does is control the heating times.

Until I can get a new programmer, can I just wire things up so that the programmer is bypassed and the hot water and heating are always on?

I’ve traced the wires back to a junction box. There are four cables going in – one from this programmer; one from a separate programmer for the kitchen UFH; one which I assume goes to the boiler; and one which goes to a pump (I assume for the UFH). This programmer has brown (which tests as live), black, grey and blue wires, all connected to same colour wires in the cable going to (I assume) the boiler.

I’m guessing I should wire up the black and grey from the boiler to brown from the boiler – but would like a little confirmation from STW before I do this.

Pictures of the programmer and wiring in case they’re helpful:

[url=https://flic.kr/p/qe8ykY]2014-12-23 14.33.11[/url] by sl2000, on Flickr

[url=https://flic.kr/p/qegcEv]2014-12-23 14.15.24[/url] by sl2000, on Flickr

Google an installation guide for your boiler. My Vaillant had 2 types of controller available. 1 was 24volt the other mains and they needed to be wired differently and jumpers applied in the boiler wiring..

But saying that, there’s nothing wrong in having the heat on permanently and controlling it via the thermostat. In fact I always leave it on permanent and control the temperature with a Salus Digital Room Thermostat which allows you to set different temperatures for different times of weekday and weekend.

If I were you, the first thing I’d do is stop guessing and assuming things. They’re not good bedfellows with mains voltage.

My central heating programmer has just stopped working

That’s a good excuse go and buy a Tado.

There should be an installation guide for your timer – it’ll tell you what wire does what by the position they were connected into the back of the unit.

search for ‘y’ plan to understand the wiring. This assumes you have wires form the junction to:

pump
mid pos valve
tank (hw thermostat)
Themstat (heat)

last two call for heat -activate the mpv – which activates the boiler call/relay -> back down the boiler. The clock provides the (timeswitched) live feed to these. ALL THIS IS 240V!! Isolate first and check twice!!

The key to it all is the ‘mid position valve’.

The clock will switch live – almost certainly.

You may more unlikely have s plan (two valves)

Google an installation guide for your boiler.

OK – done that – it’s a worcester greenstar 30cdi and according to the manual on page 26 it takes mains voltage switching.

But I’m assuming (sorry Cougar) that all the programmer did when it worked was switch the inputs rather than transforming voltages.

That’s a good excuse go and buy a Tado.

That’s what I’m thinking – so it may take a while to get the new programmer rather than simply nipping down the local plumbers merchant.

ALL THIS IS 240V!! Isolate first and check twice!!

Yep – will do.

The clock will switch live – almost certainly.

OK – I’m taking that as go! Wish me luck.

It will be something like this – if you have HOneywell – google image search – the colours (orange from vlave etc.) will be consistent. Wire terminal 1 to the relevant hw and heat for permanent on.

This assumes your timer is kaput. IF it is still telling the time, your vlave is probably stuck and not completing the circuit to call for heat – if it’s a HOneywell 4073 you can just move the switch on top.

PS I am not a plumber! the circuit above is pretty plain. CONFIRM IT REPRESENTS YOUR SYSTEM FIRST- TAKE 5MINS TO IDENTIFY THE COMPONENTS AND WIRES – MAKE NO ASSUMPTIONS 8)

I have heat! (And I’m still alive.)

Thanks for everyone’s help.

Hurrah! No fried fingers! Your house will now reach 37deg! 🙂