Help needed please

[Dougie212]

Hi there,

I was hoping someone out there may be able to help

I have a Valliant Combi in good Boiler, reasonably old, but works a treat until today.

Hot water is working fine...

The central heating however wont come on - now, its operated through a timer and a downstairs thermostat. I have checked the glass fuses on the boiler everything is fine and as I say, it fires up when we turn the hot taps on.

The timer however, although I can hear the timing mechanism the small light which shows when the boiler on is not working. Ive tried it on all settings (twice,once,24hr) and still nothing.

The timer is an EMT 2 with the British Gas logo on, and was fitted about 5 years ago..

My gut feeling is that something in the timer has gone. The thermostat seems ok, Ive checked the wiring and that was only replaced about 18 months ago.

Does anyone have any knowledge before |I open the timer up if it has its own fuse and if this is the likely cause or should I be looking for something else.

Kind Regards

Duncan

 

[Dan Robinson]

You'll need to be a little more specific than that about the boiler.

 

[Dougie212]

a GB240H I believe..thanks

 

[Dougie212]

Just to rule out everything, does anyone know of a way of firing up the boiler and bypassing the thermostat please?

 

[MANDATE]

Why would you want to by pass the room stat at this stage.
It would be wiser to check the room stat, which is only a 'switch'
Is electricity going into the stat? and does it work as a switch by turning it up/down so electricity comes out of the switch.
If it's not receiving electricity, then it's proof the the problem is further back at the timer. Sounds as the timer motor is ok if you can hear it. I would think it more likely a case of poor contacts.

 

[Dougie212]

hiya... thanks for your response.. I've metered for power at the stat and there is none neither in or out. I've just checked for ohms across the stat and its adjusting with the adjustment so, i'm thinking that this means its working...

When you say loose connection is this something I should be looking at in the timer box..??

 

[Space cat]

Since you seem competent enough with a meter, I suggest you identify the switching terminals on the timer - trace the wires if you have to - and do the same tests as you just did with the room thermostat. My guess is that it's not doing its job.

 

[MANDATE]

I doubt if it's a loose connection but you never know!
I also doubt if it's a broken wire between timer and stat.
Timers usually have pegs or cams to lift/lower contacts or operate micro switches which contain contacts.
I'd be looking for either:
cam/peg worn and not moving enough for contacts to 'make' circuit.
Or the actual contacts being burnt/dirty so even when 'made' they do not allow power to pass across.
As space cat says it can be checked out with a meter.

 

[Dougie212]

well... metering done... and upon removing the outer case, to my horror was the evidence of burning on the inside of the outer case.. something on the board has blown..with some umpf as well...

At least I can clearly see what the problem is.. Strangely, my wife mentioned she could smell burning plastic 2 days ago... that must have been it..

So my new question is, is there a direct replacement for the EDT2 timer still available..?? If so any recommendations? at present we have a manual timer but as I'm replacing it, a nice digital one would be good.

Many thanks

 

[MANDATE]

Is it EMT2 or EDT2 ?
I found this http://www.heatingcontrolsonline.co.uk/acl-drayton-invensys-lifestyle-lp711-timeswitch-p-186.html

 

[Dougie212]

My bad.... heads a shed... its EMT 2..

Thankyou

 

[Dougie212]

http://www.screwfix.com/p/drayton-lp711-timeswitch/39024?_requestid=146852

This is the same thing isnt it?

 

[MANDATE]

Yes it's the same model and should be easy to change or have you already changed it.