Central heating system switch does not work consistently

[lumepo]

View media item 58093
I had people staying in my house and do not know what they have done. The central heating system switch does not work consistently:
1 - When the switches for hot water and central heating are switched off, sometimes the light for hot water switch remains on and after a while switches itself off automatically.
2 - There are 2 small black knobs on the right hand side that are loose (I have marked them with red arrows). The one at the top is much so that the bottom one. I am not sure if they are damaged.


The make of the switch box is LANDIS & GYR. Are they easy to change if mine is damaged? If I have to change it where can I get it from?

Thank you in advance for your help

 

[Taylortwocities]

Cannot see your picture.
Please follow these instructions on how to upload it so we can see it. //www.diynot.com/forums/viewtopic.php?t=129539

 

[lumepo]

View media item 58094

My apologies. Here is the central heating switch box

 

[Taylortwocities]

Its mechanical and worn out.

Yhere are lots of options. My suggestion is one of these.

It should come with a "how to swop it for the one you have guide".

http://www.tlc-direct.co.uk/Products/HOH27.html

 

[stem]

1 - When the switches for hot water and central heating are switched off, sometimes the light for hot water switch remains on and after a while switches itself off automatically.

I've come across this a few times and it's quite normal. My guess is that the system is wired up as a 'Y Plan' with a 3 port motorised valve and a live is fed back to the programmer from the "hot water off" signal via the hot water cylinder thermostat. When the hot water cools and the thermostat switches over to 'call' the light is extinguished, hence the delay you mention.

Not all programmers do this, it depends how the light is wired inside the programmer by the manufacturer. You can test it very simply. Next time you notice the light is 'on' when the HW is off, turn the hot water cylinder thermostat down until it clicks and see if the light goes out.

However that model of Landis & Gyr must be about 30 years old, so probably a good time to replace it anyway.

 

[lumepo]

I am extremely grateful for all the replies to my question, particularly to the last. It is most informative and helpful. I will change the switch as soon as I can. I hope it will not be too difficult to do so.

 

[stem]

When you say "change the switch" I assume you mean the programmer / timeswitch, not the thermostat on the hot water cylinder.

 

[lumepo]

I will change the programmer / timeswitch

 

[bhm1712]

I recommend this:

http://www.screwfix.com/p/siemens-rwb29-multi-choice-programmer/65118?_requestid=291101

As it is much more user friendly than the Horstmann and looks a darn sight better too. It will fit right onto the existing backplate.

 

[Taylortwocities]

It will fit right onto the existing backplate.

Really

I dont think the old L&G stuff had a backplate.

But I stand ready to be corrected!

 

[bhm1712]

It will fit right onto the existing backplate.

Really

I dont think the old L&G stuff had a backplate.

But I stand ready to be corrected!

Well the one pictured is the same as the one i replaced with the siemens RWB29. The one pictured is the L&G RWB2. It has a backplate. I can assure you. This timer was marketed by many companies and branded such as Glow-worm Mastermind and Potterton Mini-Minder.

 

[bhm1712]

On the left hand side below the dial, there will be 2 small screws. Undo these with a screw driver and once fully undone (they dont come all the way out into your hands unless you force them and break the retainer clip) you need to pull outwards and upwards from the bottom, so as to pivot. The timer will then pop off the backplate. Fitting the new one is a reversal - just locate the 2 tabs on the top opposite the screw holes, and pivot down from the top and inwards until you feel the pins locate with almost a click. Beware, there will be live 240 here. Isolate the CH system first.

 

[bhm1712]

On the left hand side below the dial, there will be 2 small screws. Undo these with a screw driver and once fully undone (they dont come all the way out into your hands unless you force them and break the retainer clip) you need to pull outwards and upwards from the bottom, so as to pivot. The timer will then pop off the backplate. Fitting the new one is a reversal - just locate the 2 tabs on the top opposite to the screw holes, and pivot down from the top and inwards until you feel the pins locate with almost a click. Beware, there will be live 240 here. Isolate the CH system first.