Switchmaster 805 dial not rotating

[hellotaral]

Hi all,

I am totally new to this forum. But I am hoping that I will surely get an answer to my questions. I just bought the house and it has
Potterton Boiler system
Switchmaster 805 control
Teddington thermostate

Boiler system works manually and via thermostat but dialer on the 805 does not rotate automatically. So to start, I had to manually turn the knob on the boiler. Keeping thermostat to 0, I can get hot water. Keeping thermostat to desired temp, turning the knob ON gives hot water and CH. As winter is on its way, I have to fix this issue.
I am looking at various forums and it shows the replacement side but I am not sure if my Switchmaster 805 is faulty or wiring is faulty? I am willing to buy new timer if I can confirm that it will work. So couple of questions,
How do I confirm that my Switchmaster 805 works?
What is the function of Randall box underneath switchmaster 805?
Will replacement of compatible Switchmaster work in this condition?
Can someone recommend replacement for this please? (So far I found Channelplus H21XL)

I would be grateful if someone can advise

Thanks
TK

Untitled

• hellotaral
• 13 Sep 2013
• 1

Untitled

• hellotaral
• 13 Sep 2013
• 1

Untitled

• hellotaral
• 13 Sep 2013
• 1

 

[Tom1981]

Any dual channel programmer will replace it.
The box underneath it a wiring centre for your Central Heating

Your programmer is going to be pushing 30 years old, so it can't hurt to change it

Depending on the design of the system it can be setup to run water and heating independent of each other, if its a gravity system with no zone valve then its a simple case of linking the channels allowing your thermostat to control your pump during a on period.

 

[OwainDIYer]

Apart from checking that permanent live and neutral are present on the L and N terminals at the timer, there's not a lot to check.

If it's not ticking the motor's jammed or faulty.

The Randall box is just a junction box where all the wires come together.

Horstman equivalents and wiring terminals listed at
http://www.horstmann.co.uk/downloads/electronicdocuments/central-heating/wiringguide.pdf

 

[hellotaral]

Thanks Tom1981 and OwainDIYer for your quick replies.

Really useful to me as I have just started doing DIY first time in our new home.

If I buy Channelplus H21XL and replace it with alteration of wire, I think that will fix my issue?

Thanks