Replacing Randall 4033 programmer

[Graham Mansbridge]

I would very much appreciate some advice on replacing my programmer that has stopped working after 33 years

My set up is as follows:

Glow worm spacesaver mk2 boiler

Hot water tank with 2 motorised valves

Randall 4033 wired as per diagram

Thermostat in another room


I have read a lot of other 4033 replacement stories here but none seem to be wired like mine.

At present the HW and CH will only work together as there is no independent control on the 4033. From what I have read here, the presence of 2 motorised valves may mean independent control is possible with a new programmer. Most I have seen have the same 8 terminals like the 4033 but if I just map the connections using the wiring diagrams I presume I will still have no independent HW and CH control.

I am guessing that all I need to know is how the current wiring diagram would differ if the 4033 had independent HW and CH control. Once I know that I should be able to map the wires on a new programmer (what ever I decide to get). Any advice would be greatly appreciated

And on that subject of programmers any recommendations would also be appreciated

 

[flameport]

Two valves and the wiring you have should already mean independent control is possible - it's just not possible with the 4033 due to how it's made, both CH and HW have to be set to the same times.

Wiring for pretty much any other 2 channel programmer is the same - permanent power L,N,E which is 6,7,8 on the 4033,
CH ON which is 2 on the 4033,
HW ON which is 4 on the 4033.
Terminal 1 and the connection between it and 6 (L) is already installed internally on most new programmers so won't be required.
The two Off terminals 3&5 are not needed now, and won't be needed on a new programmer either.

Wiring for a new programmer is just moving the wires from the old into the appropriate terminals in the new one.
You will need to keep the link between the red/brown wires from the C&D cables as you have now.

 

[Graham Mansbridge]

Many thanks for your speedy reply. So I just need to dispense with the 1 to 6 link and the rest stays the same.

I was thinking about a Hive. The terminal mapping looks straight forward enough thanks to your advice but I would have to disconnect the thermostat in the hall. Just to check - will this change anything re the wiring of the programmer or is the stat just wired to the connection box in the airing cupboard that controls the valves meaning I have to disconnect from there

 

[flameport]

The thermostat won't affect the programmer wiring at all.
If using the Hive, it's L,N,E and 3 for HW On, 4 for CH On. 1&2 not used.

The existing thermostat will need to be removed and most importantly the two wires connected to the switch contacts linked together permanently (equivalent to having the the thermostat permanently on). If this isn't done, the heating will not work.
That can be done at the thermostat position, or far better by locating the thermostat wires in the connection box, disconnecting them completely and installing a link between the two terminals instead.
Note that many old thermostats also have a neutral wire - this must be disconnected and NOT connected to anything.

 

[Graham Mansbridge]

Brilliant. Many thanks for your help