Converting old CH controller to standard UK back plate

[Matt1984]

Hello,

I have finally got around to replacing my antiquated central heating controller and want to install a new digital one.

My old model is a RANDALL 102 and i want to wire in a new UK standard back plate that i can use with a new controller.

My CH system is one with a hot water tank and the old controller allowed you to have either just the hot water on or both the hot water and heating.

I have removed the old controller and am faced with 7 wires.

There are two 3 core cables and a single red wire.

One of the cables is clearly from the mains L N and Earth

I'm assuming the other cable is from the boiler?

The single red wire could be from an old unused room thermostat but i'm not sure?

If anybody could shed some light on which wire needs to go where i would really appreciate it. If it would help i could upload a video to show exactly what i've got.

Many thanks,

Matt

 

[stem]

Unfortunately, telling us the number of cores and colours of the wires is meaningless as they would have been chosen according to the personal preferences of the installer, and the physical layout of the various parts of the heating system. What we need to know is what is connected to each of the wires at the other end. There are two ways to do this. One is to trace where they go and see what is physically connected to each one at the other end. The second way is to tell us what terminals they were each connected to at the original programmer. Where there is more than one wire of the same colour you will need to differentiate between them.

We will also need to know the make and model of your new programmer, although the backplane is the same, not all programmers use the same terminals for the same purpose.

It sounds like the plumbing system you have is a what is known as a gravity fed system, where only the boiler comes on to heat the hot water, and the boiler and the pump come on when you want to have hot water and central heating. [ie there are no motorised valves controlling the functions] If so, please check that your new programmer is suitable for use with a gravity system. Not all are.

The Randall 102 wiring is:

Terminal 1 = Live to Boiler
Terminal 2 = Live to Pump
Terminal 3 = Live supply to switches, requires link to 'Terminal 6' (Live)
Terminal 4 = Earth(s)
Terminal 5 = Neutral(s)
Terminal 6 = Live Supply from Fused Connection Unit

When you have identified each wire, it's then a matter of working out the corresponding connection at the new programmer, which its instructions will tell you. You may or may not need the external wired link for your new programmer. Some do, some already have it internally.

If you find it difficult to work out, you can provide details of your new programmer, and tell us what terminals each of the original wires went to, and someone will then be able to tell you where they need to go now.

 

[Matt1984]

Hello and thank you for your speedy reply!

The new controller is a FLOMASTA 25902SX TWO CHANNEL PROGRAMMER

Fortunately i did note down the old connections before I took the old one off:

Connection 1 - Single Red Wire
Connection 2 - Red wire from boiler cable
Connection 3 - Jumper wire to connection 6
Connection 4 - Both earth wires
Connection 5 - Both Black wires
Connection 6 - Red wire from mains cable

I hope that makes sense? Apologies for my cluelessness!

Thank you very much for offering to help.

Matt

 

[stem]

OK good.

Connection 1 - Single Red Wire (Live to Boiler) = Flomasta 3
Connection 2 - Red wire from boiler cable (Live to Pump) = Flomasta 4

Connection 4 - Both earth wires (Earths - Self explanatory)
Connection 5 - Both Black wires (Neutrals) = Flomasta N
Connection 6 - Red wire from mains cable (Live) = Flomasta L

No need for any terminals to be linked the Flomasta does this internally.

This unit can be set for gravity hot water systems in the installer menu.

 

[Matt1984]

Thank you so much!

I'll give it a go this afternoon and report back...

Matt

 

[stem]

Thanks, look forward to hearing how you get on. BTW the wire you refer to as the 'boiler cable', based on where it was connected to the Randall, is actually the wire going to the pump. I haven't changed your description though, because it was the wording you had used to identify it.

 

[Matt1984]

It's working!

Brilliant, thank you.