Potterton EP2002 programmer replacement for Tado extension kit - wiring issues

[Grak]

Hi All,

I'm really hoping someone will be able to help me with the wiring situation on the backplate of the Potterton as it's a non standard one and as such will need to swap this one out for the Tado backplate.

The trouble I'm having is that there's no hep available for what working is needed as part of the swap over.

I've taken pics of the Potterton plate with wiring in situ still and images of the rear of both device fronts to try to assist in which wires need to be transferred to the Atari backplate.

Thanks everyone in advance too but I have tried to find a solution by searching but can't see Tado anywhere only Hive!

Keith

 

[stem]

The EP is a bit unusual because it is a Programmer and Wiring Centre combined. The terminals marked A B C & D are just provided for convenient use by the installer. They are not connected to the programmer functions in anyway. They are just connectors.

In your photo, it looks as if only A and B are used, so all of the wires from A need to be removed from the EP and then reconnected together as they are now. I usually use a screw terminal and tuck it in the back box. Likewise all of the wires in B need to be removed from the EP and then reconnected together as they are now.

N and L obviously are the 230v supply and should go to the Tado N & L respectively.

The earths need to be connected together, and should also include a wire to the back box in the wall if it is metal.

You are now left with the heating control wires, you can identify the function of each terminal from the EP you posted. You can ignore terminal 5 and remove the link between it and L, because the Tado has this internally. The function of the remaining wires in 1, 3 and 4 can be determined from the diagram on the EP you posted.



Then it is a matter of moving the aforesaid wires presently in 1, 3 and 4 to the terminals at the Tado that have the same function again as per your photo. You are fortunate. They are the same. Make sure the jumper is in position 2.



HW off = 1
HW on = 3
CH on = 4

 

[ericmark]

Question one has to be what type of boiler? is the boiler going to be controlled by the programmer or return water temperature? I think the Tado is OpenTherm, but not sure.

So if swapping from on/off control to modulating control then likely the programmer will need new wires to boiler.

Old boilers and systems were digital they simply switch on/off, new systems are analogue the flame height varies and the flow rate through the radiators vary which means it uses less energy and has very little hysteresis. I am told Tado is very like EvoHome in that the thermostatic radiator valve (TRV) head is wifi linked to the thermostat (really a hub) which in turn tells the boiler how much heat is required, and modulates it (turns it down) as required. However they can be configured to switch boiler on/off if the boiler is the old type.

Where a room wall mounted thermostat is used then it can either control boiler directly and that room only is kept to right temperature, or it can be used to stop the boiler cycling as we get warmer weather, former is fitted in main room, latter is fitted in the coldest down stairs room with no outside door or other forms of heating.

So before knowing how to wire, you need to know what you want it to do. Both old and new have two relays on for domestic hot water and one for central heating but the Tado will not require the old thermostat, and so this needs identifying normally found in the wiring centre and it seems the old programmer has the wiring centre built in, normally they are with the hot water tank.

I am not sure of physical sizes, but I would be looking at an adaptable box to replace the old programmer and then mount the Tado on the top of it. The old unit has volt free contacts for the central heating, the tado does not, it may not matter, but you will need to test, if the boiler control is 24 volt which was common with old boilers then you can't use that Tado, I know Nest do a volt free unit, not sure on EvoHome, and Hive is not volt free.

 

[ericmark]

Well spotted stem didn't see link wire.

 

[Grak]

Thank you so much gents for your efforts and thoughts too. At least I have something to go on to swap the plates over now. Will give an update when I get some free time to swap over.
Regards and Best Wishes
Keith