Potterton Ep2002 to TADO V3+

[polyfiller]

Hi,
first post on here. I read some previous posts before buying TADO V3+ CH & HW control kit with the intention of replacing my old Potterton 2002. However .... upon inspection, the guidance given in other threads doesn't appear to line up to what I have ..... in other threads the suggested connection is;
Potterton TADO
1 > HW OFF
2 NOTHING
3 > HW ON
4 > CH ON
5 NOTHING

However in picture below of my Potterton I have no connection currently to 1 (HW OFF). Also I checked the vltages on the wires already connected and the live feed is actually to 5 on the Potterton which you can see is then jumpered back to Live. My system is Y valve pumped with an old Walstar Oil fired boiler. The Potterton is located right next to the boiler and there is a wiring centre in the airing cupboard next to the Y valve and pump. Any advice on how to handle the absence of wire on 1 ?

Thanks in advance for any advice.

 

[Johntheo5]

Can you programme the HW and CH to be on and off separately, if so then you need a "HW off" wire to the M.pos valve to drive it to the CH position if the HW is programmed off. If you left the HW programmed ON all the time then the cyl stat will provide the HW OFF to the M.pos valve when the cyl stat is satisfied. connecting L&5 might be a work around having to wire in the HW OFF or you may not have a HW OFF contact on your programmer.
Below is the "normal" Y plan schematic.

 

[polyfiller]

Thanks ... I can confirm that with the Potterton I can run the HW and CH separately. The diagram is a little overwhelming ... I'm trying to work it out. So maybe I should try and trace the connection between the grey wire in my junction box (which comes from Y valve) down to the Potterton back plate ?

 

[Johntheo5]

Yes, I would trace that wire as you suggest and just to be clear, its a mid position valve and not a diverter valve where you can have CH or HW but not both together?.

 

[polyfiller]

Correct - it id s mid position valve - I can have both CH & HW running together.

 

[Johntheo5]

I don't get that boiler wiring diagram as the switched live to the boiler comes from the mid position valve.

 

[RandomGrinch]

.. I can confirm that with the Potterton I can run the HW and CH separately

If the potterton wiring is working, why the need to change it?

Just connect the L's together including the extra wire currently in 5 on the Potterton.

N's > N
3 > Hot water On
4 > CH On

(+ add bridging wires between L and the commons on the Tado)

...and see how it works.
The type of system can be changed in the Tado configuration, if there are problems.

I don't get that boiler wiring diagram as the switched live to the boiler comes from the mid position valve.

Do you need to, if it currently works?

 

[Johntheo5]

Plenty of wiring diagrams here for this Potterton with its own MPV.

 

[CBW]

Are you sure it’s a mid position valve? Can you post photo of the valve?

 

[Johntheo5]

Apparently it is CBW, post #5, even though it doesn't specifically say that. If the Potterton MCP is similar to the "conventional" Honeywell or Drayton where the only way that they will drive the MCP to CH only without a HW OFF wire is if the CH &HW are allways programmed/timed to be on/off together, in which case the HW cylinder stat will supply the HW OFF via its satisfied terminal 2, the valve will then motor fully over to give CH only, if you switch off the HW then the valve will only motor and stay in mid position (via white wire) and will keep heating the cylinder with CH only required. Its strange but the Potterton schematic shows a HW OFF contact but seems to be optional?.

 

[Johntheo5]

Here are the PTT2 connections as per some other DIY post, wiring diagram from Potterton.

Terminal Symbol Function Wire Connect to
1 H HW On/Call Blue with sleeve Terminal 8
2 C HW Off/Satisfied Yellow Terminal 7
3 L Permanent Live Red Terminal 1
4 TL HW on Call from Programmer/Timer Brown Terminal 6
5 N Permanent Neutral Blue Terminal 2

 

[CBW]

Apparently it is CBW, post #5, even though it doesn't specifically say that.

Yeah I saw that but it doesn’t confirm much.

Here are the PTT2 connections as per some other DIY post, wiring diagram from Potterton.

Boiler is a wallstar oil fired as per post #1, which weirdly when I search comes up as a combi boiler.

 

[polyfiller]

Here is a picture of the Y valve...

 

[polyfiller]

I guess I can check for Y valve operation later by removing the actuator and checking it's movement with both CH and HW on. I'm pretty sure it is....with both on the HW stat does not trigger boiler off when temp reached and room status still calling for heat.

 

[CBW]

Here is a picture of the Y valve...
View attachment 303967

Hard to tell, but it doesn’t look like a 3 port valve. Can you do one where the pipework enters at allegedly port ab, so near the fire extinguisher