Potterton Ep2002 to TADO V3+

[Johntheo5]

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.

Have a look at the model number, and also ensure there are 3 pipes to the valve.

 

[polyfiller]

Yes it has 3 pipes to the valve. I fitted it last week...old actuator had died and the old valve was a bit stiff.

 

[Johntheo5]

Can you switch on the CH and HW at the programmer, then ensure the CH is calling for heat but the cylinder stat isn't, turn it down if its calling, Valve will/should work fine, it will move to the CH only position and the boiler will continue to fire from the MPV orange wire, next switch off the HW at the programmer, the valve should move back to mid position but the boiler should stop firing as there is now no power to the cylinder stat to supply power to the boiler via the cyl stat satisfied terminal and there is no HW OFF supply?.

Did that new valve replace something similar like a danfoss/honeywell/drayton etc or was the old MPV a Potterton like the MSV 322 or MSV 328?.

 

[polyfiller]

Johntheo .... thanks for the test suggestions. With the Potterton installed, am getting some strange results.....

Per your test - CH & HW on on controller, HW stat NOT calling, CH stat calling, bolier fires Y valve in mid position. Then turn off HW at controller, CH stat still calling, boiler still firing - so not as you suggested above. Then turn down CH stat, and boiler stops firing.

also tried this if it helps ....
1) Turn CH & HW on on Potterton, both stats set to call for heat = Y valve in mid position - so good
2) With CH & HW still on, turn off HW stat, valve goes to CH position - so good.
3) Turn HW stat back on to call for heat - valve stays in CH position - so NOT good.... not going back to mid position.
4) Turn CH & HW off & then on again to return valve to mid position ... then ....
5) Turn CH stat off and valve goes from mid position to the CH postion --- so NOT good.
6) Turn CH stat back on, valve stays in CH position, despite both stats calling for heat ... so NOT good becaue valve not returning to mid position.

The new valve replaced a Myson which replaced a prior Myson head which went bad. I moved to the DANFOS valve and head because the original Myson valve was stiff and caused the last head replacement to fail after only 18 months or so. Definitely a Y valve with ports A, B and AB. When initially switching both CH & HW on, it goes to mid position and both pipes to cylinder and radiators get hot.

 

[Johntheo5]

Thanks, will try to digest this later.

The model number for Danfoss mid position valve is HSA3 087N6587, it also states it has a auxiliary switch SPST which i assume supplies power to the boiler via a purple wire on CH only, doesnt mention the two internal switches but I suppose this is normal.
You might try and check this model number against your valve.

 

[Johntheo5]

.
Per your test - CH & HW on on controller, HW stat NOT calling, CH stat calling, bolier fires Y valve in mid position. Then turn off HW at controller, CH stat still calling, boiler still firing - so not as you suggested above. Then turn down CH stat, and boiler stops firing.

Try and figure this out bit by bit since I'm a "mechanical" man.
With no HW OFF with CH calling but the HW switched off then the valve should remain in mid position but the boiler should not fire IMO.

 

[polyfiller]

Progress .....I used the first wiring diagram you posted (colour one) to work out what should be connected where. I then traced all wires from the Potterton ep2002 to the wiring center and to the room stat and labelled them. I then worked out which wire SHOULD have been in terminal 1 (HWOFF) and connected that to 1 and to the correct terminal for the Y valve. Previously that wire was permanently live. Been like that since house was built (been here 27 years). Now just test the potterton and valve moves to all 3 positions and back again depending which combination of room/cylinder stat is calling for heat. Thank you so much for your help and especially for that first diagram...a numpty like me was able to work it out.

 

[Johntheo5]

Well done.

 

[RandomGrinch]

Well done.

Well, that's an unusual one for me.
If it 'ain't broke, Do fix it!