Central heating pump amd 3 way motorised valve problem

[Marmite]

I'm hoping there will be someone here who can help me with 2 problems i have.

The first problem is that my central heating and domestic hot water system are approx 30 years old. I had until recently an SMC controller pump which acted in 2 ways - it allowed water to run straight thorugh (when not powered) to the central heating pump which was below it and secondly when the SMC controller pump switched on it still allowed water straight to the central heating pump but also diverted water off to the side which went into my cylinder etc. I have recently removed the SMC controller pump because i have had a lot of trouble with it and getting replacement pumps was difficult and expensive. So what i have now is the following - Water from the boiler arrives in airing cupboard and i have fitted a conventional central heating pump, below the pump is a three way motorised valve, the valve diverts water to either the cylinder or the radiators or both. The sytem works fine when i operate the 3 way valve manually because its not wired in yet (see problem 2) however i have an issue with the electrics.

Because my system used to have 2 pumps i have 2 live feeds in the airing cupboard, which live feed do i connect the new pump to so that it runs when i select either hot water or central heating? At the moment i have it connected to the hot water feed so if i want central heating i have to have hot water too. If i want central heating the pump wont energise so i have to have central heating and hot water together to get the pump to run.

Second problem

I have a 5 way wiring block in the airing cupboard and it is wired in the following way.

Terminal 1: Central heating pump (new pump) neutral
Terminal 2: Nothing connected but used to be a live for old Central heating pump when 2 pumps were fitted
Terminal 3: Cylinder thermostat neutral
Terminal 4: Cylinder thermostat live
Terminal 5: Live feed for new cental heating pump but used to be live feed for SMC controller pump (DHW)

How would i wire in the 3 way valve? The valve is a drayton mid position valve model MAI/679-3.

The valve has 5 wires coloured white, grey, orange, green/yellow, blue.

From my research i think i figured out the orange wire shares the same live feed as the pump, and the blue shares the neutral from the pump too. Green/yellow is earth but where do i connect the wires on the wiring block?

 

[thereisawizza]

When taking out a SMC/comet set-up, disconnect it all and start from scratch with conventional Y-plan wiring schematic, obv allowing for pump-overrun if req.

 

[diamondgas]

If your boiler does not have a pump over-run fitted then you connect your pump and boiler to the orange & HW demand from your programmer. The white is connected to your room thermostat switched live, your grey is connected to your cylinder stat satisfied (n/o). and also with the orange is the cylinder stat calling (n/c)

Do you have a room thermostat?

If not then link the white and grey to the cylinder stat n/o, satisfied ... Your cylinder stat DOES NOT have a neutral!!

 

[diamondgas]

Okay just realised our second problem ....... lets see if I can help here..........

Terminal 1 = Neutral
Terminal 2 = White (Room stat calling) (Heating on)
Terminal 3 = Grey (Now this is the dodgy one) Cyl stats don't have neutrals so I'm assuming this is the 'satisfied' switch live!
Terminal 4 = (To Cyl Stat)
Terminal 5 = Orange and new pump and boiler suply (Hot Water on)

 

[missplumb]

you say the heaing flow comes into the cupboard and into the new pump, below that there is a 3 way valve? is that on the same pipe? the pump should go before the valve not after it. that way it pumps around the heating circuit and hotwater circuit. and if i remeber , if the valve is mid position then you will always get hot water when the heating is on as it would only revert to mid position.

 

[diamondgas]

you say the heating flow comes into the cupboard and into the new pump, below that there is a 3 way valve? is that on the same pipe? the pump should go before the valve not after it. that way it pumps around the heating circuit and hot water circuit. and if i remember , if the valve is mid position then you will always get hot water when the heating is on as it would only revert to mid position.

Hi Missplumb,
You are right about the positioning of the pump in association to the diverter, however if fitted on the return circuit they will be the other way around. Regards the diverter valve there are two types, 'W' plan & 'Y' plan. The 'W' plan valve gives you either or in regards hot water or heating. In Rest it'll supply hot water, when energised diverted to central heating. The 'Y'plan mid position valve will suply at rest hot water, with a call for heating from the room stat (White) it moves to mid, supplying both water and heating then once the water is satisfied, cylinder stat n/o satisfied(grey), it moves to heating only. The orange from the diverter then suppliers the power to the pump and boiler.

Hope that has been of help....