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Rick Ridley
Rick Ridley, UK Heating Engineer
Category: UK Plumbing
Satisfied Customers: 2708
Experience:  30 Years on the tools, now retired, Ex CORGI
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Vaillant ecoTEC plus 831 boiler is in and running the house

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Vaillant ecoTEC plus 831 boiler is in and running the house heating and water.
Control of heating is only by radiator valves with the standard analogue central heating timer on the boiler.

I want to add a wireless thermostat for the house.
I also want to add two new heating zones - one to a radiator in an annexe, controlled by another wireless stat - the other to a digistat controlled h/x in the same building.

I think I know how to do this - but can anyone provide me with advice on how they would set up the plumbing and wiring to do this?

One particular question linked to this - these are the instructions for the boiler:

Does the jumper wire on terminal 3 and 4 needs removing and which terminal do you connect the switch live's to from 2 zone valves to fire the boiler on heat demand and turn it off when the stats are happy?

Thanks for your time
Hi I am Rick, UK Plumber, and I specialize on Boiler problems, can you tell me what motor valves or valve you have at the moment if any, terminals 3 and 4 are for external boiler controls so this is where you would wire the switched lives from you new zone valves, but if you all ready have valves where do they link to at the moment? Rick
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Customer: replied 5 years ago.
Don't have any valves at present, just the installed c/h system - intend to buy 3 x Honeywell 2-port valves - one for the house system and one for each system outside.
The plan is to tap into the feed and return 22mm c/h pipes beside the boiler - run these out to the annex - separate this into two zones, one for radiator controlled by new wireless stat, one for h/x controlled by digistat. And at the same time add a wireless stat to the house circuit.
I need to know if this is the best way - and how to do the wiring?
OK so I can fully understand your system, how do you control your hot water at the moment, and what you have said so far sounds OK, Rick
Customer: replied 5 years ago.
Hot water and c/h both from the Vaillant boiler - tap hot water on demand - c/h has a switch (off/on/auto) and the auto is controlled by the analogue 24hr timer - essentially a clock with pins around it that are either in or out to determine on or off - and each radiator has a valve on it that ranges from 0 to 5 to control the heat in the room - which is why I want to add the thermostat at the same time as the extra systems.
Ah you are talking the Combi version, I had assumed otherwise, with a combi it is not quite so easy, you cannot just tee into the flow and return, you will need to cut the flow and route it to the three motor valves and then one of the valves will be connected back to the house flow, and similar with the returns, the heating part of the boiler will then be controlled from the three new valves to terminal 4, Rick
Customer: replied 5 years ago.
That's what I thought, I believe it's an S-Plan Plus system.
This is how I see it - a tee into the flow pipe, with a 2-part motorised valve for the house system after this - then from the tee the pipe goes out to the annexe - then another tee - one to the pipework and a 2-part motorised valve for the radiator - the other part of the tee to another 2-part motorised valve for the heat exchanger pipework - then pipe returns all tee'd back together to the house and tee'd into the original return pipe.
Is this right - and can you help with a wiring plan specific to my boiler?
Yes I think you have got it there, the important thing to remember to remove any doubts is that the main flow from the boiler stays on the inlet side of all of the valves as many as you like, as for wiring this is straightforward, each zone has a programmer then a stat (or programmable stat) this then sends live to the brown wire on the respective valve, when the valve opens the grey wire sends power to terminal "4" on the boiler (remove link 3 to 4) all of the valves have the grey wires connected and all of the orange wires have permanent live connected, remember to only take power from the same source as the boiler, Rick
Customer: replied 5 years ago.
Rick, thanks for your help - I just need to check something and if I don't have any more questions around this I'll come back and click Accept Answer - hope that's ok, and thanks again.
No problem, in case you were wondering the boiler has an automatic built in by pass valve, the only other point is there is no need to remove the built in clock just set it to 24 hours, Rick
Customer: replied 5 years ago.
Rick, there is one more thing, looking at this diagram, which number terminal in my boiler does the Lr connect to?
If the digram is wrong for my boiler, can you tell me what's wrong and in particular what terminals of my boiler relate to those in that part of the picture.
The ideal place to pick up your power for your controls is terminals 3 4 and 5, (3) is permanent live out to your controls and end switches on the motor valves, (4) is connected only to the other wire of the end switches, and (5) is neutral for your controls, (4) is the important connector this one fires the boiler, Rick
Customer: replied 5 years ago.
Rick, so based on this wiring diagram from the boiler installation manual, where would I connect Lr from the other diagram?
Lr you will see is the orange wires from the motor valves Lr is the same as (4),,, Ls is the same as (3),,, Ns is the same as (5), Rick
Customer: replied 5 years ago.
It's making a lot of sense now Rick - one thing - having 2 thermostats and 1 digistat all calling on the boiler through the same connections won't be a problem?
I understand that if one stat is calling on it and another also calls, then the valve for the second stat just opens and the hot water circulates - but what happens when one stat says to stop whilst another is wanting it to run - why doesn't the boiler stop?
because the motor valve of the stat that is still calling is open and the end switch is closed giving power to the boiler, Rick
Customer: replied 5 years ago.
Thanks Rick, one more thing to check in my manual, and if that's ok I'll click Accept Answer - you have been a great help.
OK wait to hear, Rick
Customer: replied 5 years ago.
Thanks Rick, that's everything covered - paid.

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