Connecting Drayton Single Channel Wireless Receiver (Smart Heating) to Vaillant Ecotec Plus 837

[SoylentRed]

Hi all,

Hopefully someone can help:

I've bought the Drayton Wiser multi-zone kit 1 (single channel) and need to wire the wireless receiver to a Vaillant Ecotec Plus 837 combi boiler.

The boiler is currently connected to a manual thermostat (Siemens RAA20) by a live and neutral. I assume these connect to 3 & 4 on the boiler, though I'm a little confused as the neutral is black and the live red at the stat end, but where it connects to the 230V on the boiler it's blue and brown? Is there potentially a connection in the middle?

From my research am I right in thinking I can just connect the wireless receiver from L/N/3/4 on the boiler to L/N/1 (common)/3(Heating on) on the receiver using a new heat resistant 4 core?

Can I leave the thermostat connection in place to use as an override and double up the wires connected to 3 & 4 on the boiler? (1 wire from stat and 1 from receiver on each). My concern here is that the two existing cables are using up the only two cable slots inside the power case, so I'm not sure where I would run a third cable while preserving the integrity of the case.

If I wanted to remove the manual thermostat what would be the process for making it safe, as the wiring runs through the house so no chance of pulling the cable out.

Thanks in advance!

 

[ericmark]

It depends on what you want to do? I think there are conversion modules to link the Wiser OpenTherm to Valiant system. But one could also use on/off control.

The single channel Wiser hub is volt free, so it can be powered from another source, personally I would not want to do that, as my boiler is battery backed, so want the thermostat either battery or UPS supplied, and would advise you consider the future and keep all parts of central heating off the same supply.

I don't know if you can remove the covers over the connections on Valiant, some boilers one needs to be gas safe to remove them, yes seems stupid idea, as often boilers wired by electricians, and with an EICR the inspector has to inspect, but for reasons best known to the gas people, some boilers have the connections in a room sealed section.

If the wires change colour, I would guess there is a motorised valve. The old idea was the thermostat controls the valve, and then the valve controls the boiler, with a combi boiler not required, but may be a junction box where the valve once was.

 

[SoylentRed]

Thanks @ericmark. The boiler is about 17 years old so I'm thinking the easiest and cheapest method available. We will be looking to swap the combi for a system boiler when it eventually packs in.

The goal is to control the boiler on/off via the Drayton app and controls. As I understand it would be a case of if one rad is under temperature it would make an on call to the boiler until all rads are at temp or the system is scheduled off.

I read the boiler manual in advance and couldn't see anything about needing to be a competent engineer to remove the cover.

Noted regarding the possible valve. The house is full of bodgery from the previous landlord owner. Is there a possibility that disconnecting the stat and valve could interfere with another circuit in series?

I don't mind leaving the stat in place as it would be a useful override if we go on holiday and a smart TRV battery fails and causes it to call for heat all day, but that leaves the question of how to route a third cable into that wiring compartment when there's only two cable slots.

 

[ericmark]

I have two thermostats in parallel, which means if the Nest or Wiser fails, the other will allow the house to be heated, but it was not done with that in mind, it was because the hall where Nest is, cools too slowly, so the living room would get cold before heating cut in again. But the living room has an open fire, so if lit without the hall thermostat, the rest of the house would get cold.

Wiser was not quite as expected, not the fault of Wiser, but where the radiators are. Late mother's house all radiators are on internal walls, and electronic TRV control worked very well, each room within 0.5°C of setting unless other heating like sun through windows lifted it up. In this house the oil boiler does not modulate, simple on/off, and the radiators are under windows, the problem is that means when the heating is not running, the radiator and TRV on the radiator is actually colder than the room.

Once the heating is running, the thermals in the room mean the TRV works A1, but it is that time when heating not needed every day, the TRV will get just a tad too cool and fire up the boiler when not required. So where the radiator is on an outside wall, it may be better using a wall thermostat to fire up the boiler.

So I have one Wiser wall thermostat and one Wiser linked TRV head, all the other TRV heads are programmable, but they will not fire the boiler.

 

[CountryFan]

Vaillant doesn't support open therm so no point taking that on board. My guess for the colour change is that the existing thermostat wiring goes to the FCU and is picked up using harmonised colouring now. You could disconnect 3&4 at the boiler and FCU accordingly and change the cable for 5 core heat resistant flex and piggyback LNE and then just the switching wires of live out and live return, not L and N as you previously called them. Yes the boiler forms part of the combustion circuit, however after reading a recent paragraph again in the gas regs, advise may have been given incorrectly previously.

 

[ericmark]

Vaillant doesn't support open therm so no point taking that on board.

Sorry, I thought these

allowed one to use OpenTherm, I stand corrected. I now note:-

To convert OpenTherm to a Vaillant system, you need a specific module like the Vaillant VR33 OpenTherm Module. This module acts as a bridge, allowing a compatible OpenTherm thermostat to communicate with a Vaillant boiler, enabling precise control and potential energy savings by modulating the boiler's output. However, be aware that using this module on a UK-market boiler might void your warranty, as the VR33 is primarily for other markets like the Netherlands.