Vaillant ecotec plus 418 Boiler wiring problem

[Deano sparky]

Hi guys go easy on me 1st post. Moved into a new home and the heating system is a vaillant eco Tec plus 418 with a wireless programmable stat (vrt 392f) and 2 X 2 port zone valves one for HW & other for CH. Since I moved in the system has not been working as a heating system should. I have replaced what I thought was the problem the programmer with a new VRT 350f and also replaced the CH zone valve as the lever was knackered and was staying open all the time even with power off. Now when I switch the boiler on and off both valves open and close as they should when power disconnected and the HW valve seems to work correct with the cylinder stat. But the CH valve seem to stay open all the time soon as power is switched on. I have disconnected the receiver from the BUS to eliminate the programmer being an issue and the valve still stayed open. On further investigation I have found that there is a permanent live feeding the brown of the CH valve in the wiring centre which is obviously keeping it open all the time. How is this supposed to be switched with a wireless programmer/stat. In the boiler wiring centre I have a switch feed in terminal 4 which is controlled by the cylinder stat and a link between 3&4 is this correct? Any help would be much appreciated before I get vaillant in.

 

[Deleted member 267285]

None of that isn’t linked to the immersion heater (these have their own thermostat), so please stop calling it an immersion stat - it’s a cylinder thermostat/stat. 3 and 4 are Live and switched respectively, usually for room thermostat. So the blue wire goes to the cylinder thermostat? Also where does the red wire in your wiring center go to? Grey are normally permanent live and switched with the orange wire in 2 ports.

Also make sure the boiler is tested afterwards, I’m sure they have a case seal that forms part of the combustion circuit.

 

[Deano sparky]

Hi thanks for your reply have updated Thread you are correct it is a cylinder stat . The blue wire in terminal 4 becomes live when the cylinder stat activates the HW valve. The red from the wiring centre goes to another mess of a wiring centre behind the boiler. Picture below. I'm guessing I'm gonna have to remove at least a tile to get to it. So the CH zone valve should not be open constantly regardless if it's a wireless stat or not.

 

[Deleted member 267285]

So the CH zone valve should not be open constantly regardless if it's a wireless stat or not.

No it shouldn’t. As I said 4 is switch live to room stat generally, but would probably be considered pump live in your setup.

 

[picasso]

Where is the vr65 ? your boiler is being controlled by the vaillant ebus and needs an interface between the ebus and 240v 2 port valves.

 

[Deano sparky]

I don't believe it has one. All I have is the vrt350f and a receiver which connects to the BUS inside the boiler. So your saying I should have a vr65? Would this replace the wiring centre which is next to the zone valves. Would make sense why it's never worked properly.

 

[fixitflav]

On further investigation I have found that there is a permanent live feeding the brown of the CH valve in the wiring centre which is obviously keeping it open all the time.

There is a permanent live to the microswitch in each valve, which when closed (when the valve is fully open) starts the boiler and pump. The live to the valve actuator comes from the corresponding stat.

 

[Deano sparky]

Yes I believe the grey is the permanent feed and the orange is used to make the circuit. The problem I have is that there is a permanent feed feeding the brown core which is supposed to be the switch live from the stat. But the stat is wireless and there is no interface so not sure where this live feed is coming from. Looks like Micky mouse has installed the system.

 

[fixitflav]

Yes I believe the grey is the permanent feed and the orange is used to make the circuit. The problem I have is that there is a permanent feed feeding the brown core which is supposed to be the switch live from the stat. But the stat is wireless and there is no interface so not sure where this live feed is coming from. Looks like Micky mouse has installed the system.

OK, see what you mean. I would assume the wireless stat talks to a receiver which activates a relay to power the valve, or something along those lines. In that case it could be the relay stuck closed.

 

[Deano sparky]

The boiler display is now showing F.24 and the vrt350f is displaying heat generator fault so the programmer and boiler are talking to each other but think the system needs the vr65 for the wireless stat to be able to operate the heating.

 

[fixitflav]

The boiler display is now showing F.24 and the vrt350f is displaying heat generator fault so the programmer and boiler are talking to each other but think the system needs the vr65 for the wireless stat to be able to operate the heating.

Dunno, sorry, I was just commenting on the valve live wire issue.

 

[picasso]

Here is a vr66 that would do ya....

Preowned Vaillant VRT 350F Wireless Thermostat and VR66 Wiring Centre | eBay

 

[Deano sparky]

Cheers picasso much appreciated. Where do you normally install these? Is it best next to the boiler or can it be used as a wiring centre near the 2 X zone valves,pump and cylinder?

 

[Deano sparky]

Okay done some research and it looks like it has never been installed properly. Can't believe they never installed the VR66 and expected it to work properly. There is no way of switching the heating on and off without it. The CH zone valve is just constantly open calling for heat everytime the boiler is switched on which I'm guessing is why it burnt out. I have found this diagram for the VR66 which makes perfect sense. My only question that I'm not sure about is where does the pump get wired into. Does it connect into the boiler and linked with the zone valves? Any help would be much appreciated

 

[Deleted member 267285]

The pump is already wired at boiler pcb isn’t it?