Drayton Wiser & Baxi - Opentherm Installation Issues

[Ramaya]

Hi, I've joined because I have a lot of trouble with trying to make my new boiler work with the Opentherm interface and thought someone with more experience than me could help.

Equipment:
Drayton Wiser - Single Channel Programmer with Opentherm module.
Baxi 836 Combi boiler with Opentherm.

Situation:

• In order to make things simpler, I have removed all smart TRV's and only kept the room digital thermostat.
• Old set up had a traditional dial room thermostat which has been removed and the wires spliced to send a constant signal to the programmer (Live to Live, Neutral to Neutral), picture attached.
• The Wiser Programmer was a straight swap with the new Wiser terminal and the Opentherm wires have been connected with the wires sending a signal to the boiler.

Problem:
Once the boiler and controller are switched on the boiler constantly runs in full power without modulating and with the boiler controls being completely locked out, this is happening regardless if there is a call for heating from the programmer or not (Heating green light on/off). I can not switch off the heating via the app even by reducing the temperatures. The only way of stopping it is cutting the power to the boiler. Currently I do not want to switch on the boiler as I have no way of stopping it from running at full temperature and I am scared I will damage it as I have already forced closed it a couple of times when I realised this was happening.

Installation:
A Baxi engineer installed the boiler and altered the controls. He claims it has been wired correctly for Opentherm, (I think it is not). I would like to note that the Drayton Wiser System was working fine with my previous boiler albeit without the Opentherm modulation.

Troubleshooting so far:
- Checked if app is set as Opentherm
- Asked drayton wiser to run diagnostics

Is there a kind soul that can maybe help me troubleshot this? Attached a few photos of the situation.

I phoned one of the Drayton wiser "approved" installers from their website and he basically said it is like black art and that last time he had to deal with something like that he spend 20hours to resolve it..

 

[ianmcd]

Old set up had a traditional dial room thermostat which has been removed and the wires spliced to send a constant signal to the programmer (Live to Live, Neutral to Neutral), picture attached.

take a proper look at what you have done with the old room stat,black does not mean neutral in a heating system

 

[Ramaya]

take a proper look at what you have done with the old room stat,black does not mean neutral in a heating system

Hi thanks, just to make it clear I didn’t do any of these connections the Baxi engineer did. Could you maybe offer me a little more guidance on what do you mean? Is there a certain way the should be wired?

 

[ianmcd]

Hi thanks, just to make it clear I didn’t do any of these connections the Baxi engineer did. Could you maybe offer me a little more guidance on what do you mean? Is there a certain way the should be wired?

what make and model was the origional thermostat

 

[oldbutnotdead]

First (easy) test is to set the Wiser controller to Relay control (in the options menu- choices are Opentherm or relay) and see what happens (ie does boiler respond to the Wiser controller).
Second test is remove the Wiser controller from the backplate, disconnect one (or both) of the Opentherm links (the flex going into the terminal block) then power up the boiler and see what happens.
The results will determine the next steps to take...

 

[Ramaya]

First (easy) test is to set the Wiser controller to Relay control (in the options menu- choices are Opentherm or relay) and see what happens (ie does boiler respond to the Wiser controller).
Second test is remove the Wiser controller from the backplate, disconnect one (or both) of the Opentherm links (the flex going into the terminal block) then power up the boiler and see what happens.
The results will determine the next steps to take...

Thank you. I will do these and report back

 

[Ramaya]

what make and model was the origional thermostat

Drayton programmer
Siemens wall dial thermostat

 

[muggles]

Would be good to see how this is connected inside the boiler, but as a rule Baxi boilers don't like single channel OpenTherm controllers. They've cocked up the implementation and so even with a combi you need an OT controller capable of controlling hot water as well as heating. To compound the issue I don't think Wiser's OT works properly either...I know they've had some issues controlling system boilers

 

[Ramaya]

Would be good to see how this is connected inside the boiler, but as a rule Baxi boilers don't like single channel OpenTherm controllers. They've cocked up the implementation and so even with a combi you need an OT controller capable of controlling hot water as well as heating. To compound the issue I don't think Wiser's OT works properly either...I know they've had some issues controlling system boilers

Yes I noticed that there is no way to control the hot water output. Would I be better of with a different system? What would be a suggestion for the Baxi?

Inside the boiler the Opentherm is just connected to the top two cables on the terminal

 

[muggles]

Nest works, and so does Honeywell T6

 

[Ramaya]

Found the issue after opening the ECU the installer had forgotten the testing loop in which was just making the boiler fire up at max all the time.

 

[oldbutnotdead]

Found the issue after opening the ECU the installer had forgotten the testing loop in which was just making the boiler fire up at max all the time.

That was my next question- slight concern is I'm not sure if the front cover is part of the room seal on that boiler.....

 

[Ramaya]

That was my next question- slight concern is I'm not sure if the front cover is part of the room seal on that boiler.....

Not sure what you mean with your reply.

 

[oldbutnotdead]

The front covers on many boilers are part of the room seal- that means it keeps combustion products going up the flue rather than into your kitchen. The manual mentions seals on that cover....with luck someone who knows will pop up and confirm or deny.

 

[muggles]

Not sure what you mean with your reply.

The front cover of your boiler forms the safety room seal and should only be removed & refitted by someone who is Gas Safe Registered and can carry out the required safety checks on completion of works