The Efficient Home Forum

Hi folks. Sorry if this is a basic problem but I cannot find any info on it. I have just purchased and installed the honeywell evohome system. I have some HR92 valves, opentherm bridge R8810 and the evohome controller.
My problem is that I cannot bind the opentherm bridge to the controller as i cannot put the bridge into bind mode. It's connected to a vokera vision 30c boiler to the opentherm terminals (done by an electrician, not me). The light on the bridge constantly flashes once every 5 seconds no matter what I do. I have held the button for long over 15 seconds (up to 30 seconds), held it for 5 seconds, powered off the boiler and back on but the light does not flash any faster or change at all.
I removed the cover off the bridge and checked the voltage on the cables coming from the boiler and am getting 27v.
At this stage I'm not sure what else to do to try get it to bind. Any help would be much appreciated.

P.s. the HR92 valves binded just fine

Its flashing what exactly though? I assume it is a red LED? Is it a 0.5 second on & 0.5 second off, or is it 0.5 seconds off and 0.1 second on or is it 3 consecutive flashes in a row?

Have you spoken to Vokera directly? I have just had a conversation with a friend who works at Vokera and he believes you need an adaptor for this to work (Vokera part number 29450143). I would 100% check with Vokera technical first on 0844 391 0999.

Yes its the red LED. Its a quick flash on so feels more like 0.1 seconds on but then its off for 4.5 seconds. Keeps repeating this cycle no matter what I do by pressing and holding the button or powering it off and on again. I have not spoken to Vokera yet but I'm assuming once I have power going to the R8810 box I should be able to bind it to the controller? I have checked and there is 27V coming in on the wires from the boiler.
The literature with the boiler says it is OpenTherm enabled.

It does seem strange, but I am not 100% sure the effects on the OpenTherm Bridge if it goes directly to a fault condition.

Have you spoken to Resideo technical support (the manufacturer of Honeywell Home products) to see if the device is faulty? They are available on 0300 1301299 and make sure you get a Case Reference Number, should you need to return the item.

I have contacted them via email and the only help they could give me was the procedure for binding the devices. After that they said I have to get a Honeywell installer to call out, problem is I can't find any in Dublin.
I have been ringing the Resideo Tech number all day but can't get through to the Installers helpline. I will try Vokera to ensure it is all wired up correctly on the boiler side (Although I'm pretty sure it is) and keep trying Resideo to see if they can help.
After that I don't know where to go only to assume the box is faulty and look for a replacement.

I think I had the led flashing like that when there was a problem on the opentherm connection to the boiler. i.e. it has supply voltage but no communication is established with the boiler.

I looked a bit on internet and found some info that is worth checking with a professional. Note: I'm am not a professional installer, don't follow these instructions blindly, I don't want to cause any trouble

This pdf: https://www.britishgas.co.uk/british-ga ... A216B5.PDF shows a simple on-off thermostat connection. It just happens to deliver a voltage that powers the OT bridge but it is not an OT connection, explaining the red led blinking behavior.

Further, in this instruction film https://www.youtube.com/watch?v=2C6iDhF-gNc at 1:45 they talk about moving wires from CN5 to CN6 i.o. to obtain an OT connection on a vokera boiler, at timestamp 2:00 you can see opentherm written next to the 2 left pins of CN6.
CN6may correspond to CN6 as on page 32 in the before mentioned PDF https://www.britishgas.co.uk/british-ga ... A216B5.PDF

If CN6 has no connector, than you need to buy one as mentioned by The Evohome Shop.

Thanks Bart, I did eventually come across this info. Turns out the wiring instructions i got from Vokera were the low voltage on/off switching terminals and not the opentherm terminals.
I had to purchase the PCB connector you mentioned and wire up the opentherm bridge to CN6 on the two left hand connections. Once I done that I was able to bind the bridge to the controller and the heating side of the boiler worked fine.

Problem now is with the DHW side. Since i wired up the opentherm controls the DHW has stopped functioning correctly (Its a combi boiler). Now when i turn on the hot tap I get hot water for about 30 seconds and then it goes to room temperature. Turns out with this Vokera boiler once the boiler detects the opentherm connection it disables the front panel controls and takes all of its settings from the opentherm controller. This is ok if you have the Vokera opentherm controller as it lets you set the CH temperature and the DHW temperature setpoints but the evohome controller only lets you setup the Ch channel.
I have been onto Vokera and they have told me that there is no way around this. So I think I have to change the opentherm bridge out for the BDR91 relay box unless anyone knows a way around this problem.

Bit of a shame as I wanted to get the opentherm working on it.

It might be worth to investigate if adding an opentherm gateway ( http://otgw.tclcode.com/ ) solves this problem.
Setting it up requires some technical skills, and if it will work for your setup remains to be seen, it may also require integration in a home automation system, adding complexity.

Also, in this thread https://www.automatedhome.co.uk/vbullet ... connection a possible solution is mentioned that does not require permanent extra hardware.