Ecotec 618 Nest Opentherm VR33 VR65/66

[tinkerday]

I have an Ecotec 618 boiler. I am working to get a Nest thermostat modulating the boiler via Opentherm (easier said than done!)

I have connected via VR33 Opentherm bridge which seems to be communicating ok (no error on nest and D.90 reading 1 on boiler).

Problem I have is that there doesn’t appear to be any modulation of the boiler flow Setpoint and also the DHW won’t work now!

From reading around the subject I believe that I may need to install a VR65 as well for the boiler to “see” the dhw tank via ebus.

VR65 seems to be discontinued and is replaced by a VR66.

Does anyone know if this is interchangeable or have any other tips that may help me on the journey!?

I think that VR66 just needs to be configured for single zone operation 🤞🏻

thanks in advance….

[bruce_miranda]

How was the CH and HW triggered before you added Nest and the VR33?

[tinkerday]

Standard S Plan

[bruce_miranda]

So did you get the Nest working with HW?

In a normal non Vaillant S plan, you have 2 zone valves. The 2 channel timer opens the CH and/or HW. The zone valves in turn fire the boiler.

Normally, a Vaillant will work as a Heat only CH boiler unless you use the eBus controls. Which is why that second HW knob is normally useless.

I have absolutely no idea what Nest and or Vaillant have implemented for HW via OT/VR33. I know the Evohome doesn't issue a HW specific command to the boiler. So the Vaillant just works as a normal Heat only boiler even via VR33 and Evohome.

BUT there is a way you can trick the boiler into HW mode, which involves using a VR65/VR66. You can find that using my other thread.

I do not understand how Nest HW via OT is meant to work? Can you explain?

The Vaillant boiler doesn't understand anything besides eBUS..So the VR65 is the only way the boiler is able to get a HW temperature reading, or put itself into HW. While Nest could put the boiler into HW mode, I don't know how the Vaillant or the Nest is ever going to know the temperature of the HW.

[Beneathome]

I’m trying to do something similar, but with a Vaillant vr61 controller attached to a ecotec plus 630.
bruce_miranda, do you know if there’s a similar trick to getting the VR33 working with this combination?

[bruce_miranda]

A VR61 is for 2 x CH zones. So I am not sure how or if the boiler will ever go into HW mode with that.
The boiler only works at CH mode without the Vaillant controls.

The boiler seems to need an eBus command to switch between HW and CH modes. That eBus command is sent via the VR65. Infact when the VR65 is connected the boiler works in HW priority mode until the demand for HW is satisfied and then it flips back to CH mode.

[Beneathome]

Thanks for the quick response, and thank you for sharing your expertise in this.

I’ve currently got a 2-zone CH + HW system and I’m looking to add an additional zone which will be UFH.
Ideally, I’m looking for a way to incrementally update the controls, with a longer term goal of moving to an OpenTherm system, which doesn’t tie me to Vaillant (the boiler will probably need replacing within 5 years).
Any advice here is greatly appreciated!

[bruce_miranda]

Vaillant doesn't understand anything besides eBus. Even the VR33 is just a gateway between OT and eBUS, to satisfy some Dutch requirements.

I have absolutely no idea how many OT commands are recognised and translated to equivalent eBus commands by the VR33.

A Vaillant boiler without the Vaillant controls only works as a single Heat Only boiler. So it never enters the HW mode. This is why you have to choose a flow temp that heats your HW and then use that same setting for your CH.

It's only when used in conjunction with a Vaillant wiring centre e.g. VR65 does the HW mode become operational and even then you need things like a sensor to get the HW knob on the boiler to really work.

The moment you have multiple CH, UFH and HW zones, you are starting to push the boundaries of what is capable using normal controls. In theory the heat demands are UFH < CH < HW. You need to start thinking about smart(er) controls.