Bosch EasyControl on a Vaillant boiler: only with an adapter and VR 33, otherwise on/off

Short answer: it is possible, but it is cumbersome. Vaillant boilers (ecoTEC plus, ecoTEC pro, older condensing models) use the eBusprotocol, not OpenTherm. The Bosch EasyControl only works with modulation if the boiler has a Vaillant VR 33 OpenTherm module, with the EasyControl Adapter connected behind it. Without a VR 33 you can only connect the adapter to the on/off contact: remote control then works, but the boiler does not modulate. For a Vaillant, an eBus thermostat from Vaillant itself is usually the simpler choice.

Vaillant by series

Vaillant series	Thermostat connection	EasyControl modulating	EasyControl on/off	Spare parts
ecoTEC plus	eBus (OpenTherm with VR 33)	With VR 33 + adapter	With adapter on the on/off contact	ecoTEC plus parts
ecoTEC pro	eBus (OpenTherm with VR 33)	With VR 33 + adapter	With adapter on the on/off contact	ecoTEC pro parts
Older condensing models (HR Solide, Thermo-/Turboblock)	On/off or eBus; see the manual	Usually not	With adapter	Vaillant spare parts

Vaillant fault codes with cause and part: Vaillant fault codes.

What you need

Modulating: the VR 33 module (Vaillant, available separately), the EasyControl Adapter and the thermostat. On/off only: the thermostat and the adapter. Note that a VR 33 without a connected OpenTherm thermostat can block the eBus control; so only fit the module once you are actually going to use it.

Step by step: connecting EasyControl

Always read your boiler's installation manual first. If you are unsure about the terminals, have an installer do it.

1. Disconnect the boiler from the power (unplug it) and disconnect the existing thermostat. Bosch specifies that only one thermostat may be connected to the boiler.
2. Connect the EasyControl Adapter with two wires to the boiler's thermostat terminals (on a Vaillant, the OpenTherm terminals of the VR 33; on on/off boilers, the on/off contact). The adapter needs its own power socket.
3. Connect the EasyControl thermostat with two wires to the adapter (no polarity).
4. Order when switching on: first the thermostat, then plug the adapter into the socket, then the boiler. The adapter searches for OpenTherm for about a minute; if it does not find it, it switches to on/off. To make it search again: unplug the adapter for 25 seconds.
5. Switch the boiler on, connect to your 2.4 GHz Wi-Fi via the Bosch EasyControl app (5 GHz does not work) and follow the setup.
6. After half an hour, check whether the boiler modulates (the flame keeps burning at lower output) and whether the app shows the boiler status.

Things to bear in mind

• On/off via the adapter: the boiler does not modulate and the app reads nothing (no water pressure, no consumption). You do keep remote control, the time programme and presence detection.
• OpenTherm via the adapter: modulating. The water pressure is only shown if the boiler has a pressure sensor and the values have been checked once.
• Nefit Easy Connect or RCC module on an older boiler: remove it first, EasyControl does not work together with it.
• One EasyControl per boiler. You control multiple rooms with the Smart Radiator Thermostats (radiator heads), not with a second thermostat.
• 2.4 GHz Wi-Fi is required; a network that only broadcasts 5 GHz does not work.

Frequently asked questions

Does the EasyControl work directly on a Vaillant ecoTEC?

No. The ecoTEC uses eBus and the EasyControl uses EMS bus. Without a VR 33 and adapter, only on/off is possible.

What is the VR 33?

An OpenTherm interface module from Vaillant for the Dutch market. It sits in the boiler and provides OpenTherm terminals, so that an OpenTherm control (here: the EasyControl via the adapter) can control the boiler with modulation.

Is it worth it?

Only if you specifically want the Bosch app and radiator heads. For remote control of a Vaillant, an eBus thermostat from Vaillant is cheaper and needs no extra modules.

Can I see the water pressure in the app?

Via the VR 33 and adapter, only if the boiler has a pressure sensor and the value has been checked once. Never with on/off.

Other brands

• Overview of all brands: does EasyControl fit my boiler?
• EasyControl on a Nefit or Bosch boiler
• EasyControl on an Intergas boiler
• EasyControl on a Remeha boiler
• EasyControl on an ATAG boiler

Sources: Bosch brochure "Is EasyControl geschikt voor mijn verwarmingssysteem?" (document number 6721867369, October 2024) and the page about the EasyControl Adapter on nefit-bosch.nl. Protocols of other brands: manufacturers' installation manuals. Page updated: 12 October 2026.