Worcester Bosch and OpenTherm

Worcester Bosch OpenTherm has eluded us here at MyBoiler.com for a while. New information has surfaced showing that it is indeed possible to use OpenTherm with a range of Worcester Bosch boilers using an adaptor. The boilers that operate using the modern EMS protocol system can be used with this adaptor to allow OpenTherm Thermostats to control Worcester Bosch boilers and other EMS protocol based boilers, although in the UK only Worcester Bosch is known to use some form of EMS.

If you have arrived directly at this page, you are able to see our main page on OpenTherm Capable Boilers and Controls.

Nefit EMS-OT OpenTherm Converter

Description: This adaptor will take an OpenTherm capable thermostat and translate to the proprietery Worcester Bosch bus interface. It translates from OpenTherm to EMS.

Where to buy:

https://wifithermostaten.nl/nefit-opentherm-converter.html

Nefit Moduline Easy Connect Adapter for OpenTherm Devices

Description: This adaptor allows the Worcester Wave or Nefit equivalent to connect to an OpenTherm interface. CV-Ketel is dutch for Boiler. This adaptor has now been superceded by the Nefit EasyControl adapter shown below.

Bosch / Nefit EasyControl Adapter for On-Off, OpenTherm and iRT

Description: This adaptor allows a Nefit or Worcester Wave thermostat to communicate to other boilers with On-Off, OpenTherm and iRT interfaces. Please note this adaptor only takes an EMS signal and outputs to On-Off, OT (OpenTherm) and iRT, not the other way round. It is not capable of allowing an OpenTherm thermostat to work with an EMS based boiler such Worcester Bosch.

Functions and Features According to Opentherm.eu

• ID0:HB0: Master status: CH enable
• ID0:HB1: Master status: DHW enable
• ID0:LB0: Slave Status: Fault indication
• ID0:LB1: Slave Status: CH mode
• ID0:LB2: Slave Status: DHW mode
• ID0:LB3: Slave Status: Flame status
• ID0:LB6: Slave Status: Diagnostic/service indication
• ID1: Control Setpoint i.e. CH water temperature Setpoint (°C)
• ID3:HB0: Slave configuration: DHW present
• ID3:HB1: Slave configuration: Control type
• ID3:HB3: Slave configuration: DHW configuration
• ID3:LB: Slave MemberID Code
• ID5:HB0: Service request
• ID5:HB2: Low water pressure
• ID5:HB3: Gas/flame fault
• ID5:HB5: Water over-temperature
• ID15: Maximum boiler capacity (kW) / Minimum boiler modulation level(%)
• ID17: Relative Modulation Level (%)
• ID18: Water pressure in CH circuit (bar)
• ID19: Water flow rate in DHW circuit. (litres/minute)
• ID25: Boiler flow water temperature (°C)
• ID26: DHW temperature (°C)
• ID27: Outside temperature (°C)
• ID28: Return water temperature (°C)
• ID35: Boiler fan speed Setpoint and actual value
• ID36: Electrical current through burner flame [µA]
• ID48: DHW Setpoint upper & lower bounds for adjustment (°C)
• ID49: Max CH water Setpoint upper & lower bounds for adjustment (°C)
• ID56: DHW Setpoint (°C) (Remote parameter 1)
• ID57: Max CH water Setpoint (°C) (Remote parameters 2)
• ID115: OEM-specific diagnostic/service code
• ID116: Number of succesful starts burner
• ID119: Number of starts burner during DHW mode
• ID120: Number of hours that burner is in operation (i.e. flame on)
• ID123: Number of hours that burner is in operation during DHW mode