Does the BTH-RM need a Bosch Smart Home Controller?

No. It is a Zigbee 3.0 device and joins the Gateway’s Zigbee network with its install code. Edge then reads it and writes its settings directly.

Can it control Bosch radiator thermostats through Edge?

Not by itself. In a Bosch system the Bosch controller links them. On the Gateway they are separate devices, so an Edge automation can write the room thermostat’s temperature to each BTH-RA’s remote temperature, refreshing it at least every 30 minutes.

Can it switch underfloor heating actuators?

No. Bosch says the battery Room Thermostat II is not designed to drive underfloor heating controls in the distribution cabinet. The Room Thermostat II 230 V connects to the actuators directly.

What probe does the sensor input take?

A 10 kΩ NTC temperature sensor. Bosch sells a sensor cable of that type, and the probe can be used as a floor sensor or to measure elsewhere in the room.

How do I reset it to factory settings?

Remove one battery and refit it while holding the knob. Keep holding until the LED flashes orange and RES appears, release briefly, then hold again until the LED lights green. The thermostat restarts.

Bosch BTH-RM Zigbee room thermostat

Compatibility

Compatible with EpiSensor Edge over Zigbee.

Pair it with the Zigbee radio on an EpiSensor Gateway. Edge reads it locally on the Gateway.

Edge reads 23 values from it, listed under Interface.

Connect it with

Gateway ZGW-20
From €899 ex VAT Configure Gateway

Specifications

The BTH-RM is the battery version of Bosch’s Room Thermostat II. It sits on the wall at a representative point in the room, shows the actual and set temperature and the room humidity on an LED display, and runs on four AAA alkaline cells that Bosch rates for a typical life of under two years. It mounts on a wall plate or stands on a bracket on a flat surface.¹

Power: Battery. Four 1.5 V AAA (LR3) alkaline cells. Bosch quotes a typical life of under two years.¹
Type: BTH-RM¹
Radio: Zigbee 3.0, 2.4 to 2.4835 GHz¹
Maximum transmit power: 10 dBm¹
Range in the open: Under 100 m¹
Setpoints: Heating and cooling, 5 to 30 °C each³
Calibration offset: -5 to +5 °C³
External sensor input: NTC 10 kΩ probe, for example a floor sensor²
Display: LED: actual and set temperature, humidity, operating mode¹
Ambient temperature: 0 to 50 °C¹
Humidity: Up to 80 %, non-condensing¹
Dimensions (W × H × D): 86 × 87 × 28 mm¹
Weight: 85 g without batteries¹

Where it is used

Room temperature and humidity in offices, meeting rooms and small clinics, measured on the wall where people are rather than at the radiator.
Indoor environmental monitoring
A reference temperature for the Radiator Thermostat II heads in the same room, with Edge passing the room reading to each valve.
HVAC energy monitoring for commercial buildings
Floor surface temperature beside air temperature in rooms with underfloor heating, using a 10 kΩ NTC probe on the sensor input.

Interface

Readings and settings, with units and ranges where Bosch publishes them. readable, readable and writable.

Download

Reading	Unit	Range or values	Access
Measurements 8
Climate	-	-	Read only
Local temperature	°C	-	Read only
Running state	-	`idleheatcool`	Read only
Control sequence of operation	-	`cooling_onlyheating_only`	Read only
Setpoint change source	-	`manualscheduleexternally`	Read only
Humidity	%	-	Read only
Cable sensor temperature	°C	-	Read only
Error state	-	-	Read only
Controls 3
Occupied heating setpoint	°C	5 to 30 °C	Read and write
Occupied cooling setpoint	°C	5 to 30 °C	Read and write
System mode	-	`offheatcool`	Read and write
Settings 9
Operating mode	-	`schedulemanualpause`	Read and write
Local temperature calibration	°C	-5 to 5 °C	Read and write
Cable sensor mode	-	`not_usedcable_sensor_without_regulationcable_sensor_with_regulation`	Read and write
Window detection	-	Binary state	Read and write
Boost heating	-	Binary state	Read and write
Child lock	-	Binary state	Read and write
Display brightness	%	0 to 100 %	Read and write
Display switch on duration	s	5 to 30 s	Read and write
Activity LED	-	`offautoon`	Read and write
Diagnostics 3
Battery	%	0 to 100 %	Read only
Voltage	mV	-	Read only
Battery low	-	Binary state	Read only

cable_sensor_mode selects what the probe input does: not_used, cable_sensor_without_regulation (report only) or cable_sensor_with_regulation. The probe reading is cable_sensor_temperature.³

Bosch’s error E04 is a fault on the external sensor input. With no probe fitted, set cable_sensor_mode to not_used to clear it.^2, 3

Zigbee2MQTT records excessive battery drain on firmware 0.2.9, so check the firmware version on sites where cells run down early.³

Setup

Have the install code ready
The thermostat joins with a Zigbee install code, held in the QR code on the battery cover. The Gateway’s Zigbee network needs that code before it will accept the thermostat.³
Open pairing in Edge
Open pairing on the Gateway’s Zigbee network in Edge, then power the thermostat up by inserting the batteries. The status LED flashes orange while pairing is active.¹
Confirm the join
The LED flashes green when pairing has succeeded and red once if it has failed. After a failure, reset the thermostat to factory settings and try again.¹
Mount it
Fix the mounting plate to the wall away from cables and pipes, or use the bracket to stand it on a flat surface. Choose a spot that represents the room, away from radiators and direct sun.¹
Check one reading
Confirm that Edge identifies it as Bosch BTH-RM. Compare the room temperature and humidity with a reference instrument beside it, and set the calibration offset if they differ.

Common questions

Does the BTH-RM need a Bosch Smart Home Controller?: No. It is a Zigbee 3.0 device and joins the Gateway’s Zigbee network with its install code. Edge then reads it and writes its settings directly.^1, 3
Can it control Bosch radiator thermostats through Edge?: Not by itself. In a Bosch system the Bosch controller links them. On the Gateway they are separate devices, so an Edge automation can write the room thermostat’s temperature to each BTH-RA’s remote temperature, refreshing it at least every 30 minutes.^2, 3
Can it switch underfloor heating actuators?: No. Bosch says the battery Room Thermostat II is not designed to drive underfloor heating controls in the distribution cabinet. The Room Thermostat II 230 V connects to the actuators directly.²
What probe does the sensor input take?: A 10 kΩ NTC temperature sensor. Bosch sells a sensor cable of that type, and the probe can be used as a floor sensor or to measure elsewhere in the room.²
How do I reset it to factory settings?: Remove one battery and refit it while holding the knob. Keep holding until the LED flashes orange and RES appears, release briefly, then hold again until the LED lights green. The thermostat restarts.¹

Related devices

Sources

Room thermostat II quick instructions (BTH-RM) (opens in a new tab) (PDF) Bosch Smart Home
Room thermostat II help (opens in a new tab) Bosch Smart Home
Bosch BTH-RM device documentation (opens in a new tab) Zigbee2MQTT
Bosch BTH-RM Zigbee definition (opens in a new tab) zigbee-herdsman-converters · v26.111.0

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