MLR003R Ambient and Flow Temperature Estimation

Every MLR003 device contains a “Thermoelectric Generator (TEG)” element, which generates electrical energy when there is a temperature difference.
The TEG harvests energy from the temperature difference between the heating flow temperature and the ambient temperature (usually room temperature).
The MLR003 comes with an aluminium housing as a functional part to generate electrical energy.
The actuator has a valve-side temperature sensor to determine the flow pipe temperature and an ambient sensor to determine the temperature away from the flow pipe. Because the ambient sensor is surrounded by the aluminium housing and is still very close to the radiator, when the radiator is heating, the value measured by the ambient sensor is higher than the actual room temperature. Thus an algorithm is applied to estimate the room temperature.
A controllable offset for the flow sensor is available to compensate for devices which are mounted above exposed hot water pipes. It can be set by sending an FPORT 0x08 Downlink.
Valve adapters further increasing the offset between the internal flow sensor and the water temperature must be taken into account

Fluid (water) temperature FSRV

Recommended offset for the flow sensor value FTMP applied in FPORT 0x08

(Offset values derived in climate chamber and without valve adapter)

55°C

10°C

65°C

13°C

70°C

14°C

To obtain an estimate of the ambient temperature, the device measures the flow temperature every 5 minutes and performs a moving average across the last 30 minutes. It then performs the following computation

Byte	Uplink in FPORT #1	Details	Description
2	FSRV	Flow Sensor Raw Value	The uncompensated flow temperature measured at the valve side
3	FTMP	Flow Temperature Value	The flow moving average, with offset applied Moving Average of Flow Sensor Raw Value + OFFSET (set via FPORT 0x08) Default OFFSET = 0
4	ASRV	Ambient Sensor Raw Value	The uncompensated ambient sensor value
5	ATMP	Ambient Temperature Value	Ambient Temperature calculated from

The Set Point Value “SPV“ is set by the user through Downlink on FPORT 0x01
The MLR003R uses either the ambient temperature coming from an external sensor (“RT“ in FPORT 0x01 Downlink) or the internal Ambient Temperature (“ATMP“) estimate

FPORT 0x01 Downlink Byte 2 Room Temperature (RT) value	Temperature Value
0	Use internal Ambient Temperature (ATMP) estimate
Room Temperature from external sensor	Use the room temperature value from the external sensor

In order to achieve a Set Point Value (SPV) Ambient Temperature, the device applies a PID control algorithm.