1260: DHW Cylinder Temperature

The DHW sensor (CS92 Wireless Cylinder Thermostat) will spontaneously broadcast the latest temperature of the stored hot water via a 1260 packet:

053  I --- 07:045960 --:------ 07:045960 1260 003 000EA5

This will be the DHW temperature displayed in the Evohome controller's UI.

It is unclear when these packets are sent (it is certainly not periodic), but there is anecdotal evidence that they are sent more frequently as the DHW temperature nears the corresponding setpoint.

Other Verbs

The controller (not the sensor) will always respond to an RQ with what it believes to be the latest temperature:

095 RQ --- 18:013393 01:145038 --:------ 1260 001 00
045 RP --- 01:145038 18:013393 --:------ 1260 003 000F1D

The RQ payload must be 00.

Payload Structure

segment	size	contents
unused	[0:2]	always 00
temperature	[2:6]	current temperature (degrees C) / 100

If the segment is 7FFF, then the temperature is unknown.

Sample Code

Using Python, the payload can be decoded as:

def _temp(seqx) -> Optional[float]:
    return int(seqx, 16) / 100 if seqx != "7FFF" else None

def parser_1260(payload) -> dict:
    assert payload[:2] == "00"

    return {"temperature": _temp(payload[2:])}

Related Packets

• 0x10A0: DHW Cylinder Setpoint
• 0x1260: DHW Cylinder Temperature
• 0x1F41: DHW Operating Mode