How you recognise it
The temperature and humidity sensor of a TapHome smart switch (PBT, PBM) or controller with display (MZC, SZC, TC) shows values that do not match the room:
- Humidity is higher than a hygrometer in the room shows
- Temperature is lower than a thermometer in the room shows, often by 1 to 2.5 °C
- In a cold room, such as a garage or a cellar, humidity climbs above 100 %
- A thermostat that takes its temperature from the switch heats more than needed
- After a power outage the values keep changing for about half an hour
Cause
The electronics of the switch warm it slightly. The firmware of the switch subtracts an estimate of this self-heating from the measured temperature, and the Temperature compensation setting in the service settings of the module decides how much. When the setting is stronger than the real self-heating (typically Medium), the temperature reads too low. The switch then recalculates the relative humidity for that lower temperature, so the humidity reads too high. With older firmware of the switch a cold room can even show more than 100 %.
Solution
Step 1: Update the firmware of the switch and controller modules
Service installation partner
In the appSettings → Software updates
Open Settings → Software updates and update all switch and controller modules to the latest firmware offered. Do this first: in a cold room with older firmware the reading stayed above 100 % even after a weaker compensation.
Step 2: Set the temperature compensation to Low
Service installation partner
In the appSettings → Hardware
Open Settings → Hardware, open the switch or controller module and in its service settings set Temperature compensation to Low. Do it on every module whose temperature or humidity does not match the room.
The change applies without restarting the module. The switch adjusts its estimate gradually, so the values settle within about 30 minutes. The same happens after every power outage, when the estimate starts again from zero.
Step 3: Compare with a reference thermometer
Admin home owner
- Wait about 30 minutes after the change
- Place a thermometer with a hygrometer next to the switch, not on it, and leave it there for 15 to 20 minutes
- Compare both the temperature and the humidity with the values in TapHome
Step 4: Correct a remaining constant difference with calibration
Service installation partner
If measurements at different times of the day show the same difference, set Temperature calibration and Humidity calibration in the service settings of the temperature and humidity sensor of the switch.
Temperature calibration only shifts the temperature, it does not recalculate the humidity. Set both values separately, and only when the difference is the same in several measurements.
If it still does not work
- Off switches the estimate off; the switch then reads somewhat higher than the room. Use it only when Low still reads too low against the reference thermometer
- If a cold room still shows more than 100 % after the firmware update and the change to Low, contact TapHome support