How does the external temperature sensor function work?

03 Aug 2023

This article will give you a more detailed description of how this function works and behaves when a temperature is set.

 

APPLICABLE PRODUCTS

All Products that support the external temperature sensor function.

 

PRE-REQUISITES

Intesis AC Interface

External Temperature Sensor

 

IN THIS ARTICLE 

For the sake of simplicity, KNX is used as a reference in this article. However, this is also applicable to the Modbus variant.

 

The base of the function is the following calculation.

“AC Setp. Temp.” = “Ambient ref. Temp.” - (“KNX Amb. Temp.” - “KNX Setp Temp.”)

  • AC Setp. Temp.:            AC indoor unit setpoint temperature (Temp. set on the AC)
  • Ambient Ref. Temp.:     AC indoor unit return temperature (Temp. measured by the AC)
  • KNX Amb. Temp.:        Ambient temperature provided from KNX (Temp. measured by KNX)
  • KNX Setp. Temp:         Setpoint temperature provided from KNX (Temp. set from KNX)

 

As an example, consider the following situation:

User wants:                                       19ºC (KNX Setp. Temp.)
User sensor (a KNX sensor) reads:    21ºC (KNX Amb Temp.)
Ambient temp. read by the AC is:     24ºC (Ambient Ref. Temp)

 

In this example, the final setpoint temperature that the Gateway will send out to the indoor unit (“Setp.
Temp.”) will become 22ºC = 24ºC – (21ºC - 19ºC). This is the setpoint that will be sent to the AC unit.

This formula will be applied as soon as the Control_ Setpoint Temperature and Control_ Ambient
Temperature objects are written at least once from the KNX installation. After that, they are kept always
consistent.

Note: This formula will always drive the AC indoor unit demand in the right direction, regardless of
the operation mode (Heat, Cool, or Auto).


Detailed Example:

On the following page, you can see a diagram that shows the behavior of the target temperature of the
AC unit in relation to certain time-based (time 1,2,3,...) temperature values.


As described above the User wants a Temperature of 19°C in his Room. The KNX Sensor Measures 21°C
and the AC Measures 24°C

 

Time 1: Start (AC Setp. Temp 22°C)
Time 2: AC Amb. Temp. decrease to 23 °C (AC Setp. Temp. decrease to 21°C)
Time 3: AC Amb. Temp. decrease to 22 °C (AC Setp. Temp. decrease to20°C)
--
Time 6: KNX Amb. Temp. decrease to 20 °C (AC Setp. Temp. increase to 19°C)
--
Time 8: Temp. reached (unstable)
Time 9: KNX Amp. Temp. below 19 °C (AC Setp. Temp. increase to 20°C)
Time 10: Temp. reached (unstable)
Time 11: Temp. reached (stable)