21
Instruction for Use | HCA 56x and 8x8
Single sensor device with start sensor Double sensor
For heating systems with tmmin≥55°C For heating systems with tmmin≥35°C
The heat cost allocator calculates with a set
reference temperature of 20 °C
The heat cost allocator calculates with a variable
reference temperature TAir temperature.
Application:
Single sensor devices with start sensor are used in
areas where normal ambient temperatures are given.
For low temperature heating systems the double
sensor device is recommended.
Application:
Double sensor devices are used in areas where
precise measuring of the ambient temperature
is necessary and/or in low temperature heating
systems.
For radiators which are covered or blocked by
fixtures, normally the single sensor devices are used
because the double sensor device is not in a position
to capture the current ambient temperature due to
the heat accumulation.
Radiators which are covered or blocked by fixtures
are detected automatically by the double sensor
system which then switches over internally to the
single sensor mode.
5.4 Comparison of the Measuring Principles
Within one billing unit, only one measuring principle (either single sensor measuring
principle with start sensor or double sensor measuring principle) can be used. Mixed
fitments or the use of different types of devices in the same billing unit is therefore
also not allowed.
The processes for determining the K-value for the single sensor device with start
sensor and the double sensor device are identical. It is only the measuring principle
that is different.
5.5 Temperature Measurement and Calculation
The temperature is measured with an NTC – resistor. For the resistance measurement the dis-
charging time of the capacitor is measured. The measurement is carried out as follows:
5.5.1 Measuring of a Resistor, Principle
1. Charging of the capacitor
2. Discharging of the capacitor through the resistance which is to be measured.
At the same time a 16+1 bit-timer starts with the
discharge to measure the discharging time
3. As soon as the voltage on the capacitor terminals reaches a certain value, an
interrupt is induced and the timer stops. At the same time the discharging of
the capacitor is stopped as well.
After the three mentioned stages, the timer provides a 16-bit-value which corresponds to the
discharging time of the capacitor through the resistance which is to be measured. In case the
resistance is known (reference resistance), the constant ratio between discharging time and
resistance can be assessed.
5.3.1 Heat Accumulation Mode
In order to avoid faulty measuring due to heat accumulation (e.g. in case the radiator is hidden
by panels), the device switches from a defined ambient temperature (e.g. 28°C) to the one sen-
sor mode and calculates with an ambient temperature of 20° C.
To Next Page
Loading...
Need help?
General
