Offset is the number of degrees below the setpoint at which the heater shuts down. The differential is the range of degrees at which the heater will operate.
For example, at a setpoint of 26.6°C, when the offset is 1°C and the differential is 0.5°C, the heater will turn on at 25°C and run until the room temperature reaches 25.5°C (Figure 1). In some controllers, these settings are simplified into heater on and heater off temperatures.
Figure 1: Example of setting the heater and minimum ventilation
Stage 1, 100% settings
Stage 1, setting temperature range -1°C
Set value
Heater temperature offset -1°C
Stage 1 Minimal ventilation
Heating is turned off
Differential heater -0,5°C
Heating is turned off
Correct setting of the heater offset and differential is the key to achieving a stable room temperature and limiting energy consumption.
The most common problem on the farm is heaters that switch off too close to the setpoint temperature. In such cases, the room temperature rises even after the heater is switched off, because the heated air needs some time to circulate and the sensors to detect an increase in room temperature. If the heater is programmed to switch off too close to the setpoint value, the room temperature will rise above this value, causing the minimum ventilation fans to work harder to cool the room.
It is advisable to set the controller to switch the heater off when the temperature is 0.8-1°C below the desired room temperature and to set the heater to switch on when the temperature drops 0.5°C below the desired temperature. It should be understood that each farm is different, depending on the number and size of heaters in the room and the area of heated rooms. An effective way of fine-tuning the heater is to record the current settings and monitor the room temperature during the on and off cycles of the heaters. Ideally, after the heater is switched off, the room temperature should rise to a level slightly below the setpoint without exceeding it. If the room temperature rises above the setpoint temperature, increase the offset of the heater temperature so that it switches off below the setpoint temperature. Proper heater settings can reduce energy consumption per heater per day, resulting in significant energy savings.
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