Calibration Menu / 7.5 - IDU Heating Temperatures
For controlling the power output of the outdoor unit, two communication methods can be selected between MiniHPC and the outdoor unit. The first method is labeled as . In this case, MiniHPC simulates a connected standard indoor unit, and power regulation is based on the calculation of the internal PID controller and processes that are permanently built into the outdoor unit.
The second method, labeled as , allows MiniHPC to directly send requests to the outdoor unit to set the exact compressor frequency, using the PID controller built into MiniHPC for the calculation. This regulation method is, in most cases, more precise than IDU sim, preventing unwanted oscillations and compressor cycling.
The second method, labeled as , allows MiniHPC to directly send requests to the outdoor unit to set the exact compressor frequency, using the PID controller built into MiniHPC for the calculation. This regulation method is, in most cases, more precise than IDU sim, preventing unwanted oscillations and compressor cycling.
IDU sim
To be able to configure this part of the menu, it is first necessary to understand how the air conditioner regulates its output based on the set temperature (Tpreset) and the room temperature (Tamb).
MiniHPC operates by simulating a connected standard indoor unit. It sends the outdoor unit data about the set temperature and the measured room temperature (in addition to other parameters such as the liquid refrigerant temperature, mode, fan speed, silent mode, etc.).
The outdoor unit then decides, based on these parameters, whether to turn the heating on or off and, if it is already on, whether to reduce or increase the output.
The outdoor unit does not attempt to regulate heating precisely at the set temperature but uses a positive offset from the set temperature. This is typically 3–3.5°C for most models. For example, if a standard air conditioner is set to a heating temperature of 25°C, it actually tries to maintain a room temperature of approximately 28°C. Once this heating temperature is reached, the unit begins to modulate its output so that the temperature does not unnecessarily drop or rise.
If the room temperature reaches a value 5°C higher than the , the outdoor unit will turn off the heating and wait until the temperature drops to a level equal to the plus 2°C.
MiniHPC does not modify the for regulation; it is fixed and unchangeable, and its value can be adjusted in this part of the menu.
The only parameter that MiniHPC manipulates is the room temperature (Tamb), by sending the outdoor unit a Tamb value calculated using the formula:
The only parameter that MiniHPC manipulates is the room temperature (Tamb), by sending the outdoor unit a Tamb value calculated using the formula:
[Tamb] = [Preset Temperature] + [Temperature Offset] + ([Measured Temperature] - [Set Temperature])
In this way, the outdoor unit can regulate the heating to higher temperatures—up to the standard values available with a classic indoor unit setup (30°C).
The values for the and define the range of temperatures that MiniHPC will send to the outdoor unit as Tamb.
sets the maximum temperature that will be sent to the outdoor unit as Tamb according to the formula + + .
If the difference between the actually measured temperature and the set temperature is greater than this limit, the outdoor unit will receive the value of this limit. (After exceeding this limit by 3.5°C, this function is disabled and the outdoor unit receives the real values as a prevention against overheating. At that moment, the outdoor unit turns off the heating.)
Temperatures higher than 2°C in this setting do not make sense because if the temperature exceeds the limit by more than 2°C, the outdoor unit will turn off the heating anyway. By default, this limit is set to 3°C, meaning that the behavior is as if this limit were not applied, since the outdoor unit turns off the heating before the limit would come into effect.
The setting is useful when the outdoor unit begins to cycle during the compressor startup. In reality, especially during transitional seasons, when the compressor is turned on, it typically runs at about 50% capacity and then, after a few minutes, modulates its output either up or down. However, in some cases, that 50% may be too much, causing the heating water temperature to rise quickly, which results in the temperature threshold being exceeded and the compressor turning off. After the temperature drops for a few minutes, it turns on again, and so on.
Thanks to this function, if the switching temperature is exceeded, a slightly lower temperature is sent to the outdoor unit so that it believes it has not exceeded the threshold. At the same time, that temperature will be high enough to force the outdoor unit to modulate its output lower, thus regulating the output within the proper range without cycling.
If the difference between the actually measured temperature and the set temperature is greater than this limit, the outdoor unit will receive the value of this limit. (After exceeding this limit by 3.5°C, this function is disabled and the outdoor unit receives the real values as a prevention against overheating. At that moment, the outdoor unit turns off the heating.)
Temperatures higher than 2°C in this setting do not make sense because if the temperature exceeds the limit by more than 2°C, the outdoor unit will turn off the heating anyway. By default, this limit is set to 3°C, meaning that the behavior is as if this limit were not applied, since the outdoor unit turns off the heating before the limit would come into effect.
The setting is useful when the outdoor unit begins to cycle during the compressor startup. In reality, especially during transitional seasons, when the compressor is turned on, it typically runs at about 50% capacity and then, after a few minutes, modulates its output either up or down. However, in some cases, that 50% may be too much, causing the heating water temperature to rise quickly, which results in the temperature threshold being exceeded and the compressor turning off. After the temperature drops for a few minutes, it turns on again, and so on.
Thanks to this function, if the switching temperature is exceeded, a slightly lower temperature is sent to the outdoor unit so that it believes it has not exceeded the threshold. At the same time, that temperature will be high enough to force the outdoor unit to modulate its output lower, thus regulating the output within the proper range without cycling.
The actual behavior with the given temperature settings must be monitored during operation, as temperature regulation behaves differently among different air conditioner models, and what works on one model may not work on another.
is a factor that adjusts the Tamb value sent to the outdoor unit according to the following formula:
[Tamb] = [Preset Temperature] + [Offset Temperature] + ([Measured Temperature] - [Set Temperature]) * [Temperature Gain]
From the formula it is clear that a value of 1.0 has no effect on the calculation. Values higher than 1.0 will cause the difference between the measured and set temperatures to be amplified, while values lower than 1.0 will dampen this difference.
The calculated values Tamb and Tpreset, which MiniHPC sends to the outdoor unit, can be monitored in the menu 4.1 Outdoor unit under .
PID
When selecting the PID controller option, it is possible to limit the compressor frequency range, set the upper temperature limit, and adjust individual PID controller components.
- lower limit of compressor frequency
- upper limit of compressor frequency
- temperature threshold at which the compressor is turned off. For example, if the upper limit is set to +3°C and the output water temperature is 30°C, the compressor will shut down when the temperature exceeds 33°C.
This situation may occur when the heating water reaches the set temperature, the PID controller gradually reduces the compressor frequency to the Minimum Frequency limit, and if the heating output at this frequency still exceeds the required heat to maintain the set temperature, the output heat exchanger temperature will continue to rise until it reaches the Up Temperature Limit.
This situation may occur when the heating water reaches the set temperature, the PID controller gradually reduces the compressor frequency to the Minimum Frequency limit, and if the heating output at this frequency still exceeds the required heat to maintain the set temperature, the output heat exchanger temperature will continue to rise until it reaches the Up Temperature Limit.
- individual PID controller components. Their significance can be found, for example, on Wikipedia
For temperature control based on inlet water temperature T2, the default values are: P:50, I:12, D:10
For control based on outlet water temperature T3, the default preset values are: P:15, I:30, D:0
These values should be adjusted according to the actual behavior of the PID controller in the specific heating system.
For control based on outlet water temperature T3, the default preset values are: P:15, I:30, D:0
These values should be adjusted according to the actual behavior of the PID controller in the specific heating system.
If the is set below 30Hz, MiniHPC will periodically increase the compressor frequency every 38 minutes for better oil distribution in the refrigeration circuit.