On the surface, many people assume that an inverter system can achieve faster cooling/heating or achieve greater capacity if the indoor/outdoor combination ratio becomes 130% because they suppose that the frequency of the inverter system can be increased sharply. Let us consider the first assumption of faster cooling or heating. In actual operation, when you turn on 130% indoor units concurrently, the frequency of inverter system can only be increased very slowly. When the frequency of inverter systems is increased too quickly, the discharge gas temperature will become too high (e.g. 110 °C ) and this will cause the compressor to cut-off immediately; then, the inverter system has to increase its frequency from the bottom again. In a Copeland Scroll Digital system, the compressor capacity can be changed from 10% to 100% instantaneously, without any effect on the discharged gas temperature. So a Copeland Scroll Digital system can achieve faster cooling/heating compared to the inverter system. The second wrong impression is that an inverter system can provide more capacity, since it can increase the compressor motor speed. This is not actually the case. For example, in a 10HP rated inverted system, the rated compressor used is only 3.5HP+5.0HP. This means that the rated compressor capacity is less than the rated system capacity. So the compressor has to be run at a higher speed to get the rated system capacity. But when the temperature of the Inverter driven board exceeds its setting value (e.g. 84 °C ) or the discharge temperature of the compressor exceeds its setting value (e.g. 3.4Mpa), then the inverter system will get into a “Frequency Limit” operation stage, which not only cannot meet the 130% capacity request, but also gives lower capacity output than the rated one. By contrast, a similar 10HP Copeland Scroll Digital system will have a 6HP+5HP compressor capacity. This ensures that the Copeland Scroll Digital system is able to provide higher capacity when the cooling/heating demand goes up.
The defrost control is initiated when three conditions are met: 1). The system has run in heating mode for at least 50 minutes 2). The ambient temperature is above –5 °C 3). The condenser mid coil temperature is lower than –10 °C When the outdoor ambient temperature is below -5 °C , defrost control is automatically initiated every two hours. Defrost is terminated on the following conditions: • The time of defrost is 10 minutes • The condenser mid coil temperature is above 10 °C .
During cooling mode, the range of ambient temperatures can be from -5 to 43 °C . During the heating mode, the range of operation can be from -15 to 25 °C .
It is possible to change the size of the indoor board to fit a particular configuration. Please talk to the Copeland Application Engineer to discuss more details.
The room cooling or heating demand is a function of the difference between the room temperature and the set point temperature. As the room temperature starts getting close to the set point temperature, the electronic controller gives the signal to the compressor to reduce the capacity output. This process continues until it becomes a fine-tuning of capacity output.
The indoor coil need four sensors to measure the inlet refrigerant temperature, middle coil temperature, exit coil temperature and the return air temperature. The room demand is calculated from the set point temperature and the return air temperature. The coil inlet and exit temperature is required for superheat control during the cooling mode. The mid coil temperature and outlet temperature is required for sub-cooling control during the heating mode.
A fixed electronic expansion valve opening, though simple to control, does not provide optimum performance. If the opening is suboptimal, the performance of the system will also be suboptimal. A continuously changing electronic expansion valve will be able to respond to system changes much faster too.
During the heating mode, the indoor electronic expansion valves act like flow control device. It works in a way to ensure that the distribution of the refrigerant to different evaporators happens, according to the load requirements. The temperature sensors measure the sub-cooling on the coil, and this controls the indoor electronic expansion valve setting.
In case that the Pulse Width Modulation (PWM) valve fails, the system should stop and display some error (alarm) code on the PCB board (outdoor) and wired remote controller. This in unlikely scenario, as the solenoid valve is a specially designed high life valve. This valve has been designed to operate for 40 million cycles, which is equivalent to 30 years.