Cooling Operation
| Compressor capacity control | Constant evaporation temperature (Te) control (Basic target value: R22 = 5.5°C, R407C = 7.5°C, R410A = 6°C *Compensation is applied) |
| Indoor electronic expansion valve control | Constant superheated degree (SH = Tg – Tl) control (Basically compensation of 5°C is required. As to R407C unit, temperature gradient compensation is applied.) |
| High pressure stepping down control | As rising of the high pressure, decreased the compressor capacity. |
| High pressure protection control | Forcedly thermostat-off with limitation on retrying |
| Low pressure stepping down control | Low pressure stepping down control is not made. (Capacity is decreased by normal control of compressor.) |
| Low pressure protection control | Hot gas bypass is on. ? Forcedly thermostat-off with limitation on retrying |
| Low outdoor temperature cooling control | As lowering of the high pressure, outdoor fan is controlled. (fan-tap drops). |
| Cooling overload control | Instruction of forcedly opening degree is given to indoor electronic expansion valve. (Disregard of superheated degree control, even opening degree) |
| Discharge pipe temperature control | Based on discharging pipe temperature Td and discharging superheated degree DSH = Td – Tc, Injection is on. ? Compressor capacity is lowered.? Forcedly thermostat off with limitation on retrying |
| Oil return control | Based on cumulative operation time, oil return operation should be carried out periodically. (According to the state of operation, cumulative operation time may be compensated.) |
Heating Operation
| Compressor capacity control | Constant condensing temperature (Tc) control (Basic target value: R22 = 46°C, R407C = 48°C, R410A = 46°C *Compensation is applied) |
| Outdoor motorized valve control | Constant superheated degree (SH = Ts – Te) control (Basic 5 deg. compensation is applied.) |
| Indoor motorized valve control | Constant subcooled degree (SC = Tc – Tl) control (Basic compensation of 5 deg is applied.) |
| High pressure stepping down control | (= Heating overload control) Compressor capacity control ? Outdoor electronic expansion valve control (Disregard of superheated degree control) and Outdoor fan control (Fan tap is lowered.) |
| High pressure protection control | Forcedly thermostat-off with limitation on retrying |
| Low pressure stepping down control | As lowering of the low pressure decreases the compressor capacity. |
| Low pressure protection control | Hot gas bypass is on. ? Forcedly thermostat-off with limitation on retrying |
| Defrost control | Based on lowered Tb, defrosting operation is carried out. (Compensation based on Ta). |
| Discharge pipe temperature control | Based on discharging pipe temperature Td and discharging superheated degree DSH = Td – Tc, Injection is on. ? Compressor capacity is lowered ? Forcedly thermostat-off with limitation on retrying |
| Oil return control | Based on cumulative operation time, oil return operation should be carried out periodically. (According to the state of operation, cumulative operation time may be compensated.) |
