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The solution of cooling or heating by means of an HVAC unit with direct evaporator/condenser allows to maintain the temperature in the conditioned space with a minimum hysteresis of +/- 2 °C (assuming proper design and subsequent commissioning).
Fans
are axial with air outputs of 1900 to 6960 m3/h. IP23 protection.
Compressors
DC Twin rotary with overload protection. Power control is provided by 3D DC Inverter.
Refrigerant
R 410a or R32. Refrigerant control by capillary tube with EEV. Connection via Cu pipe with fitting.
Regulation
Using the AHU-ELDES communication module, the condensing unit is controlled by the Digireg® control used in the DUOVENT® COMPACT and DUOVENT®MODULAR units. The AHU-ELDES_02 module is a communication box for LG units with the possibility of connecting Modbus communication or the optional Module of Power Limitation (MOV).
Operating Conditions
Ambient temperature for cooling -15°C to +48°C, for heating -18°C to +18°C.
Operation
As a matter of principle, HVAC units with heat recovery using an outdoor condensing unit as a heat pump in heating mode will ensure a sufficient supply temperature upstream of the evaporator coil (in normal operation and with appropriate controller settings). Supply HVAC units using an outdoor condensing unit as a heat pump in heating mode shall be equipped with a mixing damper to ensure a minimum temperature in front of the evaporator of +10 °C. Heat recovery HVAC units shall be equipped with a safety thermostat behind the evaporator (in front of the coil) to ensure that the condensing unit switches from cooling to heating mode when the temperature drops below +12 °C. It is also possible to fit an independent electronically adjustable temperature controller. The heat recovery HVAC unit must open the circulation damper in the event of receiving a DEFROST signal from the outdoor condensing unit. If such a solution is not possible for application reasons (restaurants, kitchens, healthcare, etc.), it can be solved to prevent the cold air supply by stopping the supply fan. If this option is also not applicable, the user must be aware that cold air will be supplied to the heated space during the defrost cycle. The primary risk to the HVAC unit is the possibility of the water heater or bivalent water heater circuit freezing in cooling mode. If a direct cooling unit design with water heating is proposed, the water heater must be located upstream of the DX chiller. When using a heat pump and water bivalence assembly, the best option is to use antifreeze to prevent freezing of the water circuit. If this alternative cannot be used, a year-round supply of heating water to the system upstream of the control valve must be provided so that frost protection functions are active. HVAC units without water heating do not need to address this issue. The heat pump has manufacturer-set protection process times (start-up time, minimum run time, minimum operating capacity and maximum number of switching times) and therefore sometimes the system response is not instantaneous and some delays and temperature overshoots into positive and negative values may occur.
Caution
The AHU-ELDES_02 module does not interfere with the control logic of the outdoor condensing unit. The control algorithms for compressor speed, condensing/evaporating temperature and condensing/evaporating pressure at the outdoor unit heat exchanger are contained in the outdoor condensing unit PCB software. The communication box does not replace the MaR HVAC unit in any way.
