Brand New Original Hitachi 403DH-64C1, 453DH-72C1, 303DH-47C1, 303DH-50C1, 353DH-56C1, 400DHM-64D1(2), 500DHM-80D1(2), 600DHM-90D1(2) Refrigeration

Start-Stop and Mechanical Strength: The biggest challenge for fixed-frequency units is the risk of liquid slugging and high-current thermal shock during frequent start-stop cycles. This series reinforces the lower bearing support structure, adopting heavy-duty ball bearings to replace the light-load plain bearings used in inverter units, enabling it to withstand torque shocks 5 to 7 times higher than the rated current at the instant of startup. An extra-large capacity oil sump is designed at the bottom of the housing to ensure that the lubricating oil supply remains unaffected by the frequency of start-stop cycles during long-term continuous operation (such as 24-hour cold chain logistics).

Electrical Fault Tolerance: Unlike the inverter series which is sensitive to harmonics, this series is directly connected to the utility grid and has extremely strong tolerance to voltage dips and three-phase imbalance. Even in remote industrial areas with voltage fluctuations of up to ±15%, it can still maintain rated cooling capacity output without frequency derating protection or shutdown due to low voltage.

Maintenance and Spare Parts Logic: With the complex variable frequency drive (VFD) board removed, there are very few failure points. In large-scale industrial refrigeration scenarios (such as ice machines and blast freezing tunnels), maintenance personnel only need to measure winding resistance and insulation resistance to quickly troubleshoot faults. The on-site replacement cycle is short, and spare parts have extremely high universality. Models with the DHM suffix focus on the transitional replacement of R22 refrigerant. Their displacement design is specifically matched to the lower volumetric efficiency of alternative refrigerants, ensuring no cooling capacity degradation after refrigerant conversion.

Freezing, Refrigeration, and Cold Storage: Widely applicable to scenarios requiring long-term constant compressor output, such as low-temperature refrigeration warehouses, freezers, ice machines, and blast freezing tunnels. The fixed-frequency design ensures stable operation under constant loads, avoiding the poor oil return issue of inverter units in the low-frequency range.

Industrial Refrigeration Equipment: Serves industrial refrigeration processes such as food processing, chemical cooling, and pharmaceutical refrigeration. The heavy-duty bearings and extra-large oil sump design can withstand the mechanical shock caused by frequent start-stop cycles.

Commercial Refrigeration Systems: Suitable for commercial refrigeration scenarios such as supermarket freezers, convenience store refrigerated display cases, and restaurant kitchen cold rooms.

VRF Air Conditioning After-Sales Replacement: Some models can also be used for the maintenance and replacement of fixed-frequency units in VRF air conditioning systems, but their core advantage remains concentrated in constant-output scenarios for refrigeration rather than heating.

Liquid slugging — A large amount of liquid refrigerant enters the compressor. Due to the incompressibility of liquids, the instantaneous high pressure causes the scroll plates to shatter.

Impurities entering — Welding slag from system piping, burrs from component machining, metal particles from wear of moving parts, etc., enter the compression chamber.

Moisture ingress — The system was exposed for too long during installation, leading to moisture intrusion.

Check if the system refrigerant charge exceeds the standard, or if refrigerant has flowed back to the bottom of the compressor after being left unused overnight.

It is recommended to add a crankcase heater (preheating belt) at the bottom of the compressor, and turn it on 6 hours before startup to evaporate the refrigerant at the bottom.

The system piping must be purged clean with nitrogen, and the matching drier filter must be replaced.

After replacing the compressor, it is recommended to replace the drier filter again after the unit has been running for one week.

Poor lubrication — Excessive system refrigerant, excessive liquid return, frequent starts, or foreign objects entering cause oil film rupture.

Insufficient system refrigerant or compressor reverse rotation — Causes abnormally high temperatures at the center of the scroll, and the bottom of the orbiting scroll heats up rapidly.

Moisture ingress into the system — Causes rust spots on parts, leading to wear.

Ensure that the lubricating oil is sufficient and of qualified quality — The oil level should be visible from the sight glass, but should not exceed half.

Check the system refrigerant charge to avoid too much or too little.

Confirm that the compressor wiring phase sequence is correct (three-phase T1, T2, T3 wired in a clockwise direction).

Avoid frequent start-stop cycles of the compressor.

Pressure too high: Intake valve failure, hydraulic cylinder failure, load solenoid valve failure, pressure set too high.

Pressure too low: Actual gas consumption is greater than the unit output, system leakage, pressure set too low.

Check and clean the oil cooler, replace the oil filter element.

Check whether the thermostat valve and oil cut-off solenoid valve are working properly.

Check whether the exhaust duct is unobstructed and whether the ambient temperature is within the specified range (38°C or 46°C).