Function and wiring specifications of compressor crankcase heater | Low temperature shutdown refrigerant migration protection scheme
The crankcase heater is a standard accessory for low-temperature piston compressors. It continuously heats the refrigeration oil during shutdown, separating the refrigerant dissolved in the oil to avoid liquid refrigerant impacting the cylinder during the next start-up.
The power of the heater is matched according to the size of the cylinder body. Small four cylinder models are generally equipped with 80W heating belts, while medium four cylinder and large four cylinder models use 120W~160W specifications to maintain a continuous oil temperature of 25 ℃~35 ℃.
The Xitelide low-temperature semi enclosed unit has reserved heater wiring terminals at the factory. The heater is independently powered and not controlled by the compressor contactor. It continues to work even after power failure and shutdown.
Heater failure is a hidden and frequent fault in low-temperature units, with no obvious alarm on the surface. The fault is concentrated in the occurrence of suction with liquid and liquid hammer damage to valve plates within a few minutes of each start-up.
For machine rooms with ambient temperatures below 10 ℃, the crankcase heater must be continuously operated throughout the year; The medium to high temperature preservation unit in the computer room that is above 25 ℃ all year round can omit this accessory in some scenarios.
The heater wiring must be connected in series with a temperature control switch. If the oil temperature exceeds 45 ℃, it will automatically shut off to prevent heating loss of control. If the oil temperature is too high, it will accelerate the oxidation of the refrigeration oil and the rapid increase of the oil acid value.
Many construction sites find it troublesome to debug without connecting the crankcase heating, and short-term trial runs do not show any problems. After repeated start stop and nighttime shutdown, the liquid hammer failure rate increases by more than three times.
Exporting to high-altitude mountainous cold storage projects with huge temperature differences between day and night, the customer's power supply is unstable, and the purchaser needs to be reminded that if the power is cut off for more than 8 hours, manual preheating is required before restarting.
Screw refrigeration compressors also require crankcase heating, and screw compressors have a larger oil storage capacity. The heater power is about 40% higher than that of piston compressors with the same cooling capacity.
The refrigeration maintenance inspection checklist should include a heater detection item, measure the heating resistance in the shutdown state, and if the resistance is infinite, it means that the heating wire is burnt out, and the parts need to be replaced in a timely manner.
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FAQ
What is the core function of the crankcase heater? Release the refrigerant dissolved in the refrigeration oil to prevent liquid return during startup.
2. What is the standard power of the heater for small four cylinder models? The mainstream configuration is an 80W crankcase heating belt.
3. Is the crankcase oil temperature maintained within the target range? Maintaining a temperature range of 25 ℃ to 35 ℃ is an appropriate range.
4. Typical fault phenomena of heater failure? It is easy for the liquid to return and cause liquid hammer failure every time it is turned on.
5. Should there be a heater in the high-temperature warehouse with high temperature in the computer room? Most stable high-temperature machine rooms can be omitted.
6. Does the heater start and stop synchronously with the compressor? Independent power supply, continuous heating after shutdown.
What are the risks of restarting after a long power outage? The oil temperature drops, and a large amount of refrigerant dissolves into the oil, making it highly susceptible to liquid hammer.
