Cold storage compressor oil pressure difference alarm and low pressure alarm distinction | Fault phenomenon, troubleshooting sequence, false alarm avoidance
The oil pressure difference alarm represents insufficient lubrication and oil supply of the compressor, while the low pressure alarm represents low refrigerant pressure on the evaporation side. The two types of alarm protection logic, triggering conditions, and risk levels are completely different, and it is easy to confuse them on site.
Oil pressure differential protection is the protection of the compressor body, only for oil pump supply, with a shutdown delay of generally 60 seconds; Low voltage protection belongs to system side protection, targeting evaporation pressure, with a delay of 30-60 seconds to avoid fluctuations in startup pressure.
The controller of the Xitelidou semi enclosed unit will distinguish alarm codes. After the oil pressure difference alarm is locked, it will prioritize prohibiting restart to prevent bearing dry wear; Most low voltage alarms can be automatically reset, with only repeated alarm locking.
Typical phenomena of oil pressure difference alarm: dirty and clogged oil filter, high viscosity of refrigeration oil, worn oil pump, low oil level, failure of crankcase heater, inability to establish oil pressure during cold start-up; The storage temperature may not necessarily be too high.
Typical phenomena of low pressure alarm: refrigerant leakage, expansion valve blockage, insufficient liquid supply, frosting and freezing of evaporator; With the continuous decrease in evaporation pressure, the storage temperature cannot be lowered, and the degree of superheat of the return gas is relatively high.
Many maintenance technicians reset the alarm directly when they see it, but cannot distinguish the type: oil pressure difference alarm. It is strictly prohibited to repeatedly test the machine, as each start may cause the crankshaft and connecting rod bearings to pull the cylinder; Low pressure alarm can be reset once to observe pressure changes.
Parallel units are most likely to confuse two types of alarms, with one head reporting a pressure difference and the other heads reporting normal pressure; Low pressure alarm in the main pipeline, synchronized pressure drop in all machine heads.
A separate alarm comparison table shall be created in the technical manual of foreign trade projects, with codes, risk levels, and prohibited operation items marked for local electricians to reduce the probability of compressor damage caused by overseas misoperation.
Sensor failure can also cause false alarms: the oil pressure difference sensor's capillary tube is blocked and reports an oil pressure difference; Low pressure sensor ice blockage, virtual connection of circuit, triggering false low pressure alarm.
Maintenance and troubleshooting sequence: First check the alarm code, prioritize checking the oil level, oil temperature, oil filter, and oil pump for oil pressure difference; Priority should be given to checking the refrigerant volume, expansion valve, evaporator frosting, and pipeline leaks for low pressure.
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FAQ
What type of protection does the oil pressure difference alarm belong to? Compressor lubrication body protection.
Can the oil pressure difference alarm be reset and tested multiple times? Not recommended, it is very easy to pull the cylinder.
3. Where is the main problem with low voltage alarm? Insufficient or leaking refrigerant supply on the evaporation side.
4. Characteristics of low voltage alarm in parallel unit header? The evaporation pressure of all machine heads is synchronously low.
5. What is the reason for the easy reporting of oil pressure difference when starting up in a cold state? Low oil temperature and high viscosity of refrigeration oil.
6. Common causes of false low voltage alarms? Pressure sensor ice blockage and virtual connection of the circuit.
Which is more risky, oil pressure difference or low pressure alarm? Oil pressure difference alarm, faster damage speed.
