What is FLA,RLA,LRA, in Compressor? LRA Keya hota hai

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Understanding LRA, FLA, and RLA in Compressors - Full Guide
Welcome to MK Technical Solutions, where we explain HVAC and electrical concepts in a simple and practical way. In this video, we will break down the meaning of LRA, FLA, and RLA in compressors, why they are important, and how to calculate them correctly.
If you work with air conditioning (AC) and refrigeration systems, understanding these terms will help in troubleshooting compressor problems and selecting the right electrical components for HVAC systems.
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1. What Are LRA, FLA, and RLA in a Compressor?
LRA - Locked Rotor Amps
LRA is the maximum current a compressor motor draws when it starts. This happens when the rotor is locked (not rotating), and the motor is trying to start from a complete stop.
✔ Why is LRA important?
Helps in selecting the correct circuit breakers and overload protectors.
Indicates potential starting issues in compressors.
High LRA can cause breaker trips or wiring damage if not properly controlled.
✔ How to Reduce LRA?
Use a soft starter or VFD (Variable Frequency Drive).
Install a start capacitor and relay for better startup performance.
Ensure proper voltage and wiring to prevent excessive current draw.
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FLA - Full Load Amps
FLA is the current drawn by the compressor when operating at full load under normal conditions. This value is listed on the compressor nameplate.
✔ Why is FLA important?
Used to size wiring, contactors, and fuses in HVAC systems.
Helps determine power consumption and efficiency.
Ensures the compressor is running within safe electrical limits.
✔ How to Calculate FLA?
Example:
A 5 HP (Horsepower) compressor running at 220V, with 90% efficiency:
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RLA - Rated Load Amps
RLA is the manufacturer’s recommended operating current for the compressor under normal conditions. Unlike FLA, RLA is not a direct electrical measurement but a calculated value.
✔ Why is RLA important?
Helps in setting up overload protection for the compressor.
Ensures the compressor does not run beyond safe limits.
Used in HVAC troubleshooting to detect faulty compressors.
✔ How to Calculate RLA?
Manufacturers typically use this formula:
Example:
If the FLA is 18.9A, then:
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2. Key Differences Between LRA, FLA, and RLA
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3. Why Are These Values Important in HVAC Systems?
1. Protecting the Compressor
Knowing LRA, FLA, and RLA helps prevent burnt windings, overheating, and breaker trips.
If a compressor exceeds FLA or RLA, it may indicate a mechanical or electrical issue.
2. Sizing Electrical Components Correctly
Breakers & Fuses: Must be rated above FLA but below LRA to prevent unnecessary trips.
Contactors & Relays: Should match the RLA or slightly higher for safe operation.
3. Diagnosing HVAC Compressor Problems
If your compressor is tripping the breaker or overheating, compare the actual ampere draw with FLA and RLA:
✔ If the current exceeds RLA: The compressor is overloaded or faulty.
✔ If the current is far below RLA: The compressor may not be running efficiently.
✔ If the compressor is drawing LRA constantly: It is stuck and may need replacement.
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4. How to Measure Compressor Amps?
Step 1: Use a Clamp Meter
Set the meter to AC Amps mode.
Clamp it around the power wire connected to the compressor.
Read the ampere draw while the compressor is running.
Step 2: Compare with Nameplate Values
Check the FLA and RLA on the compressor nameplate.
If the running current is too high, check for dirty coils, low refrigerant, or a failing motor.
Step 3: Inspect Startup Current
If the compressor draws LRA for more than 2-3 seconds, it may have a stuck rotor or capacitor failure.
Test the start capacitor and contactor for faults.
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5. Preventive Maintenance Tips for Compressors
✔ Regularly clean condenser coils to maintain proper cooling efficiency.
✔ Check and replace capacitors if the compressor struggles to start.
✔ Ensure proper voltage supply to avoid electrical stress on the compressor.
✔ Use a soft starter or VFD for smooth compressor operation and longer lifespan.
✔ Monitor ampere draw periodically to detect early signs
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7. Why Choose MK Technical Solutions?
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Conclusion
Understanding LRA, FLA, and RLA in compressors is essential for HVAC technicians, electricians, and engineers. These values help in troubleshooting, selecting electrical components, and ensuring the safe operation of the compressor.
If you have any questions, leave a comment below, and we’ll be happy to help!
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