In the world of refrigeration & air conditioning, selecting the right components can make or break the efficiency and reliability of your system. One such critical component is the relay that controls the operation of the compressor.
A mismatch here can lead to overheating, frequent breakdowns, or even system failure. So, how do you ensure you’re choosing the right one? The answer lies in understanding two key electrical parameters: LRA (Locked Rotor Amps) and FLA (Full Load Amps).
Understanding LRA and FLA
LRA (Locked Rotor Amps) This is the current drawn by the compressor at the moment it starts. It’s a surge — often several times higher than the running current — and represents the maximum amperage during full start-up conditions.
FLA (Full Load Amps) This is the current your compressor draws during steady-state, full-capacity operation. It’s what the system pulls under normal working conditions.
Why Relay Selection Matters
The relay acts as a gatekeeper, switching the compressor on and off with current flowing through it’s contacts. It must withstand both:
- The high inrush current (LRA) at startup
- The steady-state current (FLA) during operation
If the relay isn’t rated for these conditions, you risk premature failure of the relay — or worse, damage to your compressor.
Best Practices for Relay Selection
- Match Relay Rating to LRA Always choose a relay that can safely handle the peak start-up current. Underrated relays are a common cause of burnout.
- Account for FLA for Continuous Use Make sure the relay’s continuous current rating exceeds the compressor’s FLA to ensure long-term durability.
- Consult Manufacturer Guidelines Don’t guess. Always refer to the compressor’s data sheet and match it with relay specifications. Pay attention to voltage compatibility, environmental conditions, and relay type (electromechanical vs solid-state, etc.)
Final Thoughts
The relay may seem like a small component, but it plays a huge role in ensuring the safe and efficient operation of your refrigeration system. Selecting the right one means balancing both LRA and FLA, and always staying within the recommended specs.
By doing so, you not only protect your compressor but also boost system reliability and reduce maintenance costs.