Aermec BP2

What does Aermec BP2 mean?

The GR3 controller on NRL, NRA, NRC, NBW and NLW chillers has shut down refrigerant circuit 2 because the low-pressure protection tripped (digital pressure switch or the low-pressure transducer, factory alarm threshold All. BP +2.0 bar, with a 180 s startup bypass). Per the service manual, each alarm stops its own circuit only — the other circuit keeps running.

Symptoms

• Circuit 2 compressor stopped while the other circuit continues
• Alarm shown on the GR3 panel with the alarm relay energized
• Reduced cooling/heating capacity from the unit
• Trips shortly after compressor start once the 180 s bypass expires

Common causes

• External cold conditions at the evaporator side
• Low refrigerant charge in the circuit
• Trip window interactions: the block is bypassed during defrosting and for 180 s from compressor start

Diagnostic steps

1. 01

   Read the alarm on the GR3 panel

   Identify which circuit tripped (AP1/BP1 = circuit 1, AP2/BP2 = circuit 2); the manual notes the alarm history is stored.

2. 02

   Check the evaporator/charge side

   Verify refrigerant charge and check operating conditions against the unit's limits.

3. 03

   Verify operating limits

   Confirm external temperature and water conditions are inside the unit's declared operating envelope.

4. 04

   Check the pressure device

   Low-pressure transducer is 0–30 bar for R410A (spare part 9103742).

5. 05

   Reset and monitor

   After removing the cause, reset the alarm and monitor the circuit pressures through a full cycle.

When to call a professional

Pressure protections on these chillers guard the compressor and the refrigerant circuit. If the alarm returns after clearing the obvious airflow or operating-limit causes, or any work on the refrigerant circuit or the pressure devices is needed, hand off to a licensed refrigeration technician — the service manual directs unresolved anomalies to Aermec's service network.