The Vital "Circulation Sentinel" in Air Source Heat Pumps

Water Flow Switch: The Vital "Circulation Sentinel" in Air Source Heat Pumps

⚙️ I. Core Function: Safeguarding System Integrity

The water flow switch acts as a real-time monitoring device in heat pump hydraulic systems. When circulating water flow drops below the safety threshold (typically ≤70% of rated flow), it immediately cuts off compressor power to prevent:

• Evaporator freeze cracks (in sub-zero environments) 9
• Compressor dry-burn damage (due to insufficient cooling)
• Efficiency collapse (COP degradation >40%) 16

🔬 II. Working Principle: Precision Sensing & Control

Mechanical Sensing Layer

• Paddle-Type Flow Switch: Water flow displaces a spring-loaded paddle (≥3mm displacement triggers signal) 2.
• Pressure-Differential Switch: Detects flow via Bernoulli's principle (pressure drop across pipe sections).

Electrical Control Logic

1. Sensor detects flow anomaly → Sends signal to controller.
2. Controller validates threshold breach → Activates relay.
3. Relay executes:
   • Compressor shutdown
   • Makeup water valve closure
   • Fault alarm activation

Critical Interaction: Flow interruption instantly halts refrigerant cycle, preventing phase-change failures in evaporators 9.

🛠️ III. Top 4 Fault Causes & Diagnosis Protocol

1. Valve Blockage/Closure
   • Symptom: Low flow despite pump operation.
   • Action: Verify all manual/automatic valves are fully open.
2. Pump Failure
   • New systems: Confirm pump capacity matches design specs.
   • Existing systems: Check for motor burnout, impeller jamming, or power loss 9.
3. Pipe Blockages
   • Focus areas:
     • Y-strainer clogging (primary culprit)
     • Mineral deposits in narrow-diameter pipes
   • Solution: Flush system with descaling agents.
4. Switch or Mainboard Malfunction
   • Diagnostic test:
     • Short-circuit flow switch terminals.
     • If fault persists → Mainboard error (replace PCB).
     • If fault clears → Switch sensor failure (replace unit).
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