AS3 free chlorine sensor

Monitoring – Hospital Hot Water System

A Tier-3 hospital (180,000 m², 1,200 beds) operates a centralized hot water system supplying over 600 m³/day across 4,200 outlets. To meet healthcare hygiene standards, sodium hypochlorite disinfection is applied, maintaining free chlorine at 0.05–0.5 mg/L.

< 0.05 mg/L: Risk of Legionella growth (previous pneumonia cases reported)
> 0.5 mg/L: Skin/mucosal irritation risk, especially for NICU and post-surgical patients
Excess chlorine also accelerates pipeline corrosion
Challenge: Manual Testing Limitations

Previously, the hospital used DPD manual sampling twice daily, causing serious blind spots:

Morning peak (7–9 AM): chlorine dropped below 0.03 mg/L due to high demand
Night stagnation (0–6 AM): levels fell to ~0.02 mg/L
Measurement delay up to 2 hours → no real-time dosing adjustment
Solution: AS3 free chlorine sensor Real-Time Monitoring System

The hospital installed the German AS3 free chlorine sensor (AS3H-CL-M12) to enable continuous monitoring and closed-loop dosing control.

Key features:

Measurement: 0.005–2.000 mg/L
Resolution: 0.001 mg/L
Temperature: 0–70 °C
Response time: ~30 s
Material: PEEK housing (high chlorine & heat resistance)
Protection: IP68, M12 connector

Stable operation under hospital conditions (50–55 °C, pH 7.0–7.5).

Installation & System Integration

Installed in the main circulation line (12 m downstream of dosing point) with full mixing.

System configuration:

Flow cell (20 L/h stable flow)
316L stainless steel protection sleeve
50 μm filtration unit

Integrated into Building Automation System (BA) for automatic dosing control.

Automated Control Logic
< 0.05 mg/L: Increase dosing pump output
0.05–0.5 mg/L: Maintain optimized intermittent dosing
> 0.5 mg/L: Reduce dosing + add softened water dilution
Maintenance & Data Management
Weekly calibration (DPD reference method)
Electrolyte replacement every 4 months
Membrane cap replacement yearly
Data (chlorine, temperature, pH) automatically uploaded to HIS and stored for 5 years
Results (After 12 Months)
100% compliance with chlorine standards
Legionella detection reduced from 22% → 0%
NICU irritation complaints: eliminated
Disinfectant consumption reduced by 17.9%
Annual savings:
~$17,000 maintenance
~$8,300 labor cost
Outcome

The system significantly improved hospital water safety, efficiency, and regulatory compliance. The AS3 free chlorine sensor enables real-time monitoring, automated dosing, and full traceability, making it a reliable solution for healthcare hot water systems in hospitals, nursing homes, and similar facilities.