The 22HL-50 is a Belimo leakage switch for detecting liquid leaks in HVAC and building applications: false floors, suspended ceilings, mechanical rooms, server room sub-floors, AHU drain pans, container monitoring, and any installation where unintended water or water-glycol presence requires alarm or control response. The sensor uses point detection via electrodes on the housing — the sensor itself detects liquid by contact with its electrode pins, with a conductivity threshold of approximately 10 µS — sensitive enough for clean water but immune to humidity and ambient moisture. Output is one SPDT changeover relay with dry contact rated for max. 1 A switching current at 24 V — wires directly into a controller alarm input, or in series with a Belimo shut-off valve to interrupt water flow automatically when a leak is detected. The unit features an on-housing LED indicator (green for power OK, red for active leak detection) and automatic reset after the sensing contacts dry — no manual reset required after a transient event. The polycarbonate housing (transparent top cover for LED visibility, orange UL94 5VA bottom) is rated NEMA 4 / IP65 for wet and washdown environments. A 1/2" NPT conduit adapter ships with the unit for direct connection to standard electrical conduit.
Point leak detection at a known potential leak location — AHU drain pans, condensate trap overflows, equipment skid bases, boiler room floor low-points. The single SPDT relay wires directly to a controller alarm input, or in series with a Belimo motorized shut-off valve to interrupt water supply automatically. Other 22HL variants: 22HL-502 (dual relay output), 22HL-505 (16.4 ft cable detection), 22HL-520 (65 ft cable detection).
The on-housing LED gives a clear visual status without needing to check the BAS: green when powered and sensing normally, red when liquid is detected at the sensing contacts. The transparent polycarbonate top cover lets the LED be read at a glance during walkthroughs or service calls. The unit automatically resets to green once the contacts dry — no manual reset, no field re-arming.
Key Features
Conductivity-based liquid detection at the sensor electrodes — install at specific known potential leak locations (AHU drain pans, condensate trap overflows, equipment skid bases, low-point floor drains) for fast trigger on real leak events. Compact, surface-mount form factor for easy installation.
Detection triggers at approximately 10 µS conductivity — sensitive enough to detect tap water and water-glycol mixtures, but immune to ambient humidity and condensation on the housing exterior. The sensing contacts respond to actual liquid presence, not damp air.
Green LED indicates normal power-on operation; red LED indicates active leak detection. Visible through the transparent PC top cover — facility staff and service technicians can verify sensor status at a glance without checking the BAS or opening the housing.
The relay returns to normal state automatically once the sensing contacts dry. No manual reset button, no field re-arming after a transient event — particularly valuable for installations where access is difficult (suspended ceilings, sub-floors) or where leak events may be brief and self-clearing.
Single dry-contact relay output — max 1 A switching current at 24 V, min 3 mA at 10 V. Wires directly to controller alarm inputs, Belimo motorized valve coils (for direct in-series shut-off), or third-party annunciator panels. Dry contact (no internal power source) — installer supplies the load-side voltage.
Transparent polycarbonate top cover (for LED visibility) with orange UL94 5VA polycarbonate bottom, sealed with NBR70 gasket. UV-resistant for installations near exterior light. Rated NEMA 4 / IP65 for wet and washdown environments — appropriate for the leak-detection application where the sensor itself may be exposed to the liquid it's monitoring for.
Compatible with standard 24V control transformers shared with actuators and other sensors. AC 21.6-26.4V or DC 13.5-26.4V supported. Power consumption: 1.5 VA AC / 0.6 W DC — very low draw.
Conduit adapter ships in the box for direct connection to standard 1/2" NPT electrical conduit. Cable gland with strain relief supports ø6-8 mm cable diameter for installations without conduit. Pluggable spring-loaded terminal block (max 2.5 mm²) for sensor and load-side wiring.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Liquid leak detection switch |
| Measured Value | Liquid presence (conductivity-based) |
| Measuring Fluid | Water, water-glycol mixtures |
| Sensing Principle | Conductivity |
| Switching Threshold | ≈10 µS |
| Detection Method | Point detection (electrodes on housing) |
| Output Type | 1× SPDT changeover dry contact |
| Max Switching Current | 1 A @ 24 V |
| Min Switching Current | 3 mA @ 10 V |
| Reset | Automatic after contacts dry |
| Display | LED — Green (power OK), Red (leak/liquid present) |
| Power Supply | 24 VAC/VDC (AC 21.6-26.4V / DC 13.5-26.4V) |
| Power Consumption | 1.5 VA AC / 0.6 W DC |
| Electrical Connection | Pluggable spring-loaded terminal block, max 2.5 mm² |
| Cable Entry | Cable gland with strain relief, ø6-8 mm; 1/2" NPT conduit adapter included |
| Housing — Top Cover | Polycarbonate, transparent (UV resistant, UL94 5VA) |
| Housing — Bottom | Polycarbonate, orange (UV resistant, UL94 5VA) |
| Housing Seal | NBR70, black |
| Cable Gland | PA6, black |
| Enclosure Rating | NEMA 4 / IP65 |
| Protection Class | IEC/EN III, PELV (Protective Extra-Low Voltage) |
| Pollution Degree | 3 |
| Type of Action | Type 1.B |
| Rated Impulse Voltage | 0.8 kV |
| Ambient Temperature | -4 to 158°F (-20 to 70°C); brief excursion to 185°F (85°C) max 10 minutes |
| Fluid Temperature | -4 to 158°F (-20 to 70°C) |
| Ambient Humidity | Max. 95% RH, non-condensing |
| EU Conformity | CE Marking |
| Certification | IEC/EN 60730-1 |
| Quality Standard | ISO 9001 |
| Manufacturer | Belimo |
| Manufacturer Part Number | 22HL-50 |
| Warranty | 5-year factory warranty |
What's In the Box
- 22HL-50 leakage switch in transparent/orange polycarbonate housing (with point-detection electrodes on housing)
- 1/2" NPT conduit adapter
- Cable tie
- Mounting dowels
- Mounting screws
Documentation
Frequently Asked Questions
What does the 22HL-50 detect and how does it signal a leak?
It detects the presence of liquid (water or water-glycol mixtures) via conductivity sensing at the sensing contacts, with a threshold of approximately 10 µS. Detection happens at electrodes on the sensor housing itself — install where you expect a leak to land. When liquid is detected, the SPDT relay activates, changing state from normal to alarm position. The on-housing red LED illuminates to show the alarm condition visually. After the sensing contacts dry, the unit automatically resets — no manual intervention needed.
Where should I install this sensor?
On a flat surface at the lowest point of a known leak risk area. Common locations: AHU drain pans (mount on the pan floor near the drain), boiler/chiller room low-point floor drains, condensate trap overflow zones, equipment skid bases under pumps and valve assemblies, and water-cooled equipment bases. The point-detection electrodes need to actually contact pooled water to trigger — install where water would naturally collect, not on a vertical surface or elevated position.
What media can this sensor detect?
Water and water-glycol mixtures — anything with conductivity above the ~10 µS threshold. This includes essentially all hydronic system fluids (chilled water, hot water, condenser water, glycol loops). The sensor will NOT reliably detect: deionized water (too low conductivity), oils, refrigerants, fuels, or non-conductive solvents. For oil or fuel leak detection, a different sensing technology is required (typically optical or hydrocarbon-specific). Operating fluid temperature range is -4 to 158°F (-20 to 70°C).
How is the relay output wired?
SPDT (Single Pole Double Throw) changeover dry contact — three terminals: Common (C), Normally Open (NO), Normally Closed (NC). The relay is a passive dry contact, no internal voltage source. Wire the load circuit's voltage through C and NO (for normally-open behavior — circuit closes on alarm) or through C and NC (for normally-closed behavior — circuit opens on alarm, fail-safe). Max switching current is 1 A at 24 V; min is 3 mA at 10 V. Use NC wiring for fail-safe applications where loss of sensor power should also trigger the alarm condition.
Does the sensor reset automatically after a leak event?
Yes. After the sensing contacts dry (no longer detect conductive liquid), the relay automatically returns to normal state and the LED returns to green. No manual reset button to press, no field re-arming required. This is particularly valuable for installations in hard-to-access locations (suspended ceilings, sub-floors) where a manual-reset sensor would require an extra service call after every transient event. If the BAS needs to record the alarm event for audit purposes, the controller should latch the alarm signal internally — the sensor's own reset is automatic and doesn't preserve event history.
How does this differ from the other 22HL variants?
All 22HL variants share the same chassis, conductivity sensing principle, auto-reset behavior, NEMA 4 / IP65 housing, and 24 VAC/VDC power. The differences are: 22HL-50 = point detection on housing, 1× SPDT 1A relay; 22HL-502 = point detection, 2× SPDT 3A relays (dual, isolated); 22HL-505 = 16.4 ft (5 m) rope/cable detection, 1× SPDT; 22HL-520 = 65 ft (20 m) rope/cable detection, 1× SPDT. Choose point detection for known leak locations (drain pans, equipment bases); choose rope detection for extended areas (server rooms, data center sub-floors). Choose the dual-relay 22HL-502 when you need simultaneous valve-shutoff and BAS-alarm actions from a single sensor.
Does it need 24V power?
Yes. 24 VAC or 24 VDC supported (AC 21.6-26.4V / DC 13.5-26.4V). Power consumption is 1.5 VA AC / 0.6 W DC — very low draw, compatible with standard 24V control transformers shared with actuators and other sensors. Note that the relay output is a dry contact (passive) — the supply voltage to the load circuit must be provided externally.
- Sensor Type:
- Leakage Switch / Liquid Detection
- Sensing Principle:
- Conductivity
- Switching Threshold:
- ≈10 µS
- Compatible Media:
- Water / Water-Glycol Mixture
- Detection Method:
- Point (electrodes on housing)
- Output Type:
- 1× SPDT changeover dry contact
- Number of Relays:
- 1
- Max Switching Current:
- 1 A @ 24 V
- Reset Type:
- Automatic (after contacts dry)
- Display:
- LED (Green / Red)
- Power:
- 24 VAC/VDC
- Power Consumption:
- 1.5 VA AC / 0.6 W DC
- Conduit:
- 1/2 NPT (included)"
- Housing Material:
- Polycarbonate (transparent top + orange bottom)
- Seal Material:
- NBR70
- Enclosure:
- NEMA 4 / IP65
- Mounting:
- Surface (wall/floor)
- Supported Protocols:
- Dry contact relay (no bus, no analog)
