The 22WP-536 is a Belimo active 24V pressure sensor for liquids — designed for water, water-glycol mixtures, refrigerants, and other non-aggressive gases in HVAC systems. The sensor covers a High (0–100 psi) measuring range with 4-20 mA active output. The sensing element is a strain gauge on a stainless steel membrane with <±0.5% FS accuracy at 70°F (slightly relaxed across the wider operating temperature envelope) and ±0.1% per year long-term stability. The stainless steel 1.4301 housing with FKM (silicone-free) seal is rated IP65 / NEMA 4 and survives operating ambient from -40 to 221°F. The 1/4" NPT pressure connection threads directly into standard hydronic tappings, and the MVS plug (DIN EN 175301-803 Type A) electrical connector accepts 0.5–1.5 mm¬≤ wire. Burst pressure tolerance is 300 psi — 3× the high end of the measuring range — protecting the sensor from transient overpressure events common in hydronic systems (pump starts, sudden valve closures, water hammer).
Pressure monitoring on liquid HVAC systems where the working pressure falls in the 0–100 psi range: high-rise hydronic risers, district energy loops, chiller plant primary pumps, condenser water systems. For the same pressure range with 0-10V output instead (useful for long cable runs or controllers preferring current loops), see 22WP-516. Same output style, other ranges: 22WP-531 (Low (0–15 psi)), 22WP-534 (Medium (0–50 psi)).
Key Features
Active 4–20 mA output is immune to voltage drop on long cable runs (useful when the sensor is more than ~150 ft from the BAS panel) and has built-in fault detection: a reading of 0 mA means the loop is broken (vs 0V on a voltage output, which could mean either zero reading OR broken wiring). DC-only power (13.5–26.4 VDC).
Welded stainless steel housing with FKM (Viton-class) seal, silicone-free — compatible with refrigerants, hot water, chilled water, and water-glycol mixtures where silicone outgassing would contaminate the medium. IP65 / NEMA 4 rated for wet and washdown environments.
<±0.5% FS (Full Scale) accuracy at 70°F (21°C), <±1.5% FS across the 14-122°F operating range, <±2% FS across the full -40 to 221°F range. Long-term stability ±0.1% per year — no field calibration required for the lifetime of the sensor.
Burst pressure tolerance of 300 psi — 3× the high end of the measuring range. Survives transient overpressure events from pump starts, sudden valve closures, and water hammer without sensor damage or calibration drift. Negative overpressure tolerance -1 bar (-14.5 psi) handles vacuum-side transients from pump cavitation events.
Rated for water, water-glycol mixtures (any concentration), refrigerants, and non-aggressive gases. Steam inlet acceptable up to 100 kPa (15 psi). FKM seal and stainless steel wetted parts compatible with all common HVAC heat-transfer fluids. Open-loop systems are acceptable (unlike ultrasonic flow sensors which require closed-loop).
Standard 1/4" male NPT thread on the pressure port — installs into any standard hydronic tee or pressure tap without adapters. Use thread sealant (PTFE tape or pipe dope rated for the fluid temperature) on installation.
<0.6 W DC (4-20 mA loop) — compatible with standard 24V control transformers shared with actuators and other sensors. DC 24V only (13.5-26.4 VDC) — 4-20 mA loop requires DC supply.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Active pressure sensor for liquids and non-aggressive gases |
| Measured Value | Relative pressure (gauge pressure vs atmospheric) |
| Measuring Fluid | Water, water-glycol mixtures, refrigerants, steam (≤100 kPa / 15 psi inlet), non-aggressive gases |
| Sensing Element | Strain gauge on stainless steel membrane |
| Output Signal | 1× active analog: 4-20 mA current loop |
| Pressure Measuring Range | 0–100 psi |
| Overpressure Tolerance (Positive) | 200 psi |
| Overpressure Tolerance (Negative) | -1 bar (-14.5 psi) — handles pump cavitation transients |
| Burst Pressure | 300 psi — 3× nominal range |
| Pressure Accuracy at 70°F | <±0.5% FS (Full Scale) |
| Pressure Accuracy 14–122°F | <±1.5% FS |
| Pressure Accuracy -40–221°F | <±2% FS (full operating envelope) |
| Long-Term Stability | ±0.1% FS per year |
| Typical Response Time | max. 2 ms |
| Power Supply | DC 24V only (DC 13.5-26.4V) — 4-20 mA loop requires DC supply |
| Power Consumption | <0.6 W DC (loop-powered) |
| Electrical Connection | MVS plug per DIN EN 175301-803 Type A, accepts 0.5-1.5 mm² wire |
| Pressure Connection | 1/4" NPT (external thread) |
| Housing Material | Stainless steel 1.4301 (304 stainless) |
| Seal Material | FKM fluororubber (Viton-class), silicone-free |
| Enclosure Rating | NEMA 4 / IP65 (suitable for wet and washdown environments) |
| Protection Class | IEC/EN III, PELV (Protective Extra-Low Voltage) |
| Ambient Temperature | -40 to 221°F (-40 to 105°C) |
| Fluid Temperature | -40 to 255°F (-40 to 125°C) — frost protection required below 36°F (2°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 | 22WP-536 |
| Warranty | 5-year factory warranty |
What's In the Box
- 22WP-536 liquid pressure sensor in stainless steel housing with FKM seal
- MVS plug electrical connector (DIN EN 175301-803 Type A)
Note: thread sealant (PTFE tape or pipe dope rated for the working fluid temperature) is NOT included — use installer-supplied sealant rated for the specific medium and temperature.
Documentation
Frequently Asked Questions
What does the 22WP-536 measure and output?
It measures gauge pressure (pressure relative to atmospheric) of liquids and non-aggressive gases — water, water-glycol mixtures, refrigerants, and steam (up to 15 psi inlet). The pressure range is 0–100 psi, and the output is 4-20 mA active (4-20 mA current loop, immune to voltage drop on long cable runs).
Why a 4-20 mA output instead of 0-10V?
4-20 mA current loops are immune to voltage drop on long cable runs (useful when the sensor is more than ~150 ft from the BAS panel) and have built-in fault detection: 0 mA = broken loop, vs 0V on a voltage output which could mean either zero reading OR broken wiring. The trade-off is the 4-20 mA variant requires DC supply only (13.5-26.4 VDC); the 0-10V variants accept both AC and DC.
What is the burst pressure rating?
Burst pressure is 300 psi — 3× the high end of the measuring range. This protects the sensor from transient overpressure events common in hydronic systems: pump starts (water hammer), sudden valve closures, hydrostatic test events during commissioning, and chiller compressor cycling. The sensor will continue to read accurately at 200 psi (overpressure tolerance) — only physical damage occurs above the burst rating. Negative overpressure tolerance is -1 bar (-14.5 psi) to handle pump cavitation transients.
What media can I use this sensor with?
The stainless steel 1.4301 wetted parts and FKM (Viton-class) silicone-free seal are compatible with: water (hot, chilled, condenser), water-glycol mixtures (any concentration), refrigerants (R-410A, R-32, R-134a, R-1234ze, R-1234yf, and others), steam up to 100 kPa (15 psi) inlet pressure, and non-aggressive gases. NOT compatible with: chlorinated brine, ammonia (NH3 — corrodes copper and may damage stainless), aggressive industrial chemicals, or fluids above 255°F.
How is the sensor installed?
Thread the 1/4" NPT male connection into a standard hydronic tap or tee, using PTFE thread sealant or pipe dope rated for the fluid temperature. The MVS plug electrical connector (DIN EN 175301-803 Type A) lands on the back of the sensor housing — wire it with 0.5–1.5 mm¬≤ conductors. Mount in any orientation; the strain gauge is gravity-independent. For installations with significant vibration (near pumps), use a flexible pipe section or pulsation dampener upstream of the sensor.
What is the accuracy at typical HVAC operating temperatures?
Pressure accuracy varies with ambient temperature: <±0.5% FS at 70°F (21°C — the calibration reference), <±1.5% FS across the typical HVAC ambient range of 14-122°F (-10 to 50°C), and <±2% FS across the full operating envelope of -40 to 221°F. For a 100 psi range sensor, that's worst-case ±1.5 psi error in a normal mechanical room, ±2.0 psi at extreme ambient temperatures.
Where can I install this sensor — indoor or outdoor?
Indoor or outdoor — the stainless steel housing with IP65 / NEMA 4 rating handles wet, washdown, and outdoor environments. Operating ambient temperature range is -40 to 221°F. The most common applications are mechanical rooms (boiler/chiller plant), penthouse air-handler rooms, and rooftop hydronic loops. The fluid temperature range (-40 to 255°F) covers all standard HVAC heat-transfer fluids; frost protection is required below 36°F (2°C) on the fluid side to prevent freezing in the sensor cavity.
How is this different from other 22WP variants?
All 22WP variants share the same chassis (stainless steel housing, strain gauge on stainless steel membrane, 1/4" NPT connection, FKM seal). The differences are pressure range and output type. This SKU: 0–100 psi range with 4-20 mA active output. Same range with the alternate output: 22WP-516. Other ranges with 4-20 mA active output: 22WP-531 (Low); 22WP-534 (Medium); 22WP-537 (Very High).
Does it need 24V power?
Yes — 24 VDC only (13.5-26.4 VDC). 4-20 mA loop is current-driven so DC supply is required; AC will not power the loop correctly. Power consumption <0.6 W including the loop drive current.
- Sensor Type:
- Pressure / Liquid
- Sensing Element:
- Strain Gauge on Stainless Steel Membrane
- Output Signal:
- Pressure (single output)
- Output Style:
- Active Transmitter (mA)
- Output Type:
- 4-20 mA
- Power:
- 24 VDC only
- Number of Outputs:
- 1 analog
- Pressure Range:
- 0–100 psi
- Pressure Range Category:
- High
- Overpressure Tolerance:
- 200 psi
- Burst Pressure:
- 300 psi
- Pressure Accuracy:
- <±0.5% FS at 70°F
- Long-Term Stability:
- ±0.1% FS per year
- Pressure Connection:
- 1/4 NPT";Compatible Media=Water / Glycol / Refrigerants / Non-aggressive Gases"
- Housing Material:
- Stainless Steel 1.4301
- Seal Material:
- FKM (silicone-free)
- Mounting:
- Inline (1/4 NPT)";Enclosure=NEMA 4 / IP65"
- Display:
- No Display
- Supported Protocols:
- Analog only (no bus)
