The 22WDP-512 is a Belimo active 24V differential pressure sensor for liquids - designed for differential pressure measurement on water, water-glycol mixtures, and steam (up to 15 psi inlet) in HVAC hydronic systems. The sensor covers a Low-Medium (0-30 psi) measuring range with 0-10V active output. Two pressure ports (+ high-side and - low-side, both 1/4" NPT) connect across the device being monitored - a pump, heat exchanger, balance valve, coil, or filter - and the sensor outputs the pressure differential as a linear analog signal. The sensing element uses a stainless steel and ceramic diaphragm with +/-1% of measuring range accuracy across a 23-167 degF operating envelope. The housing combines a stainless steel 1.4305 bottom (wetted side) with a die-cast aluminum top cover, sealed with EPDM gaskets - rated NEMA 4 / IP65 for mechanical-room and washdown environments. Burst pressure is 300 psi (common across all four range variants), with -1 bar negative overpressure tolerance to survive pump cavitation transients. Mounting orientation is unrestricted - install vertical, horizontal, or any angle.
Differential pressure monitoring on liquid HVAC systems where the expected pressure drop falls in the 0-30 psi range: air-handler coil pressure drop, fan-coil and reheat coil monitoring, low-static building hydronic loops, zone valve monitoring. For the same range with 4-20 mA output instead (useful for long cable runs or controllers preferring current loops), see 22WDP-532. Same output style, other ranges: 22WDP-511 (Low (0-15 psi)), 22WDP-514 (Medium (0-50 psi)). For single-port (gauge) pressure measurement instead of differential, see the 22WP family - same hydronic platform but measures gauge pressure with a single 1/4" NPT port.
Key Features
Strain-gauge diaphragm sized for the 0-30 psi differential envelope - matched to typical commercial hydronic pump head, heat exchanger pressure drop, and balancing applications. +/-1% of measuring range accuracy with 300 psi burst pressure for water-hammer protection.
Two 1/4" NPT pressure ports (+ high-side, - low-side) measure the pressure differential across a device - pump, heat exchanger, balance valve, coil, or filter. Output is a linear analog signal proportional to the differential pressure. Unrestricted mounting orientation (vertical, horizontal, or any angle).
Stainless steel 1.4301 housing with ceramic-based diaphragm - chemically compatible with water, water-glycol mixtures, and steam (up to 15 psi inlet). The stainless/ceramic wetted parts resist corrosion in long-term hydronic service where mild steel or brass alternatives would scale or corrode.
Accuracy spec is +/-1% of measuring range across the 23-167 degF (-5 to 75 degC) operating envelope - applies uniformly across the full operating temperature range rather than degrading at the extremes. Long-term stability +/-2.5% per 10 years - calibration-free for the decade-plus service life typical of HVAC sensors.
Burst pressure of 300 psi - significantly above the measuring range and overpressure tolerance - survives transient overpressure from pump starts (water hammer), sudden valve closures, hydrostatic test events, and chiller compressor cycling. The constant 300 psi burst rating across all range variants means low-range SKUs (0-15 / 0-30 psi) have proportionally more headroom than would be typical for a single-port pressure sensor.
Stainless steel 1.4305 bottom (wetted side) with die-cast aluminum top cover, sealed with EPDM gaskets - NEMA 4 / IP65 rated for wet, washdown, and mechanical-room environments. Operating ambient 14-122 degF (-10 to 50 degC); fluid temperature 15-175 degF (-10 to 80 degC) with frost protection required below 36 degF.
Standard angle plug connector per DIN 43650 construction A - robust, field-serviceable, and accepts 0.5-1.5 mm2 wire. The 90 deg orientation lets cable exit either side of the sensor for tight mounting clearances near pumps and valves.
Industry-leading factory warranty backed by Belimo's worldwide service network.
Technical Specifications
| Specification | Detail |
|---|---|
| Sensor Style | Active differential pressure sensor for liquids |
| Measured Value | Differential pressure (high port - low port) |
| Measuring Fluid | Water, water-glycol mixtures, steam (<=100 kPa / 15 psi inlet), non-aggressive gases |
| Sensing Diaphragm | Stainless steel 1.4301 with ceramic element |
| Output Signal | 1x active analog: 0-10 V, min. 2 kOhm load resistance |
| Pressure Measuring Range | 0-30 psi differential |
| Overpressure Tolerance (Positive) | 85 psi |
| Overpressure Tolerance (Negative) | -1 bar (-14.5 psi) - handles pump cavitation transients |
| Burst Pressure | 300 psi (common across all 22WDP range variants) |
| Pressure Accuracy | +/-1% of measuring range across 23-167 degF (-5 to 75 degC) |
| Long-Term Stability | +/-2.5% per 10 years |
| Typical Response Time | 100 ms |
| Power Supply | AC/DC 24V (AC 21.6-26.4V / DC 13.5-26.4V); 0.9 VA AC / 0.37 W DC |
| Power Consumption | 0.9 VA AC / 0.37 W DC |
| Electrical Connection | Angle plug per DIN 43650 construction A, accepts 0.5-1.5 mm2 wire |
| Pressure Connection | 2x 1/4" NPT (high-side + / low-side -) |
| Mounting | Unrestricted orientation - install vertical, horizontal, or any angle |
| Housing - Bottom (wetted side) | Stainless steel 1.4305 |
| Housing - Top Cover | Die-cast aluminum |
| Housing Seal | EPDM gasket |
| Wetted Parts | Stainless steel 1.4301 and ceramic |
| Enclosure Rating | NEMA 4 / IP65 (wet/washdown environments) |
| Protection Class | IEC/EN III, PELV (Protective Extra-Low Voltage) |
| Power Source UL | Class 2 Supply |
| Ambient Temperature | 14 to 122 degF (-10 to 50 degC) |
| Fluid Temperature | 15 to 175 degF (-10 to 80 degC) - frost protection required below 36 degF (2 degC) |
| 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 | 22WDP-512 |
| Warranty | 5-year factory warranty |
What's In the Box
- 22WDP-512 liquid differential pressure sensor with stainless steel bottom + die-cast aluminum top cover
- Angle plug electrical connector (DIN 43650 construction A)
Note: thread sealant (PTFE tape or pipe dope rated for the working fluid temperature) is NOT included. Pipe connection adapters (stainless steel or brass 1/4" NPT) are available as optional accessories - useful for installations where the existing piping has different tap thread sizes or where the installer prefers isolation valves on the sensor lines.
Documentation
Frequently Asked Questions
What does the 22WDP-512 measure?
It measures the differential pressure between two points in a hydronic system - the pressure at the + port minus the pressure at the - port. The range is 0-30 psi differential, and the output is 0-10V active. Typical applications: pump head (across pump suction/discharge), heat exchanger pressure drop (across primary and secondary sides), balance valve setpoint verification, coil pressure drop monitoring.
How do I install a differential pressure sensor?
Tap two 1/4" NPT connections on the piping you're measuring across - one upstream (high pressure side, connects to + port) and one downstream (low pressure side, connects to - port). Use installer-supplied PTFE thread sealant or pipe dope. Connect the two ports to the sensor's + and - ports with rigid or flexible tubing. For pump head measurement, the + port goes to the discharge side, - port to suction. The sensor mounting orientation is unrestricted - install whatever way fits the mechanical room space. We recommend isolation valves on both tubing lines so the sensor can be serviced or replaced without draining the loop.
What media can I use this sensor with?
Designed for water, water-glycol mixtures (any concentration), and steam (inlet up to 15 psi). The stainless steel 1.4301 + ceramic wetted parts handle hot water, chilled water, and condenser water in long-term service. Compatible with non-aggressive gases. NOT designed for refrigerants like the single-port 22WP - the EPDM seals and ceramic diaphragm aren't qualified for refrigerant exposure, and the narrower fluid temperature range (15-175 degF vs 22WP's -40 to 255 degF) is incompatible with refrigerant high-side pressures.
What is the burst pressure rating and why is it constant across all ranges?
Burst pressure is 300 psi for all four 22WDP range variants (0-15, 0-30, 0-50, 0-100 psi). This is intentional: the ceramic diaphragm has fixed mechanical tolerance regardless of the strain-gauge calibration range. The result is that lower-range variants (0-15 / 0-30 psi) have proportionally MORE burst headroom (20x and 10x the nominal range) than higher-range variants (3x on the 0-100 psi). All variants comfortably survive transient overpressure from pump starts, sudden valve closures, and water hammer. Negative overpressure tolerance is -1 bar (-14.5 psi) to handle pump cavitation transients.
How is this different from the 22WP single-port pressure sensor?
22WP measures gauge pressure (single port - pressure vs atmosphere) at one point in a hydronic system. 22WDP (this SKU) measures differential pressure (two ports) across a device - pump, heat exchanger, valve, coil. Both share the stainless steel construction and strain-gauge sensing but the 22WP has a wider operating envelope (-40 to 221 degF vs 14-122 degF ambient) and supports refrigerants and broader fluid types because of its FKM seals; the 22WDP uses EPDM seals and ceramic diaphragm specifically optimized for water/glycol service. Choose 22WDP when you need pump head, balance, or pressure drop measurement; choose 22WP for boiler/chiller plant pressure, expansion tank, or refrigerant pressure monitoring.
Why is the response time 100 ms instead of faster?
The 100 ms typical response time is intentionally damped for differential pressure applications. Pump head and balance-valve differential pressures have inherent noise from pump pulsation, valve modulation, and hydronic transient events - a faster sensor would output noisy readings that the BAS would have to filter anyway. The 100 ms response is fast enough to track real load changes (pump speed changes, balance valve adjustments) but slow enough to ignore pulsation noise. For applications needing faster response (gauge pressure trending, expansion-tank monitoring), the single-port 22WP at 2 ms response time is the right choice.
Where can I install this sensor?
Indoor mechanical rooms, penthouse air-handler rooms, hydronic pump skids. NEMA 4 / IP65 rated for wet and washdown environments. Operating ambient 14-122 degF (-10 to 50 degC) - narrower than the 22WP single-port (-40 to 221 degF) because the die-cast aluminum top cover has tighter thermal constraints. Fluid temperature 15-175 degF (-10 to 80 degC) - covers standard hot water and chilled water but not refrigerants or very hot process fluids. Mounting orientation is unrestricted.
Does it need 24V power?
Yes - 24 VAC or 24 VDC supported (AC 21.6-26.4V / DC 13.5-26.4V). Power consumption 0.9 VA AC / 0.37 W DC - compatible with standard 24V control transformers shared with actuators and other sensors.
Are accessories available for the pressure connection?
Yes. Stainless steel and brass 1/4" NPT pipe connection adapters are available as optional accessories - useful for installations where the existing piping has different tap thread sizes or where the installer prefers isolation valves on the sensor lines. Belimo also offers pre-made 3-valve manifolds for the sensor ports (allows zero-checking the sensor by equalizing both sides without draining the loop) - particularly useful for low-range variants (0-15 psi) where zero drift becomes a significant percentage of the reading.
- Brand:
- Belimo
- Series:
- 22WDP
- Pressure Range Category:
- Low (up to 30 psi)
- Output Signal:
- 0-10V
- Hazardous Location:
- Standard
- Display:
- No Display
- Enclosure:
- NEMA 4 / IP65
- Bypass Manifold:
- None
- Cable Type:
- M12 Connector
- Power Supply:
- 24 VAC/VDC
- Wetted Material:
- Stainless Steel + Ceramic
- Country of Origin:
- Switzerland
