ACI A/WPR2-300-M10-LCD : Wet/Wet Diff Pressure, LCD, 4 Sub-Ranges Uni/Bi (0-300 psid), V/mA Selectable, 304L SS Sensors, 10-ft Metal-Clad Cable, NEMA 4X/IP66, 5-Yr, Made in USA

What does the A/WPR2-300-M10-LCD measure and output?

It measures the differential pressure between two physically separated tap points - the high-side transducer reading minus the low-side transducer reading. The maximum line pressure envelope is 300 psi, with 4 DIP-selectable uni-directional sub-ranges (0-300, 0-150, 0-75, 0-30 psid) and 4 bi-directional sub-ranges (+/-300, +/-150, +/-75, +/-30 psid). Output is one active analog signal: 0-5 VDC, 0-10 VDC, or 4-20 mA, switch-selectable on the same SKU.

When do I use bi-directional mode instead of uni-directional?

Uni-directional (factory default) is correct for the vast majority of HVAC applications - pumps and pressure-drop monitoring where the high side is always at higher pressure than the low side. Bi-directional is required when the flow direction can reverse - reversible-flow heat recovery loops, dual-pump systems with auto-changeover, or balance work where the operating sense flips between modes. In bi-directional mode, 0 inWC produces a mid-scale output (12 mA, 2.5 V, or 5 V). Switching modes requires power off and DIP switch SW7 position 1 reconfiguration.

How does the universal output (V or mA) work?

An on-board DIP switch (SW8 for output type, SW7 position 2 for output mode) selects between 0-5 VDC, 0-10 VDC, or 4-20 mA. Factory default is 0-10 VDC. To change: power off the unit, open the housing, flip the appropriate DIP switch, close, and power on. The new mode takes effect on power-up only. Use 4-20 mA for cable runs over ~150 ft or in electrically noisy environments; voltage outputs are simpler for short runs.

Should I size by differential pressure or by max line pressure?

Always size by max line pressure, not by differential pressure. The max line pressure is the absolute pressure at the high-side transducer (relative to atmosphere) - the sensor must withstand this at its + port even if the differential between + and - is much smaller. The A/WPR2-300-M10-LCD is rated for 300 psi max line pressure, with proof pressure of 600 psi and burst pressure of 3000 psi. If your maximum line pressure exceeds 300 psi, step up to the next family member.

When and how should I auto-zero the unit?

Auto-zero on initial installation and any time the unit reads a non-zero differential when both sensors are at equal pressure (e.g., both open to atmosphere with main pressure shut off). Procedure: (1) Shut off main pressure and equalize both lines to atmosphere via drain valves. (2) Wait at least 15 minutes for warm-up. (3) Press and hold the internal AUTO ZERO button (or short the remote ZERO terminal to COM) for 2 seconds. On LCD units, the 'ZERO' icon will illuminate during zeroing and flash twice when complete. Then re-pressurize and verify reading.

What does the LCD show?

The on-housing LCD has 2 lines x 8 characters. During normal operation it shows the HIGH pressure, LOW pressure, and differential pressure values in the selected units (PSI by default, switchable to BAR via DIP switch SW3 position 3). Special indicators: 'ZERO' while auto-zero is in process, 'OVR' when either input exceeds the max line pressure, and 'ERROR' when the differential is out of the selected range. On boot, the unit briefly displays the software version, pressure range, and output type.

Why metal-clad cable vs standard PVC?

The metal-clad option uses a continuously interlocked Type 304 stainless steel core around the cable harness - protecting against abrasions, cuts, and corrosion in harsh mechanical room environments, on vibrating equipment skids, or in areas with high foot/equipment traffic. Specify metal-clad when local code requires armored cabling, or when the cable run passes through high-abuse areas. For typical above-ceiling routing in commercial buildings, the standard CMP PVC variant is appropriate and significantly less expensive.

What media can this sensor handle?

Any liquids, gases, or refrigerants compatible with 304L (or 316L) stainless steel and a Neoprene seal. Typical HVAC applications: water, water-glycol mixtures, refrigerants (R-410A, R-134a, etc.), light oils, compressed air, and non-aggressive gases. NOT suitable for ammonia, chlorinated brines, strong acids/bases, or seawater - these can attack the stainless steel or Neoprene seal. Fluid temperature at the transducer must stay between -40 and 257 deg F; use a pigtail siphon to lower steam or hot-water temperature if needed.

What's the power requirement?

Voltage output mode: 16-36 VDC or 24 VAC +/-10% at 50/60 Hz. Current (4-20 mA) output mode: 18-36 VDC (with 250 ohm load) or 20-36 VDC (with 500 ohm load), or 24 VAC. Supply current is 24 mA minimum for current output, 6 mA minimum for voltage output. Compatible with standard 24V control transformers shared with actuators and other sensors - ACI recommends an isolated UL Class 2 transformer when using 24 VAC, and snubber diodes/MOVs on any shared inductive loads to prevent voltage spikes.

How does the WPR2 compare to Belimo's 22PDP?

Both are wall-mount remote wet-to-wet differential pressure transmitters with selectable output and sub-ranges. WPR2 advantages: uni-directional AND bi-directional modes (8 total sub-ranges vs Belimo's 4 uni-only), Made in USA, available with metal-clad armored cable. Belimo 22PDP advantages: cULus listed (WPR2 is CE only - specify Belimo when code requires UL), higher burst pressure on the lower-range model (Belimo 22PDP-585 = 2000 psi vs WPR2-100 = 1000 psi), and a fluid temperature rating up to 220 deg F at the transducer. Choose WPR2 for bi-directional or Made-in-USA applications, and Belimo 22PDP when UL listing is required by spec or code.

Is the WPR2 UL or cULus listed?

No - the ACI WPR2 is approved under CE, RoHS2, WEEE, and REACH, but is not cULus listed. If your specification or local code requires UL/cULus listing on the pressure sensor itself, choose the Belimo 22PDP family (cULus listed per UL 60730-1/-2-6) from the same subcategory. For projects without a UL listing requirement, the WPR2 is fully compliant under the listed approvals.