The ACI PT 7.5" is a plastic differential-velocity pitot tube designed for VAV (Variable Air Volume) boxes and other small-duct HVAC applications. Unlike single-port static or velocity probes, the PT series features both high (H) and low (L) pressure sensing ports in a single duct-mounted unit — allowing direct differential pressure measurement (and therefore velocity / flow calculation) with a single probe and a single duct penetration.
The PT 7.5" has a 7.5 in (19.1 cm) insertion length with 3 sensing point sets averaging along the probe shaft — sized for 8 to 10 in duct diameter applications. Multiple sensing points produce a more representative velocity reading than a single-point probe (averaging out flow profile irregularities). Mount with the arrow on the probe facing in the direction of air flow; place at least 10 straight duct diameters upstream and downstream of any elbows or reducers for best results. A foam pad on the mounting plate seals the installation opening and reduces vibration-induced noise.
VAV box flow measurement in 8 to 10 in diameter ducts, branch line air flow monitoring, terminal unit flow verification, and any small-duct HVAC application requiring true differential velocity measurement from a single probe. Air flow range 200 to 3000 FPM. 3 sensing point sets provide averaged velocity sampling along the probe shaft.
Key Features
Both H (high) and L (low) pressure ports are integrated into the single duct-mounted probe — allowing direct differential velocity pressure measurement from a single probe and a single duct penetration. No separate static reference tap required.
The PT 7.5" has 3 sensing point sets averaging along the 7.5 in probe shaft — 3 sets provide averaged velocity sampling across the duct cross-section for a more representative reading than single-point probes.
Recommended for ducts in the 8 to 10 in diameter range. For smaller or larger ducts, see the alternate PT-series sizes (PT 3 in, 5.2 in, 7.5 in, or 9.7 in) for the correct insertion length per duct diameter.
ABS housing rated UL-94 HB. Adhesive foam pad on the mounting plate seals the installation opening and damps vibration-induced noise — both critical for low-DP velocity measurement accuracy. Mount with the flow arrow on the probe pointing in the direction of air flow.
Recommended air flow range 200 to 3000 FPM covers the working envelope of most VAV terminal boxes and small-duct branch lines. Operating temperature 40 to 120 deg F (4 to 49 deg C). RoHS2, WEEE, and REACH compliant.
Technical Specifications
| Specification | Value |
|---|---|
| SKU | PT 7.5" |
| Series | PT Plastic VAV Pitot Tube |
| Probe Type | Differential Velocity (H/L ports integrated) |
| Tubing Connection | 3/16 in OD (4.8 mm) connection for 1/4 in (6.4 mm) OD poly tubing |
| Sensing Insertion Length | 7.5 in (19.1 cm) |
| Number of Sensing Point Sets | 3 sets |
| Recommended Duct Size | 8 to 10 in (20.3 to 25.4 cm) |
| Recommended Air Flow | 200 FPM (60.96 MPM) minimum to 3000 FPM (914.4 MPM) maximum |
| Operating Temperature Range | 40 to 120 deg F (4 to 49 deg C) |
| Storage Temperature Range | -40 to 185 deg F (-40 to 85 deg C) |
| Operating Humidity | 0 to 90% RH non-condensing |
| Material Type | ABS |
| Material Flammability Rating | UL-94 HB |
| Mounting Plate Width | 4.00 in (10.2 cm) |
| Mounting Plate Height | 2.1 in (5.3 cm) |
| Overall Length | 21.1 cm |
| Weight | 0.075 lb (0.034 kg) |
| Duct Penetration | 7/8 in (22.2 mm) hole |
| Mounting Hole Spacing | 3.3 in (8.38 cm) center-to-center, 3/16 in (4.76 mm) holes |
| Mounting Fasteners | (2) sheet metal screws or rivets (not included) |
| Agency Approvals | RoHS2, WEEE, REACH |
| Warranty | 2-year ACI Limited Warranty (PT Series) |
What’s In the Box
- ACI PT 7.5" Plastic VAV Pitot Tube (7.5 in insertion length, 3 sensing sets)
- Pre-installed foam mounting gasket
- Installation instructions (also available below as PDF)
Recommended Companion Products
The PT 7.5" uses 1/4 in OD poly tubing for both H and L port connections. ACI medical-grade tubing kits in four lengths:
Other ACI PT plastic VAV pitot tubes sized for different duct diameters:
Documentation
Frequently Asked Questions
The PT 7.5" is a plastic differential-velocity pitot tube with both H (high) and L (low) pressure ports integrated into a single duct-mounted probe. Unlike the SPT (static only) or VPT (velocity only) aluminum probes, which require a separate static reference for velocity calculation, the PT measures velocity pressure differential directly from a single duct penetration. It's specifically designed for VAV boxes and small-duct applications — the PT 7.5" suits ducts from 8 to 10 in diameter.
Match the probe insertion length to the duct diameter so the sensing points span across the duct cross-section for representative averaging. Recommended pairings: PT 3 in for 4-6 in ducts (1 sensing set), PT 5.2 in for 6-8 in ducts (2 sets), PT 7.5 in for 8-10 in ducts (3 sets), PT 9.7 in for 10-18 in ducts (4 sets). Pick based on the actual duct diameter at the installation point; using a probe sized for a smaller duct in a larger duct leaves the sensing points off-center and reduces averaging accuracy.
The PT 7.5" has 3 sensing point sets distributed along the probe shaft. Multiple sensing sets (3 on this variant) average the velocity reading across the duct cross-section — reducing error from non-uniform flow profiles (common in real-world ducts with limited straight-pipe run upstream). More sets generally give more accurate velocity readings, especially in larger ducts.
Drill a 7/8 in hole in the duct, plus two 3/16 in holes spaced 3.3 in center-to-center (use the drill template in the install PDF). Insert the probe into the duct with the flow arrow pointing in the direction of air flow. The foam gasket on the mounting plate seals the installation opening and damps vibration. Fasten the flange to the duct using two sheet metal screws or rivets (not included) inserted through the 3/16 in mounting holes. Connect 1/4 in OD poly tubing to the H and L ports.
Yes — per the install manual, if you only need static pressure (filter status or fan operation, not velocity), use only the H port connection and rotate the probe 90 degrees so the sensing point opens parallel to the air stream. This converts the PT into an effective static probe. For dedicated static-only applications, however, the ACI SPT aluminum static probes (SPT-3.5" or SPT-8.0") are a better fit at lower cost.
Any low-DP differential pressure transmitter that accepts 1/4 in OD poly tubing on both the high and low ports — including ACI's own DLP and MLP2 series, BAPI ZPM zone pressure multi-sensors, Dwyer's 600- and 700-series differential transmitters, Senva pressure transmitters, and most other low-DP air pressure transmitters. For velocity / flow calculation, the transmitter must support velocity-pressure-to-FPM conversion (most modern BAS-compatible transmitters do).
