BAPI BA/SW1A : Differential Pressure Switch (Plastic), Brown Spring Factory-Installed, 0.1-0.8 inWC (20-200 Pa) Adjustable Setpoint, SPDT Silver Contacts, 5A at 125 VAC, 6 Selectable Springs Included, 5-Year Warranty, Made in USA

What is the BA/SW1A used for?

The BA/SW1A is a BAPI differential pressure switch used in HVAC and Energy Management applications for air filter monitoring, static pressure proving, airflow proving, and auxiliary fan actuation. The SPDT silver contact closes (or opens) when the differential pressure across the diaphragm exceeds the configured trip point. Can sense positive pressure, vacuum, or true differential pressure depending on how the H and L ports are connected. This SKU ships with the Brown spring factory-installed for an initial range of 0.1-0.8 inWC (20-200 Pa).

How do I adjust the setpoint?

Insert a 0.110 inch (2.8 mm) square screwdriver bit (BA/SQ1BIT) into the pressure adjustment screw - accessed through a port in the front cover without opening the enclosure. Turn clockwise to increase the trip pressure, counterclockwise to decrease. With the Brown spring, each full turn represents approximately 0.4 inWC (100 Pa). The factory ships with the setpoint at 0.44 inWC (110 Pa) +/-10%. Make adjustments slowly - the built-in snubber orifice slows airflow into the diaphragm chamber, so the switch state can take a couple of seconds to settle after each adjustment.

Can I change to a different pressure range?

Yes - every BA/SW ships with all 6 range springs included. To change ranges: (1) Turn the pressure adjustment screw counterclockwise to remove it (careful not to drop). (2) Use a small wire hook (paper clip) to remove the current spring; place it in the plastic bag with the others. (3) Install the spring for the new range. (4) Replace the adjustment screw and turn clockwise slowly - between 3 and 6 turns the switch will close (low resistance), marking the low end of the new spring's working range. Use BAPI's setpoint table to dial in your final trip point. DO NOT OVERTIGHTEN - excess force damages the spring.

Which spring should I order?

This SKU ships with the Brown spring for 0.1-0.8 inWC. All 6 BA/SW SKUs share identical hardware; the only difference is the preinstalled spring (which determines the initial range out of the box). Pick the SKU whose range bracket includes your working set point - or order any SKU and swap to the appropriate spring after delivery, since all 6 are included with every unit. The 6 ranges and spring colors: Brown (0.1-0.8 inWC), Natural (0.5-1.2), Orange (0.7-2.2), Blue (3.2-10.4), Red (8.8-24), Purple (12-40). There is no SW4A; the family skips 4.

How do I wire the SPDT contact?

The SPDT silver contact has three quick-disconnect terminals inside the hinged cover: COM (common), NO (normally open), and NC (normally closed). Use 1/4 inch (6.4 mm) AMP-style crimp-on connectors (supplied with the unit). For prove flow (circuit closes when pressure rises - typical fan-status verification): wire COM and NO. For prove no flow (circuit opens when pressure rises - typical filter-clog alarm): wire COM and NC. Maximum load is 5A resistive at 125 VAC - the silver contact handles low-voltage signaling loads without oxidation issues. For higher loads (motor switching), use an interposing relay.

Which port is high and which is low?

The pressure ports are labeled H (high) and L (low) on the cover. Positive pressure only: connect to H; leave L open to atmosphere. Vacuum only: connect to L; leave H open to atmosphere. True differential: higher pressure to H, lower to L. For an air filter: upstream (cleaner air) to H, downstream (dirtier air) to L - the switch trips when the filter loads up and the differential exceeds the setpoint.

Can the BA/SW be used outdoors?

No - BAPI specifies the BA/SW is not intended for outdoor use. The enclosure is rugged plastic but is not IP54 or IP65 rated. For weather-exposed installations, use BAPI's BA/APSW Adjustable Pressure Switch series instead - the BA/APSW is available in both IP54 (-65 suffix for IP65) and offers a round dial-adjustable design with sealed cover. The BA/APSW also has a higher-current rating (1.5A at 250 VAC) if your load requires it.

What about the -PIB option I see in the datasheet?

The -PIB suffix is a BAPI special-order variant that relocates the H and L pressure ports from the hinged cover to the base of the enclosure - useful when you're using metal tubing (rigid copper or steel) and the cover-mounted ports would interfere with the tubing runs or prevent the cover from opening. Contact ZOT Supply to order a -PIB variant if your installation requires base-mounted ports.

What's the difference between BA/SW and BA/APSW?

BA/SW (this product family): rectangular hinged-cover plastic enclosure, 6 selectable springs included for field range changeover, 5A at 125 VAC, 1/4 inch barbed fittings, 1/4 inch quick-disconnect wiring, indoor-only. BA/APSW: round body with dial adjustment, IP54 or IP65 sealed (outdoor-capable), higher-current rating (1.5A at 250 VAC, 3A at 125 VAC), 1,000,000-cycle life, specified accuracy (+/-1 to +/-5%), and BAPI's optional total-tube accessory (BA/APSW-ACC) for in-duct mounting. Choose BA/SW for field-flexible range changes and distributor stocking; choose BA/APSW for outdoor-rated, higher-precision, or higher-current applications.

What's the warranty?

5-Year BAPI Limited Warranty - covers manufacturing defects in materials and workmanship under normal use. Manufactured in Gays Mills, Wisconsin, USA by Building Automation Products, Inc. ZOT Supply is an authorized BAPI distributor; warranty claims are processed directly with BAPI.