Schneider Electric 9038CR34 Class 9012 Pressure Switch

The Schneider 9038CR34 is a diaphragm‑actuated pressure switch from the Class 9012 series. It is designed for controlling pumps, compressors, and other fluid handling equipment based on system pressure. The switch features a single‑pole double‑throw (SPDT) snap action contact with a fixed differential. The adjustable pressure range is 1–15 psi (0.07–1.03 bar), making it suitable for low‑pressure applications such as water pressure control, air compressors, and booster pump systems. The unit is housed in a NEMA 1 (general purpose) enclosure and is equipped with a diaphragm sensing element compatible with water, air, and non‑corrosive fluids.

Technical Specifications

Functional Description

The 9038CR34 uses a flexible diaphragm to sense the applied fluid pressure. When the pressure rises above the setpoint, the snap‑action mechanism instantly transfers the common terminal contact from NC to NO, opening the control circuit. When the pressure falls below the setpoint minus the fixed differential, the contact returns to its normally closed position. This hysteresis prevents rapid cycling (chattering) of the controlled equipment. The setpoint is adjusted via a calibrated spring inside the switch, accessible by removing the enclosure cover. The switch is supplied with a 1/4” NPT female pressure port, allowing direct connection to a pipe or manifold.

Installation and Wiring

Mount the switch vertically on a rigid surface using the two slotted mounting holes (keyhole style). The pressure port should be connected to the system using a suitable pipe sealant. Do not overtighten. Wiring is made to the three screw terminals: COM (common), NO (normally open), and NC (normally closed). For pump control, typical wiring uses the NO contact to start the pump when pressure drops and the NC contact to stop when pressure reaches setpoint. Use copper wire only, 14 AWG to 18 AWG. Tightening torque: 5–7 in‑lb (0.56–0.79 Nm). Ensure the enclosure cover is securely closed after adjustments.

Adjustment Procedure

To set the cut‑in pressure, connect a pressure gauge to the system and adjust the large spring (range screw) while the system is running. Turn clockwise to increase the cut‑in pressure, counter‑clockwise to decrease. The cut‑out pressure will be the cut‑in pressure plus the fixed differential. The differential is factory set and cannot be changed. For applications requiring adjustable differential, a different model (e.g., 9038DR34) should be selected.

Applications

The 9038CR34 is used in residential and commercial water pressure booster pumps, small air compressors (tank mounted), irrigation control systems, industrial coolant pumps, and low‑pressure alarm circuits. Its NEMA 1 enclosure is suitable for dry indoor locations.

Maintenance and Safety

Inspect the switch annually for signs of leakage or corrosion. The diaphragm material is nitrile rubber (Buna‑N), compatible with water, air, light oils, and many non‑aggressive fluids. It is not suitable for gasoline, solvents, or strong acids. If the switch fails to trip, clean the contacts with a contact burnisher. The electrical contacts are not user‑replaceable; replace the entire switch if contacts are welded or severely pitted.

Conclusion

The Schneider 9038CR34 pressure switch provides reliable, low‑pressure control for fluid and air systems with a simple SPDT snap action design, backed by Schneider Electric’s robust manufacturing standards.