The Castair PSH1X is a 145-175 PSI pressure switch with built-in unloader valve, designed for piston air compressors that use a belt-drive pump. If your existing pressure switch has failed or you are building a compressor from major components, this is the replacement part. The PSH1X handles the high-pressure range — 145 PSI cut-in, 175 PSI cut-out — and includes the unloader valve that bleeds head pressure off the pump at shutdown. Without that unloader, the motor has to restart against full line pressure, which stalls single-phase motors and destroys start capacitors. This switch prevents that.
What This Switch Does
A pressure switch is the brain of a piston compressor. It monitors tank pressure, starts the motor when pressure drops to the cut-in point, shuts it off when pressure reaches cut-out, and tells the unloader valve to open so the pump starts unloaded on the next cycle. The PSH1X does all of this for the 145-175 PSI operating range.
Key Features
- Operating range: 145 PSI cut-in / 175 PSI cut-out — standard high-pressure range for shop compressors
- Unloader valve included: Bleeds residual head pressure after shutdown so motor restarts without load
- Corrosion resistant cover: Protects internal contacts from shop environment moisture and contaminants
- Easy to adjust: Differential and cut-out settings adjustable to fine-tune your operating range
- UL/CSA listed: Meets electrical safety standards for commercial shop use
- On/Off switch: Allows manual shutdown without pulling the plug
Pressure Switch Configuration Lineup
Castair offers pressure switches across two PSI ranges with multiple unloader and control configurations. Here is where the PSH1X fits:
- PSL1 — 95-125 PSI, no unloader
- PSL1X — 95-125 PSI, with unloader (same configuration as PSH1X, low-pressure range)
- PSL1MIX — 95-125 PSI, with unloader and on/off switch
- PSL4MIX — 95-125 PSI, with unloader, on/off, and four-way valve
- PSH1 — 145-175 PSI, no unloader
- PSH1X — 145-175 PSI, with unloader (this unit)
- PSH1MIX — 145-175 PSI, with unloader and on/off switch
- PSH4MIX — 145-175 PSI, with unloader, on/off, and four-way valve
- PSUV — Standalone unloader valve (add to an existing switch)
When Do You Need the PSH1X vs. Other Switches?
You need the PSH1X specifically when: your compressor runs in the 145-175 PSI range, it has a belt-drive single or two-stage pump, and the motor is single-phase (the unloader is critical on single-phase). If you are running a 95-125 PSI system, order the PSL1X instead — it is the same switch design, lower pressure range. If you need an on/off lever on the switch body, step up to the PSH1MIX. If your system has a four-port manifold setup, use the PSH4MIX.
The PSH1X is the most common high-pressure replacement switch for Castair compressors running single-phase motors. If your current switch has corroded contacts, a stuck unloader, or is chattering at cut-out, this is your direct replacement.
Technical Specifications
- Part Number: PSH1X
- Manufacturer: Castair (Cast Air)
- Pressure range: 145-175 PSI (cut-in 145 / cut-out 175)
- Unloader valve: Yes, included
- On/Off switch: No (see PSH1MIX for on/off)
- Certifications: UL/CSA listed
- Cover: Corrosion resistant
What's in the Box
- 1x Castair PSH1X pressure switch with integrated unloader valve
Why Buy From Air Compressor Factory Direct?
We are a specialist compressor parts supplier with real inventory of Castair components. When your compressor goes down, you need the right part fast — not a generic substitute. We stock the full Castair pressure switch lineup so you can get the exact configuration your system requires. Free shipping on qualifying orders. Call our tech line before you order if you are not sure which switch your compressor takes — we can help you confirm the right part number from your model information.
Call 866-217-0063 for quick answers and help\!
