The Castair PSH4MIX is the full-featured version of the 145-175 PSI pressure switch lineup. It includes a built-in unloader valve, an on/off lever for manual control, and a four-way valve port configuration. This is the switch you need when your compressor system requires independent control of multiple circuits from a single pressure switch, or when the pump manifold has a four-port connection. If you are just replacing a failed switch on a standard two-port setup, look at the PSH1X or PSH1MIX first — the PSH4MIX is for systems specifically plumbed for four-way operation.
What the Four-Way Configuration Means
A standard pressure switch has one unloader port. The four-way version adds additional ports for systems that route unloader air to multiple pump heads, duplex compressor setups, or specialized manifold configurations. On duplex units running two pumps from a shared tank, the four-way valve allows both pump heads to unload simultaneously from one switch. This keeps head pressure off both cylinders at shutdown and ensures clean motor restarts on both units.
Key Features
- Operating range: 145 PSI cut-in / 175 PSI cut-out — high-pressure shop range
- Unloader valve: Included — bleeds head pressure at shutdown for unloaded motor restarts
- On/Off switch: Manual lever on switch body for controlled shutdown without cutting power at the panel
- Four-way valve configuration: Multiple unloader ports for duplex or multi-head pump systems
- Corrosion resistant cover: Protects electrical contacts in shop environments
- Easy to adjust: Cut-out and differential adjustable without special tools
- UL/CSA listed: Meets commercial electrical safety standards
Full Castair Pressure Switch Lineup — 145-175 PSI Range
Castair builds four variants at 145-175 PSI. Choose based on what your system actually requires:
- PSH1 — 145-175 PSI, no unloader (use only on compressors with separate unloader)
- PSH1X — 145-175 PSI, with unloader (most common single-phase replacement)
- PSH1MIX — 145-175 PSI, with unloader and on/off lever
- PSH4MIX — 145-175 PSI, with unloader, on/off, and four-way valve (this unit)
95-125 PSI Equivalent
- PSL4MIX — 95-125 PSI version of this switch with the same four-way, on/off, and unloader configuration
When Do You Need the PSH4MIX?
Order the PSH4MIX when your compressor has a four-port manifold connection on the pump head or when you are running a duplex setup where two pump heads share one pressure switch. If your system only has a single unloader port, the PSH1X or PSH1MIX is the right call — you do not need the four-way ports. If your existing switch has an on/off lever and multiple unloader ports at 145-175 PSI, the PSH4MIX is your direct replacement.
Technical Specifications
- Part Number: PSH4MIX
- Manufacturer: Castair (Cast Air)
- Pressure range: 145-175 PSI
- Unloader valve: Yes, included
- On/Off switch: Yes, manual lever
- Valve configuration: Four-way
- Certifications: UL/CSA listed
- Cover: Corrosion resistant
What's in the Box
- 1x Castair PSH4MIX pressure switch with integrated unloader valve, on/off lever, and four-way valve ports
Why Buy From Air Compressor Factory Direct?
We stock the complete Castair pressure switch lineup — not just the common single-port models but the specialty four-way configurations as well. If you are not certain whether your system needs the PSH4MIX or a simpler variant, call us before ordering. We can help you identify the right switch from your compressor model number. Free shipping on qualifying orders. Full manufacturer support.
Call 866-217-0063 for quick answers and help!
