The Castair PSL1 is a 95-125 PSI pressure switch without an unloader valve. It handles the basic pressure control function — monitoring tank pressure, starting the motor at 95 PSI cut-in, and shutting it off at 125 PSI cut-out. There is no unloader valve on the PSL1. This switch is for compressor setups that have a separate unloader valve already installed, or for applications where the unloader function is handled elsewhere in the system. If your pump does not already have a separate unloader and you are running a single-phase motor, you likely need the PSL1X instead.
What This Switch Does (and Does Not Do)
A pressure switch without an unloader is simpler but requires more care in application. When the motor shuts off, the pump stops against whatever pressure is in the discharge line. On the next start cycle, the motor has to push against that residual pressure to get the pump moving again. On small motors and compressors designed for this (oil-less pancake units, some DC units), this is acceptable. On larger belt-drive single-phase units, starting against head pressure kills start capacitors and trips thermal overloads. Know your application before ordering the PSL1.
Key Features
- Operating range: 95 PSI cut-in / 125 PSI cut-out — standard low-pressure shop range
- No unloader valve: For systems with existing separate unloader or applications that do not require one
- Corrosion resistant cover: Protects contacts from shop moisture and debris
- Easy to adjust: Cut-out and differential settings field-adjustable
- UL/CSA listed: Meets commercial electrical safety standards
Full Castair Pressure Switch Lineup — 95-125 PSI Range
- PSL1 — 95-125 PSI, no unloader (this unit, $36.31)
- PSL1X — 95-125 PSI, with unloader ($39.85)
- PSL1MIX — 95-125 PSI, with unloader and on/off lever ($40.73)
- PSL4MIX — 95-125 PSI, with unloader, on/off lever, and four-way valve
When Does a Shop Need the PSL1?
The PSL1 fits these specific scenarios: you already have a separate external unloader valve plumbed into the system, you are replacing a switch on a compressor that was factory-built without an integral unloader, or you are building a custom system where the unloader function is handled by a separate component such as the Castair PSUV. If you are unsure whether your compressor has a built-in unloader, look at the pump head — if there is a small valve with a copper or brass tube running from it back to the intake, you have an unloader and can use the PSL1. If there is no such valve, you need the PSL1X.
Technical Specifications
- Part Number: PSL1
- Manufacturer: Castair (Cast Air)
- Pressure range: 95-125 PSI
- Unloader valve: No
- On/Off switch: No
- Certifications: UL/CSA listed
- Cover: Corrosion resistant
- Price: $36.31
What's in the Box
- 1x Castair PSL1 pressure switch (no unloader valve)
Why Buy From Air Compressor Factory Direct?
We carry the full Castair pressure switch lineup so you can get the right configuration without substituting. If you are not certain whether the PSL1 or PSL1X is correct for your system, call before ordering — we can walk you through identifying what your compressor needs. Free shipping on qualifying orders.
Call 866-217-0063 for quick answers and help!
