Refrigeration Pressure Switch Guide: Understanding PSI Open/Close Ratings

Refrigeration pressure switches protect compressors from operating outside their safe range — but with low-pressure (LP) and high-pressure (HP) switches available across dozens of PSI settings, picking the correct one means understanding exactly what "open" and "close" ratings mean.

Open vs. Close: What These Ratings Actually Mean

A fixed-setting pressure switch has two key numbers:

  • Opens at X PSI — the pressure at which the switch breaks the circuit, shutting down the compressor to protect it
  • Closes at Y PSI — the pressure at which the switch remakes the circuit, allowing the compressor to run again

On a low-pressure switch, the compressor shuts off when pressure drops too low (risk of coil icing or lubrication loss) and restarts once pressure recovers. On a high-pressure switch, the logic flips: the compressor shuts off when pressure climbs too high (risk of a ruptured line or damaged compressor) and won't restart until pressure drops to a safe level.

Low-Pressure (SLP) Switch Ratings

Model Opens Closes Proof / Burst
SLP05-20 5 PSI 20 PSI 250 / 5000
SLP10-25 10 PSI 25 PSI 250 / 5000
SLP25-50 25 PSI 50 PSI 250 / 5000

The full SLP line runs from SLP05-20 up through SLP90-120, covering low-pressure cutout points from 5 PSI to 90 PSI.

High-Pressure (SHP) Switch Ratings

Model Opens Closes Proof / Burst
SHP200-150 200 PSI 150 PSI 500 / 5000
SHP250-150 250 PSI 150 PSI 500 / 5000

The full SHP line runs from SHP200-150 up through SHP610-460, covering high-pressure cutout points up to 610 PSI — the higher end needed for R410A and other higher-pressure refrigerants.

⚠ Never Guess on Rating Installing a pressure switch rated for the wrong refrigerant or system type can mean the compressor either short-cycles constantly or never trips a protective cutout at all. Always match the switch to the manufacturer's specified opening and closing pressure — not just "close enough."

Fan Cycling & Manual Reset Switches

Beyond fixed LP/HP switches, fan cycling switches (SPF series) turn the condenser fan on and off based on head pressure to help systems perform in low ambient conditions, while manual reset switches (SPM series) require a technician to physically reset the switch after a high-pressure trip — a deliberate safety design so the system isn't automatically restarted after a serious fault.

💡 Pro Tip A compressor that trips a high-pressure switch repeatedly is rarely a switch problem — check for a dirty condenser coil, failed condenser fan motor, overcharge, or non-condensables in the system before replacing the switch itself.

Quick Answers

What's the difference between "proof" and "burst" pressure?

Proof pressure is the maximum pressure the switch can be exposed to without damage while still functioning normally. Burst pressure is the pressure at which the switch housing itself could fail — a safety margin, not an operating spec.

Can I use an LP switch as a substitute HP switch?

No. LP and HP switches trip in opposite directions relative to pressure and are not interchangeable in function, even if the physical fitting matches.

Why Wholesalers Stock Smart Electric®

Every pressure switch in the line is clearly labeled with its open/close ratings and proof/burst specs, so your counter staff and contractor customers can match the correct part quickly:

  • Sold exclusively through HVACR wholesalers — never big-box retail
  • Full LP and HP coverage across dozens of PSI settings
  • Packaging built for accurate, fast identification at the counter

Talk to a Smart Electric® Rep →

Back to blog