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Low-pressure control / safety trips

What is going on

Possible causes and checks for: low-pressure control / safety trips.

Likely causes

  • Low charge, restriction, leak, evaporator freeze-up (safety control)
  • Or mis-set cut-out

Check in this order

  1. Cut-out ≈ sat. pressure at 10°F below target evap temp
  2. Cut-in ≈ highest allowable evap temp
  3. Safety setting below normal cut-out but above
  4. Psig
  5. Compare with table A30

More refrigeration guides

Related

Calculators and reference tables

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.