Rivacold LP

What does Rivacold LP mean?

On the Carel controllers fitted to Rivacold plug-in units, LP is the low evaporation pressure alarm: when the evaporation pressure falls below the configured threshold (LPt) for the set time, the controller stops the unit and shows LP on the display. The alarm delay is differentiated between steady operation (LPE) and compressor start-up (LPS) so start transients don't nuisance-trip it. Reset is selectable between manual and semi-automatic — semi-automatic clears once the pressure rises above LPt plus the differential (LPU), and after the maximum number of automatic resets (LPo) the alarm requires a manual reset.

Symptoms

• Display shows LP and the unit is stopped
• Suction pressure on gauges reads below the trip threshold
• Trips cluster at compressor start-up, or after the unit has been running iced-up or starved
• Poor or no cooling before the trip

Common causes

• Refrigerant undercharge from a leak
• Iced or airflow-starved evaporator (failed fan, blocked coil, defrost problem)
• Blocked filter-drier or restricted/failed expansion device
• Liquid-line solenoid not opening
• Low ambient at the condensing section pulling suction pressure down

Diagnostic steps

1. 01

   Look at the evaporator first

   An iced coil or a dead evaporator fan starves the suction side. Check airflow, ice, and that defrost is working before touching the refrigerant circuit.

2. 02

   Gauge the suction side

   Confirm the actual suction pressure against the threshold. Note whether the trip happens at start-up (transient, delay may be set too tight) or in steady running (real starvation).

3. 03

   Check for restrictions

   Feel for a temperature drop across the filter-drier and verify the liquid solenoid opens — a restriction or a closed solenoid starves the evaporator and pulls suction down.

4. 04

   Leak-check if undercharged

   Low charge is the most common steady-state LP cause; find and fix the leak rather than topping up.

When to call a professional

Charge verification, leak search and repair, and expansion-device or drier replacement are sealed-system work for a certified refrigeration technician. If LP trips persist after airflow and defrost check out, the refrigerant circuit needs professional diagnosis.