Hitachi 44

High

Set Free Sigma / IVX (FSXN) — Activation of the low pressure increase protection device

Hitachi 44: Activation of the low pressure increase protection device This fault noticeably affects operation.

Possible causes

Solenoid valve (SVA) leakage or reversing valve not at middle position
Abnormal low-pressure sensor or excessively high intake air temperature

Check steps

Check solenoid valve outlet pipe temperature and reversing valve suction gas pipe temperature
Verify sensor connections and thermistor readings, replace faulty components

Affected parts

Low pressure sensor
Solenoid valve SVA
4-way reversing valve

Safety note

Refrigerant circuit is pressurized — depressurize the system before intervention.

Source: Hitachi resmi servis kılavuzu (bağımsız çift-doğrulandı) — Hitachi FSXN Series Service Manual, §8 Troubleshooting by Alarm Code, p.223 (manualslib.com/manual/2375584/Hitachi-Fsxn-Series.html?page=223): Alarm code 44 = "Activation of the low pressure increase protection device" (Niederdruck-Anstiegsschutz). Trigger: compressor operates with suction pressure (Ps) greater than…

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