HIT

Hitachi 43

Critical

Set Free Sigma / IVX (FSXN) — Activation of the low compression ratio protection device

Hitachi 43: Activation of the low compression ratio protection device This fault typically halts operation and needs immediate attention.

Possible causes

Inverter malfunction or compressor failure
Reversing valve stopped at middle position or solenoid valve (SVA) leakage

Check steps

Calculate compression ratio Ɛ = ((Pd+0.1)/(Ps+0.06)); check inverter and compressor operation
Check valve positioning and high/low pressure sensors, replace faulty components

Affected parts

Compressor
4-way reversing valve
Solenoid valve SVA
High/low pressure sensor

Safety note

High-pressure refrigerant circuit — safely relieve pressure before intervention, wear protective equipment.

Source: Hitachi resmi servis kılavuzu (bağımsız çift-doğrulandı) — Hitachi FSXN Series Service Manual, Troubleshooting by alarm code, p.222 (manualslib.com/manual/2375584, page=222): Alarm code 43 — "Excessively Low Compression Ratio" — "Activation of the low compression ratio protection device." Ɛ = (Pd+0.1)/(Ps+0.06); condition Ɛ < 1.8 occurring three times within one hour trigg…

Reviewed by Anıl Güzeldemir — in the refrigeration machine room since 2006, developer of Enthalio.

Look up in Enthalio →

Related fault codes

Activation of the indoor unit protection devic01 Abnormal transmission between outdoor units (H0A Incorrect outdoor main unit address configurat0C Activation of the low pressure increase protec44 Activation of the high-pressure increase prote45 Vacuum operation protection / excessively low 47