BOCK HG/HGX — German semi-hermetic recip for industrial duty
By DigiEntropy Engineering · 2026-03-08 · 5 min read
BOCK's HG and HGX families are the German engineering standard for industrial semi-hermetic reciprocating compressors. R744-qualified ECOLINE-equivalent variants, ammonia industrial, transport refrigeration — BOCK covers ranges where Bitzer doesn't quite fit.
About this post — Authored by an AI assistant using DigiEntropy's polynomial corpus, the universal compressor predictor, and the project's chart-generation tooling. Charts are produced by Python scripts that read the same database the live site queries; tables and formulas are pulled from the same engineering modules. Findings reflect the project's current dataset and methodology — send corrections or deeper questions to admin@digientropy.com. BOCK Kältemaschinen (founded 1932, now part of GEA) makes a specific kind of compressor: semi-hermetic reciprocating, German-engineered, optimised for industrial-duty cycles. The HG and HGX families are the workhorses — HG for general industrial, HGX for the F-Gas-era extended-envelope variants. BOCK sits in DigiEntropy as one of the longest-tail brand integrations, with a transparent decoded catalog covering most of the industrial commercial refrigeration sizes Bitzer doesn't quite specialise in. Where BOCK wins Three niches where BOCK is the default rather than the alternative: 1. Transport refrigeration. BOCK's HGX12 and HG12 series are widely used in truck/trailer refrigeration (Carrier Transicold, Thermo King, and others ship BOCK compressors in their TRU units). The compressors are designed for the vibration / shock / wide-ambient envelope that truck refrigeration demands. 2. R744 transcritical industrial. BOCK's HGX CO2 variants compete strongly with Bitzer ECOLINE CO2 in the 20-100 kW per compressor range. Both brands have mature transcritical lines; BOCK is often spec'd when the customer wants supplier diversity from Bitzer. 3. Ammonia industrial cold storage. BOCK's HG ammonia variants are deployed extensively in mid-size (200-1000 kW) industrial cold storage, particularly in central and eastern Europe. The HG family is the legacy line; HGX is the post-2010 update with extended envelope + A2L qualification on newer variants. Reading a BOCK part number BOCK part numbers follow: Examples: - HGX22e-160-4: HGX 22 family (medium size), e suffix (Ecoline), capacity index 160, 4-pole motor - HGX34e-315-4: HGX 34 family (large), capacity index 315 - HGX12P/110-4 S: HGX 12 family (transport), P (positive displacement) / 110 capacity, 4-pole motor The size code (12, 22, 34, etc.) maps to bore × stroke geometry. The e suffix is "ECOLINE" — BOCK's extended-envelope variants that match Bitzer's ECOLINE branding for the same regulatory drivers. Engineering differences vs Bitzer Octagon Both BOCK HGX and Bitzer Octagon are semi-hermetic reciprocating compressors with similar thermodynamic operating ranges. Engineering…