The Bitzer Octagon family explained — HE, HES, FE, GE, JE, EES, CES
By DigiEntropy Engineering · 2026-03-07 · 6 min read
Bitzer's Octagon family is the EU reference for semi-hermetic reciprocating compressors. The letter classes (HE, HES, FE, GE, JE, EES, CES) encode bore + stroke + cylinder count. Knowing the system lets you pick the right model from a part number alone.
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.
Bitzer's Octagon family of semi-hermetic reciprocating compressors is the EU reference for commercial + light-industrial refrigeration. From the smallest 2HES to the largest 8GE, the family covers 3 kW to 200 kW per compressor with consistent geometry conventions.
The naming system is denser than it looks. "4HE-25Y" tells you, in 5 characters: 4-cylinder, HE-family geometry, 25 capacity index, Y suffix for European voltage option. Knowing the system lets you read a part number like a sentence and immediately understand the compressor.
This post is the decoder.
200 kW - top of the family - from 3 kW per compressor
From the smallest 2HES to the largest 8GE, the family covers 3 kW to 200 kW per compressor with consistent geometry conventions.
70 × 55 - HE bore × stroke, mm - the mid-commercial workhorse
HE class: 70 × 55 mm bore × stroke, 8-40 kW, mid-commercial refrigeration. The HE and FE families are the workhorses of mid-commercial.
1.5× - displacement, 6HE over 4HE - same geometry, more cylinders
Same HE geometry as 4HE but with 6 cylinders. The 6/4 cylinder ratio = 1.5× displacement; capacity index goes 25 → 35.
25 kW - 4HE-25Y Qe at MT - -10/40 °C, R448A
The 4HE-25Y: 4-cylinder, 70 × 55 mm bore × stroke, 25 kW Qe at MT (-10/40 °C R448A).
±20 % - 4HE-25Y capacity swing - across the typical envelope
The 25 kW Qe nameplate is at the standard -10/40 °C condition; capacity varies ±20 % across the typical operating envelope.
15-50 kW - where HE, FE and JE overlap - price + lead-time decides
The classes overlap heavily in the mid-commercial band — HE + FE + JE all serve 15-50 kW with slight geometry differences. Picking between them is usually price + lead-time, not engineering.
The letter classes
Each letter class encodes a (bore × stroke) geometry. Across the class, cylinder count scales the displacement; the geometry stays constant.
The letter classes: capacity range and geometry - Capacity range
Capacity range, low end: HES 1 kW, HE 8 kW, FE 5 kW, GE 30 kW, JE 5 kW, EES 2 kW, CES 1 kW, VES 1 kW.
Capacity range, high end: HES 5 kW, HE 40 kW, FE 25 kW, GE 120 kW, JE 25 kW, EES 15 kW, CES 8 kW, VES 5 kW.
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