Industrial refrigeration plant: ammonia, CO₂ and cascade compressor systems
Industrial refrigeration plant · Compressor racks and condensing units for cold stores, freezers and low-temperature processes: refrigerant choice, evaporating range, machinery-room safety, leak-rate rules
An industrial refrigeration system here means the plant that produces cold for a building or process: compressors, oil separation, condenser, receiver, valves and controls, built as a rack or a condensing unit and piped to evaporators in the cold rooms or freezers. The refrigerant then sets the operating pressure, where the plant may stand, what safety equipment the machinery room needs and which leak rules apply.
Compressor racks, condensing units and machinery-room refrigeration packages for cold stores, food freezers and low-temperature process cooling, with ammonia, CO₂, cascade or HFC refrigerants. This differs from the refrigeration built into a freeze dryer to chill its shelves and condenser: freeze dryers are covered on the Pharmaceutical freeze dryer (lyophilizer) page. Water chillers, domestic refrigerators and valves or panels sold alone are outside this page. A single air-cooled condensing unit serving one cold room or walk-in is a smaller, separately rated product; that case is on the Refrigeration condensing units for cold rooms page.
CNFX editorial research · Sources checked October 12, 2026 · 3 sources
Square's description of its industrial racks sets out the trade-off. Ammonia (R717) has a GWP and ODP of 0 but is classed B2L, toxic and mildly flammable, and needs safety systems to EN 378. CO₂ (R744) is non-toxic and non-flammable (A1) with a GWP of 1, but runs at much higher pressure, about 40 bar at −5 °C against about 3 bar for ammonia. In a cascade, ammonia stays on the high-temperature side in the machinery room and CO₂ is circulated to the production areas. [1]
Square points CO₂ at sites where the ammonia charge is restricted or the equipment room is indoors, and the cascade at plants that want ammonia's efficiency with CO₂ in occupied spaces. Its racks use open-drive reciprocating or single and twin screw compressors, with evaporative, air-cooled or water-cooled shell-and-tube condensers, and pressure vessels built to ASME or, on request, PED. [1]
Editorial calculation: 40 bar ÷ 3 bar ≈ 13, so CO₂ piping, vessels and valves at −5 °C see roughly thirteen times the pressure of an ammonia system at the same temperature, using Square's rounded figures. [1]
Give the supplier the cooling loads for each room or freezer with their room temperatures, the product and its throughput, the site's hottest ambient and wet-bulb temperature, where the machinery room can be, any limit on ammonia charge, and the electrical supply.
02
Set evaporating and condensing temperatures, then size the compressors
Square lists evaporating temperatures of −45 °C to +10 °C and condensing temperatures of +25 °C to +45 °C depending on ambient, with system capacities from 50 kW to over 5 MW. It uses screw compressors of 200 kW to over 2 MW per unit for medium to large plants with varying load, and reciprocating compressors of 50–300 kW per unit with cylinder unloading for smaller plants, adding compressor sequencing and variable-frequency control across the operating range. [1]
Zhiyun's condensing units cover evaporating temperatures from −40 °C to +12 °C and can be set up for medium-to-high, medium-to-low or low-temperature storage. It offers scroll, semi-hermetic reciprocating and screw compressors in box-type, open-type and screw units, with air-cooled, water-cooled and evaporative-cooled condensing. [2]
A freezer room and a chill room on the same plant run at different evaporating temperatures, so the quotation should list each load at its own evaporating temperature rather than one total in kW. Square's racks run the compressors, condensers and defrost cycles from one PLC controller. [1]
03
Equip the ammonia machinery room before the plant is charged
For ammonia plants Square designs to EN 378 in Europe or ASHRAE 15 and IIAR in North America, with continuous ammonia detection that warns at 25 ppm and starts emergency ventilation at 150 ppm, mechanical ventilation rated for 30 air changes per hour on detection, relief valves piped to a safe location and sized to EN 13136 or ASHRAE 15, emergency stop stations and automatic shutdown on high gas concentration. [1]
Square's machinery room requirements include gas-tight construction, doors opening outward and light switches outside the room. [1]
Editorial calculation: 30 air changes per hour in a machinery room of 10 × 8 × 5 m (400 m³) is 12,000 m³/h of emergency extract. The room size is an assumed example. [1]
04
Plan for EPA leak-rate limits on HFC plants from 2026
In the United States, 40 CFR 84.106 applies from 1 January 2026 to refrigerant-containing appliances with a full charge of 15 lb or more of a regulated HFC or a substitute with a GWP above 53. Owners must calculate the leak rate whenever refrigerant is added, and repair leaks within 30 days, or 120 days if an industrial process shutdown is needed, when the rate exceeds 20% for commercial refrigeration, 30% for industrial process refrigeration or 10% for comfort cooling and other appliances. [3]
After a plant has exceeded its limit, leak inspections are due once every three months for commercial and industrial process refrigeration with a full charge of 500 lb or more, until four quarters in a row show the rate has not been exceeded, and once a year for charges of 15 lb up to 500 lb, until one year shows it has not been exceeded. [3]
Editorial calculation: 15 lb ≈ 6.8 kg and 500 lb ≈ 227 kg (1 lb = 0.4536 kg). An HFC rack holding more than about 227 kg therefore falls in the quarterly inspection band after an exceedance. [3]
05
Recover discharge and condenser heat
Square lists three heat sources on its racks: a desuperheater on the compressor discharge gas at 70–90 °C for hot water, oil-cooler heat for underfloor heating or pre-heating, and condenser heat at 25–35 °C for space heating or defrost water. It states savings of 15–30% in facility heating costs, a figure from the maker rather than a measured result for a given site. [1]
Square gives a lead time of 16–22 weeks for a custom-engineered system and states that factory-assembled skids cut on-site work by 40–60%. [1]
Square lists NH₃, CO₂ and cascade racks, Zhiyun lists condensing units for −40 °C to +12 °C, and Emford lists parallel-compressor units for cold stores.
Square Technology Group Co. Ltd.
Manufacturing site to be confirmed for the order
Lists industrial refrigeration racks with NH₃, CO₂ and cascade NH₃–CO₂ refrigerants for freezers and cold storage.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What evaporating temperatures do these plants reach?
Square lists −45 °C to +10 °C for its industrial racks and Zhiyun −40 °C to +12 °C for its condensing units. [1][2]
Why choose CO₂ instead of ammonia?
Square notes CO₂ is non-toxic and non-flammable with a GWP of 1, but runs at about 40 bar at −5 °C against about 3 bar for ammonia. [1]
Which US leak-rate limits apply to an HFC refrigeration plant?
From 2026, 40 CFR 84.106 sets 20% for commercial and 30% for industrial process refrigeration for charges of 15 lb or more. [3]
Sources and what still needs a direct check
Sources checked 2026-10-12. Square and Zhiyun are plant makers and their figures describe their own ranges; Square's savings and site-work figures are its own statements. 40 CFR 84.106 is a US EPA regulation.
