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Process and glycol chillers for manufacturing and brewing

Updated 23 October 2026 · SEO Dons Editorial

How does a process chiller differ from a comfort chiller?

The ecodesign regulation for process chillers defines one as a product integrating at least one compressor and one evaporator, capable of cooling down and continuously maintaining the temperature of a liquid in order to provide cooling to a refrigerated appliance or system. The companion regulation for high temperature process chillers adds that the purpose is not to provide cooling of a space for the thermal comfort of human beings. Typical users are manufacturing, plastics, food and drink, and brewing, where a machine or vessel sets the load.

The regulations also fix three rating points, which matter when you compare datasheets: a high temperature chiller is rated at an outlet temperature of 7 °C, a medium temperature one at -8 °C and a low temperature one at -25 °C. Cold rooms and catering chillers are a separate subject, and the comfort side is in the types of chillers guide.

Why is glycol used, and what does it change?

A loop that runs near or below freezing, or that sits outdoors in winter, needs an antifreeze. CIBSE Journal notes that a mixture of 75% water and 25% propylene glycol is commonly used for a technology cooling loop, or sometimes ethylene glycol. For food and drink sites the fluid choice matters: Dow describes its inhibited propylene glycol product as made entirely from food-grade raw materials and acceptable as a heat transfer fluid where incidental food contact is possible.

Suppliers publish freeze protection and burst protection figures for each concentration. Dow's page, for example, claims freeze protection below -50 °C and burst protection below -73 °C for solutions of its fluid in water, which shows the range, not a value to design to.

A glycol mixture is not water. Its heat capacity and viscosity differ, so the pump, the heat exchangers and the chiller evaporator must be selected on the mixture's published data at your concentration, which the glycol supplier provides.

How is a process chiller sized?

  1. Establish the heat load from the process equipment's datasheets or from measurement, in kilowatts, including peak and normal values.
  2. Cross-check the duty from the liquid flow. CIBSE Journal gives the method: the heat carried is the mass flow rate multiplied by the temperature difference between the entering and leaving liquid and by its mean specific heat capacity.
  3. Add allowances for pump heat, pipework gains and planned expansion, then decide how much margin the process can justify.
  4. Fix the setpoint and the temperature difference, because they decide the chiller class and the ecodesign rules that apply.
  5. Choose the design ambient and the heat rejection route, air-cooled or water-cooled.
  6. Decide turndown and redundancy: several smaller chillers in parallel, with a standby unit where a stoppage is costly. A buffer volume steadies the loop, and some packaged chillers include a hydronic unit with a buffer tank and pump.

Illustrative arithmetic with assumed values: a loop circulating 2 kg/s of a glycol mixture with an assumed specific heat of 3.8 kJ/kg K and a 5 K temperature rise carries 2 x 3.8 x 5 = 38 kW. Take the real specific heat from the glycol supplier's data for your concentration.

Which ecodesign rules apply to a process chiller?

It depends on the rated outlet temperature. The regulation for high temperature process chillers excludes products with leaving chilled water below 2 °C or above 12 °C, while the process chiller regulation covers products intended to operate at low or medium temperature and excludes high temperature ones. Both exclude custom-made chillers assembled on site on a one-off basis and chillers exclusively using evaporative condensing, and the process chiller regulation also excludes absorption chillers.

Rated outletRegulation and start dateAir-cooled minimum SEPRWater-cooled minimum SEPR
7 °C (high temperature)2016/2281, from 1 January 20215.0 under 400 kW; 5.5 from 400 kW7.0 under 400 kW; 8.0 from 400 to under 1,500 kW; 8.5 from 1,500 kW
-8 °C (medium temperature)2015/1095, from 1 July 20182.58 up to 300 kW; 3.22 above 300 kW3.29 up to 300 kW; 4.37 above 300 kW
-25 °C (low temperature)2015/1095, from 1 July 20181.70 up to 200 kW; 1.84 above 200 kW2.09 up to 200 kW; 2.42 above 200 kW

SEPR, the seasonal energy performance ratio, is the annual cooling demand divided by annual electricity consumption. For process chillers charged with a refrigerant of global warming potential below 150, the process chiller values may be up to 10% lower. The ETL's higher listing thresholds for high temperature process chillers start at 6.10 for air-cooled units under 400 kW and 7.40 for water-cooled ones. Ask the supplier for the declared SEPR and the regulation it was declared under.

Can free cooling help a process loop?

Often, on warmer loops. One manufacturer of free-cooling units describes the sequence: when the ambient air is 1 °C below the process fluid return temperature a three-way valve diverts the return through a free-cooling coil for partial free cooling, and at 5 °C below the process supply temperature the air removes all the heat. It adds that a standalone free-cooling system can work alongside an existing chiller. Daikin Applied lists a screw chiller version in which the glycol is confined to a closed loop.

The arithmetic cuts against cold duties. On that rule a loop supplying at 15 °C reaches full free cooling when the air is about 10 °C or less, but a loop at -5 °C would need air at -10 °C, so the benefit is small. The hours available by region are in the free cooling chillers by UK region guide.

What F-gas duties come with a process chiller?

Government guidance sets the leak-check frequency by the carbon dioxide equivalent of the charge: at least every 12 months from 5 tonnes, every 6 months from 50 tonnes, and a leak detection system is required at 500 tonnes or more for most equipment. The same guidance shows that 35 kg of HFC 134a sits at the 50 tonne line, so a chiller holding 40 kg of it falls into six-monthly checks. Lower-GWP refrigerants change the arithmetic (see chiller refrigerants), and the wider duties are in F-gas regulations explained.

For plant serving a factory or brewery, the industrial air conditioning page sets the context, and the commercial chillers page explains the selection process. You can send an enquiry through the site's form.

Sources

Regulations and guidance are revised, so confirm the current text before relying on a figure.

Common questions

Do I need a glycol chiller or a water chiller?

Use glycol if the loop will run near or below 0 °C, or if it can sit outdoors in freezing weather. The ETL treats chilled water flow temperatures from 2 °C to 12 °C as high temperature process chilling, so loops in that band may avoid glycol if they are protected from frost.

Can a comfort chiller be used for process cooling?

Some ranges are offered for both: Daikin Applied lists a small air-cooled scroll chiller able to cover comfort cooling and process cooling needs. Check the rated outlet temperature, the operating range and the duty cycle, because process loads often run all year.

Is propylene glycol safe near food?

Dow describes its inhibited propylene glycol fluid as acceptable where incidental food contact is possible. That is a statement about one product. Confirm suitability with the glycol supplier for your process and keep the product data sheet with the plant records.

Does a process chiller have to meet a minimum efficiency?

Yes, unless it falls under an exclusion such as a custom-made unit assembled on site. The minimum SEPR depends on the rated outlet temperature, the heat rejection method and the capacity band shown in the table above.

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