Natural Refrigerants: What Commercial Plant Actually Moves To

Three quotes sat on an estates manager's desk in Croydon this spring, all for replacing the same tired R404A pack behind a convenience store. One proposed CO₂, one proposed propane, one proposed a lower-GWP blend, and all three used the phrase "future-proof". Not one of them said where the plant would sit, what the surrounding space would have to become, or which engineers on his existing contract were competent to touch the result.

He asked me which was right. The honest answer was that the refrigerant was the easiest part of the decision, and the only part any of the three had written down.

Three natural refrigerants are in real commercial use in the UK. R290 propane suits integral cabinets, small packs and packaged chillers, and it is flammable, which caps the charge and dictates where the equipment can stand. R744 carbon dioxide suits retail packs and larger systems, and it works above pressures that need different components and differently trained people. R717 ammonia is an industrial refrigerant and is toxic, which is why you rarely see it on a high street. Lower-GWP HFO blends sit in the middle and stay inside the F-Gas quota. None of them is a drop-in.

What "natural refrigerant" means, and what it does not

The F-Gas rules cover a defined set of chemicals. GOV.UK opens its list with the scope: "If you work with hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) or sulphur hexafluoride (SF6) (F gases), you must follow the guidance for F gas users, producers and traders." (Fluorinated gases (F gases), GOV.UK).

Propane, carbon dioxide and ammonia are none of those things. Search that list for R-290, R-744 or R-717 as refrigerants in their own right and you will not find them, which is the point. They carry no quota, so the supply squeeze tightening around high-GWP HFCs does not reach them. We have covered the January 2027 quota step separately, and this post picks up where that one stops.

Being outside the quota does not put these gases outside every other law. It moves the burden. Instead of quota and CO₂ equivalent you are dealing with flammability, pressure and toxicity, governed by fire and explosion law, pressure systems law and occupational exposure limits. The paperwork does not disappear. It changes desks.

R290 propane: the charge limit is the design constraint

Propane is a good refrigerant. It is efficient, it works with conventional oils and copper, and the components are familiar. Its problem is that it burns.

Under the ISO 817 scheme, refrigerants carry a toxicity letter and a flammability number. Bitzer puts the A3 group plainly: "Group A3 refrigerants are extremely flammable and can ignite at concentrations of two to ten per cent in the air." (A2L and A3 refrigerants, Bitzer). R290 is A3, and that is why the trade argues about charge limits rather than efficiency.

The standard governing self-contained commercial cabinets is IEC 60335-2-89, which the IEC describes as specifying "safety requirements for electrically operated commercial refrigerating appliances and ice-makers that have an incorporated motor-compressor or split systems", while excluding "split systems having a refrigerant charge of flammable refrigerant exceeding 150 g in any refrigerating circuit" (IEC 60335-2-89:2019, IEC Webstore). Its 2019 edition is what changed the market. Danfoss summarises it as: "The charge limits have increased from 150g to 500g for the most flammable A3" refrigerants, and "from 150g to 1.2kg" for the milder A2 and A2L group (IEC 60335-2-89 flammable refrigerant limit change, Danfoss). Secop states the same limits against the classes: "For propane and isobutane in safety class A3 it means 500 g and for classes A2 and A2L 1,200 g per one circuit" (Safety standards for flammable refrigerants, Secop).

Two details in that same guidance matter more on site than the headline number. Danfoss notes that "Remote condensing units should not have more than 150g" per circuit, and that the circuit must be sealed, so "soldered connections are acceptable but flare connections are not". Secop lists among the required measures "appliance marking with the minimum floor area in which it is permitted to be installed".

Read that last one twice. A propane cabinet is marked with the smallest room it is allowed to live in. I have stood in a basement prep area where three R290 units had been wheeled in side by side because that was the only free wall, and nobody had added up the floor area against what the plates said. Nothing had gone wrong. Nothing had been checked either.

The charge cap is also why hydrocarbon refrigerant dominates integral cabinets, bottle coolers and small packaged plant and is rare on a distributed system feeding a dozen cases. You cannot hold enough gas. The usual answer for a larger duty is a packaged propane chiller outdoors with a glycol loop indoors, which is the practical appeal of secondary refrigerant systems: the flammable charge stays in one sealed unit in open air, and what circulates through the building is not flammable at all.

Wherever propane goes, DSEAR applies. HSE sets out duties including that employers "find out what dangerous substances are in their workplace and what the risks are" and "identify and classify areas of the workplace where explosive atmospheres may occur and avoid ignition sources (from unprotected equipment, for example) in those areas" (Dangerous Substances and Explosive Atmospheres, HSE). Bitzer is specific about how that lands on plant: semi-hermetic propane systems are typically treated as "hazardous zone 2 (only seldom and short term risk)", while open compressors may sit in zone 1 and need "electrical equipment in special flame-proof design" (R290 (Propane) as alternative refrigerant, Bitzer).

R744 carbon dioxide: pressure changes everything downstream

With CO₂ the physics forces the engineering. Bitzer states it directly: "Above its critical point, 31.1°C and 73.8 bar(a), CO₂ has no distinguishable difference between its gas and liquid phases." (Operating instruction for Bitzer CO₂ booster rack, BAO-107-1 AU). A British summer regularly puts ambient air above 31°C, so on those days heat rejection cannot happen by condensing. It happens in a gas cooler in the supercritical region, and Bitzer's application guidance gives the operating consequence: "As long as operation remains above the critical pressure (74 bar), only high-density vapour will be transported." (Transcritical CO₂ applications, Bitzer).

Those numbers land on your bill of materials. Bitzer rates its subcritical CO₂ compressors with a "High pressure side up to 53 bar" and a "Low pressure side up to 30 bar", its ME series models "suit pressures up to 100 bar", and its booster racks are specified with 40 bar and 25 bar relief valves (R744 CO₂ systems, Bitzer BA-508-3 AU). Every valve, joint, gauge and relief device is a different part from the one on an R404A pack, and so is the brazing standard expected of whoever fits it.

CO₂ is not toxic the way ammonia is, but it is not inert. HSE's approved workplace exposure limits give carbon dioxide 5,000 ppm over eight hours and 15,000 ppm over 15 minutes, in a list that "is legally binding, as it reproduces the list of workplace exposure limits (WELs) which have been approved by the Health and Safety Executive" (EH40/2005 Workplace exposure limits, HSE). Bitzer explains why that matters in a basement: "CO₂ is heavier than air, and may accumulate in an isolated or non-ventilated space if there is a refrigerant leak and/or activated pressure relief into such spaces." Detection and ventilation are part of a CO₂ plant, not an extra.

Where CO₂ earns its place, heat reclaim included, is set out on our page about transcritical CO₂ systems. The point here is narrower. Choosing R744 is choosing a different plant room, a different spares list and a different competence requirement for whoever holds the service contract.

R717 ammonia: excellent, industrial, rarely right on a high street

Ammonia is thermodynamically the best of the three and has been used in industrial refrigeration for well over a century. It is also toxic, and that decides where it can go.

Bitzer classifies R717 as "group B2L (EN378-1)", notes its "High toxicity" and an "Intense odour" at low concentration, and describes it as "Explosive between approx. 15 .. 30 vol. % in air" with a high ignition temperature of 651°C (Properties of R717, Bitzer). It is equally blunt about competence: "Evidence of the staff's special expertise in installation, commissioning, operation and service is required."

HSE's EH40 gives ammonia, anhydrous a long-term workplace exposure limit of 25 ppm and a short-term limit of 35 ppm. Set that beside carbon dioxide's 5,000 ppm in the same table and the difference in required containment is obvious. Ammonia belongs to cold stores, food factories and process plant with dedicated machinery rooms and trained operators. Any quote offering it for a small retail or hospitality site deserves a very careful second reading.

The middle ground: lower-GWP blends and HFOs

Not every site needs to jump to a natural refrigerant. Blends stay inside the F-Gas quota and remain exposed to the phase-down, but a much lower GWP means a given charge burns far less of it. These figures are from the GOV.UK list, where "Global warming potential (GWP) figures in these tables are rounded to the nearest whole number".

Refrigerant	GWP (GOV.UK)	Position
R-404A	3,922	The gas everyone is leaving
R-410A	2,088	Air conditioning and some refrigeration
HFC-134a	1,430	Cabinets, bottle coolers, chillers
R-448A	1,386	Common R404A replacement
HFC-32	675	Widely used in newer air conditioning
HFC-1234yf	4	HFO, a component of newer blends
R-290, R-744, R-717	Not on the list	Not F gases, outside the quota

One warning about that table. Several blends being actively sold in Britain right now, including R-449A, R-450A, R-455A and the R-454 family, do not appear on the GOV.UK list at all. If a contractor proposes one, you cannot look its GWP up on that page and will need the manufacturer's data instead. Worth knowing before you write a specification saying "GWP to be verified against the GOV.UK list". GOV.UK's own advice is that "If you use or service equipment containing HFCs, ask your supplier for advice on alternatives", and the sensible reading is to make the supplier put the number in writing.

Retrofitting onto a lower-GWP blend is a real option and sometimes the right one, but it is an assessment rather than an assumption. Oil, compressor, expansion device, seals and controls all have a say, and our page on the repair versus replace decision covers how that judgement usually goes.

What each choice does to your plant room and your contract

	R290 propane	R744 CO₂	R717 ammonia
Safety class	A3, extremely flammable	A1, not flammable	B2L, toxic
Main constraint	Charge limit and room size	Operating pressure	Toxicity and containment
Typical fit	Integral cabinets, small packs, packaged chillers	Retail packs, booster systems, larger estates	Cold stores, food factories, process plant
Plant room implication	DSEAR zoning, ventilation, marked minimum floor area	High-pressure components throughout, gas detection, relief routed safely	Dedicated machinery room, detection, emergency procedures
Spares and tooling	Mostly familiar, sealed circuits, no flares	Different valves, gauges, relief devices, brazing standard	Steel pipework, specialist components
Contract implication	Trained on hydrocarbons, DSEAR-aware	Trained on transcritical, out-of-hours competence matters more	Specialist industrial contractor

There is a legal layer underneath that surprises people. The Pressure Systems Safety Regulations 2000 exempt, at Schedule 1, "Any vapour compression refrigeration system incorporating compressor drive motors, including standby compressor motors, having a total installed power not exceeding 25 kW" (PSSR 2000, Schedule 1). Above that, regulation 8 requires that the user "shall not operate" the system without a written scheme of examination drawn up or certified by a competent person (regulation 8, written scheme of examination). That threshold is about installed compressor power rather than refrigerant, so it can catch a large HFC pack just as easily. People simply tend to discover it while specifying CO₂. The design standard to name in a specification, incidentally, is BS EN 378-1:2016+A1:2020, not a gas.

How to read a quote that says "future-proof"

• What is the charge, and what does the plate say about the space it needs? On a hydrocarbon, the marked minimum floor area is a hard constraint.
• Where does the plant go, and what changes about that space? Ventilation, gas detection, electrical zoning and where a relief device discharges are part of the price and are commonly left out of the headline figure.
• Who services it, and can they evidence the competence? Ask by name rather than accepting "our engineers are trained". A CO₂ rack at two in the morning is not the moment to find out.
• Is it in scope of PSSR, and who writes the written scheme? Installed compressor power decides it. Settle that before installation, not at the first insurance inspection.
• What happens to the old refrigerant? Recovery and the record of it remain your responsibility as operator, as our guide to F-Gas compliance basics explains.

Ask those five of all three bidders and the quotes stop being interchangeable. In the Croydon case one supplier answered all five within a day, one answered three, and one asked why it mattered. That told the estates manager more than the technical schedules did.

Across an estate rather than one site

The common mistake is treating this as a single decision made centrally and applied everywhere. Estates are not uniform. A convenience format on integral cabinets is an obvious R290 candidate. A large store on a distributed pack is a CO₂ conversation. A leased unit where the landlord controls the plant room may be neither, because the constraint is the lease rather than the engineering. The R410A phase-down is doing something similar to the air conditioning in the same buildings, on its own timetable.

What works is a register of plant carrying refrigerant, charge, age and installed power on every line, then a replacement sequence built around the worst-exposed sites. That gives you a capital plan instead of a run of emergencies, and it gives whoever holds your planned refrigeration servicing a fair chance of having the competence and the parts in place before the new plant arrives rather than after.

One honest point to finish on. Every refrigerant you add to an estate widens the competence your contractor needs, and that is a real cost nobody puts in the business case. It is not an argument against natural refrigerants. It is an argument for sequencing them, so you are not running three technologies across twenty sites with a provider trained on one.

Frequently asked questions

Which natural refrigerants are actually used in UK commercial refrigeration?

Three, in practice. R290 propane in integral cabinets, small packs and packaged chillers. R744 carbon dioxide in retail packs, booster systems and larger installations. R717 ammonia in industrial cold storage and food processing. Isobutane, R600a, turns up in smaller sealed appliances and behaves like propane from a safety point of view. None is a fluorinated gas, so none carries F-Gas quota.

What is the R290 charge limit?

For self-contained commercial refrigerating appliances, IEC 60335-2-89:2019 raised the limit for A3 refrigerants such as propane from 150 g to 500 g per circuit, with 1.2 kg allowed for the milder A2 and A2L group. That standard does not cover split systems holding more than 150 g of flammable refrigerant in any circuit, and Danfoss notes remote condensing units should not exceed 150 g per circuit. The figure that governs your installation is the one on the appliance plate, along with the minimum floor area marked on it.

Is R290 safe in a commercial kitchen or on a shop floor?

It is used in exactly those places in very large numbers, and it is safe when equipment is installed as marked and treated as a dangerous substance under DSEAR. What makes it unsafe is ordinary: units crowded into an undersized room, ventilation blocked, a circuit opened by somebody who did not know what was in it, or a repair attempted with flare fittings on a circuit that has to stay sealed. Propane is not a reason for alarm. It is a reason to control who works on the plant.

Can I convert an existing R404A system to propane or CO₂?

No. Both are new systems rather than conversions. Propane needs a circuit designed for a flammable charge with the associated electrical and ventilation measures, and CO₂ operates at pressures your existing components are not rated for. What can sometimes be retrofitted is a lower-GWP HFC or HFO blend, and even that depends on the oil, compressor, expansion device and controls. Anyone offering to put a natural refrigerant into existing pipework should be asked to put it in writing.

Does a CO₂ system need a different maintenance contract?

The visit structure looks similar. What changes underneath is the competence of the attending engineer, the parts held, the pressure ratings of anything fitted and the way detection and relief devices are checked. If one site moves to CO₂ while the rest of the estate stays on HFCs, confirm in writing that out-of-hours attendance for that site is covered by someone trained on transcritical plant. A general refrigeration engineer will not necessarily be, and that turns a routine commercial refrigeration repair across London into a wait for a specialist.

Why is ammonia not used in shops and restaurants?

Toxicity. HSE's legally binding exposure limits put ammonia at 25 ppm over eight hours and 35 ppm over 15 minutes, a small fraction of what is allowed for carbon dioxide. Containing it safely takes a dedicated machinery room, detection, emergency procedures and staff with demonstrated expertise. That is realistic for a cold store or a food factory and unrealistic above a restaurant kitchen.

Deciding this before it decides itself

Every business I know that came through the R404A squeeze in reasonable shape made its refrigerant decisions in an office, with a list in front of it. The ones that suffered made them on a Saturday, with a dead pack, whatever gas the wholesaler could release and a contractor who had one option to offer.

The refrigerant is the easy half of the choice. The plant room, the competence and the contract are the half that decides whether it works. Talk to us about R744 systems and the alternatives, and we will go through your plant honestly, including the sites where the sensible answer is to leave what you have alone for now.

About the author: Ali Elm runs Be Cool Refrigeration & Air Conditioning, a family-run London firm that has been installing, servicing and repairing commercial refrigeration and air conditioning since 2004. His F-Gas certified team has delivered more than 2,000 projects across London and the South East.

Last updated: 11 September 2026