Monoblock Refrigeration Unit vs Split System: Choosing for a Cold Room

A monoblock refrigeration unit is one factory-built, factory-charged unit that mounts through the wall or roof of a cold room, with everything in a single housing. A split system puts the evaporator inside the room and a remote condensing unit outside, joined by pipework charged on site.

You will recognise the moment this lands. A new cold room is going in, the panel supplier is asking where the refrigeration will sit, and two quotes arrive offering different answers with no explanation of why. What separates them is where the heat goes, who handles the refrigerant, and what the paperwork looks like for the next decade.

At a glance

Question	Short answer
Do the two layouts need routine F-Gas leak checks?	A monoblock that qualifies as hermetically sealed: no maximum period between checks unless it holds 10 tonnes of CO2 equivalent or more (2.6 kg of HFC-404A or 7 kg of HFC-134a). A split charged on site: at least every 12 months once the charge reaches 5 tonnes, more often at higher bands.
Can you still buy new R404A cold room plant?	No. Stationary refrigeration equipment containing HFCs with a GWP of 2,500 or more is already banned from the GB market.
And hermetically sealed commercial equipment?	Banned now if it contains HFCs with a GWP of 150 or more.
Does the 2025 single split ban affect cold rooms?	No. It covers air conditioning under 3 kg at a GWP above 750, and exempts systems used solely to cool products.

Source: Checking F gas equipment for leaks, GOV.UK and Bans on F gas in new products and equipment, GOV.UK

What a monoblock refrigeration unit actually is

Strip the name back and it is literal: one block. Compressor, condenser, evaporator, expansion device and controls all live in a single factory-assembled housing. It mounts through a cut-out in the panel: through the wall, over the top as a straddle, or on the roof. The cold side faces in, the hot side faces out, separated by the panel.

Because the circuit is completed and charged at the factory, nothing on site involves refrigerant: no pipework, no brazing, no vacuum, no charge. The room gets panels, a cut-out, a power supply and a drain, and the unit is commissioned where it sits.

Monoblocks are generally chosen for small and medium rooms, and freezer-rated versions exist for frozen stock. A large room or a heavy duty can outgrow what one packaged unit can do, and the design moves to a split.

What a split system cold room involves

A split separates the two halves of the refrigeration cycle. The evaporator, usually a ceiling-mounted unit cooler, hangs inside the room. The cold room condensing unit sits somewhere remote: a yard, a flat roof, a wall bracket. Copper pipework joins the two, run, brazed, pressure tested, evacuated and charged on site.

That on-site work is refrigerant handling: F-Gas work. GOV.UK is direct: "You must have your own qualifications to work on equipment containing F gas", and the covered activities include installing, servicing, leak checking and recovery (Qualifications required to work on equipment containing F gas, GOV.UK). A split is therefore commissioned by F-Gas certified engineers as a matter of law, not preference.

The payback is freedom of layout: heat and noise leave the building, servicing happens without anyone entering the room, and one larger pack can serve more than one room.

Monoblock vs split, side by side

Most rows are general trade reality; the charge limit rows come from Danfoss (below) and the leak rows from the GOV.UK guidance linked above.

	Monoblock	Split system
Refrigerant charge	Charged and sealed at the factory	Evacuated and charged on site after brazing
Installation work	Panel cut-out, power supply, drain, commissioning	Pipe runs, brazing, pressure test, vacuum, charge, interconnect wiring
Heat rejection	Into the space immediately beside the room	Outside the building or onto the roof
Compressor noise	At the cold room wall, next to whoever works nearby	At the condensing unit, away from staff but possibly near neighbours
Flammable refrigerant charge limit	500 g per circuit for A3 refrigerants under IEC 60335-2-89	150 g per circuit for a remote condensing unit on flammable gas
Routine F-Gas leak checks	No maximum period while it qualifies as hermetically sealed and holds under 10 tonnes CO2e	At least every 12 months from 5 tonnes CO2e, every 6 months from 50 tonnes

Source: IEC 60335-2-89 flammable refrigerant limit change, Danfoss

Where the heat goes, and where the noise sits

Refrigeration does not destroy heat, it moves it. A monoblock moves it as far as the other side of the panel, which suits a ventilated back area or an outside wall and struggles in a tight basement or hot kitchen, where rejected heat warms the space around the unit and running hours climb. A split sends it outside.

Noise follows the same geometry. A monoblock's compressor runs at the cold room wall and the adjacent workspace hears it all day; a split puts it outdoors, which pleases the kitchen but can displease a neighbour. Neither is quiet by magic; the question is whose ears are nearby.

The F-Gas rules that reach this decision

F gases are a defined list, not every refrigerant. GOV.UK scopes its guidance to "hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) or sulphur hexafluoride (SF6)", with GWP figures "rounded to the nearest whole number" (Fluorinated gases (F gases), GOV.UK). Propane is not on it. What is on it, at high enough GWP, is now banned from new equipment placed on the GB market.

Equipment	Refrigerant scope	GWP threshold	Banned from	Exception
Refrigerators and freezers for commercial use (hermetically sealed equipment)	HFCs	2,500 or more	1 January 2020	None
Refrigerators and freezers for commercial use (hermetically sealed equipment)	HFCs	150 or more	1 January 2022	None
Stationary refrigeration equipment	HFCs	2,500 or more	1 January 2020	Equipment cooling products to below -50 °C
Multipack centralised refrigeration systems of 40 kW or more	F gases	150 or more	1 January 2022	Cascade primary circuit below GWP 1,500
Single split air-conditioning systems under 3 kg	F gases	750 or more	1 January 2025	Systems used solely to cool products, air to water systems, maritime craft

Source: Regulation (EU) No 517/2014, Annex III as retained in GB law, legislation.gov.uk; the single split exceptions are from the GOV.UK bans guidance linked under At a glance

Two readings matter here. The bottom row is an air conditioning ban: the exception for "stationary single split air-conditioning systems which are used solely for the cooling of products" keeps a split cold room outside it. Anyone claiming the 2025 ban forces your cold room onto a particular layout is stretching the rule. The 2,500 threshold is why R404A, listed at 3,922, is finished for new stationary plant. Our guide to replacing R404A covers that gas decision.

The operating rules also bite differently. A monoblock that qualifies as hermetically sealed sits under the GOV.UK carve-out: no maximum period between checks below 10 tonnes of CO2 equivalent, which GOV.UK puts at 2.6 kg of HFC-404A or 7 kg of HFC-134a. Check the charge on the rating plate rather than assuming. A split charged on site enters the routine leak check bands once the charge reaches 5 tonnes CO2e. As of October 2026 these are the GB rules, so confirm your own position with your supplier in writing. Our overview of the F-Gas rules for businesses sets out the operator duties.

Flammable refrigerants, packaged units and DSEAR

Some current monoblocks run on R290 propane, an efficient refrigerant that is also flammable. IEC 60335-2-89, the standard for self-contained commercial appliances, raised its charge limits in 2019: 500 g per circuit for A3 refrigerants such as propane, 1.2 kg for the milder A2 and A2L classes, soldered joints rather than flares, and a marked minimum room floor area on larger charges. Danfoss adds the detail that settles the comparison: "Remote condensing units should not have more than 150g" per circuit. So propane suits a packaged unit far better than a split cold room, where the charge limit is very small.

Once a flammable refrigerant is on your premises, DSEAR applies regardless of layout. HSE lists duties including that employers must "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). A factory-sealed monoblock does not exempt you; it makes the assessment more predictable, because the charge, the location and the marking all arrive with the unit. Our post on R290 in commercial refrigeration goes deeper.

What happens when each one fails

This is the part of the comparison nobody reads until it matters. A monoblock is one thing, so when it fails beyond simple repair the fix is an exchange: off the wall, new one on. If the right unit is to hand the swap is quick; if it has to be ordered, the room is down until it arrives.

A split fails by component. A fan motor, a contactor, an expansion valve or a controller can each be replaced while the rest of the system stays put, which is kinder to budgets over a long life. The trade-off is more joints, so more potential leak points, and any repair that opens the circuit needs a certified engineer on site. Planned visits are where this gets caught early, which is the argument for planned refrigeration servicing.

Choosing between them for your room

A monoblock usually wins when the room is small to medium, stands against an outside wall or under a usable roof, and the site wants minimal building work and minimal refrigerant handling on the premises. A split usually wins when the room is large or heavily loaded, sits indoors with no ventilated space beside it, needs the heat out of the building altogether, or shares plant with other rooms.

Be wary of a supplier who only sells one layout; they will find reasons it fits your room. Ask where the heat goes, what the refrigerant is, and who is allowed to touch it, and the right answer usually shows itself.

When to talk to an installer

If the quotes for your new or replacement cold room mix monoblock and split layouts without explanation, get a survey rather than another brochure. Be Cool is a family-run London firm, trading since 2004, with F-Gas certified engineers and more than 2,000 projects across London and the South East. Talk to us about cold room installation before the panels are ordered, because the layout is far easier to change on paper than on site.

Frequently asked questions

Is a monoblock refrigeration unit powerful enough for a walk-in freezer?

Freezer-rated monoblocks exist for small and medium freezer rooms. One packaged unit can only move so much heat, so large freezer rooms and heavy loading call for a split with a properly sized remote condensing unit.

Does a monoblock need an F-Gas certified engineer to install it?

Physically mounting the unit and connecting power is building and electrical work. The qualification rules cover installing, servicing, leak checking and recovery on equipment containing F gas, with a category 4 certificate for leak checks that do not break into the circuit. Once anyone opens the circuit of a factory-charged unit, certified people only.

Which is cheaper to run, a monoblock or a split?

Siting decides it more than the badge on the unit. A monoblock rejecting heat into a hot, unventilated kitchen runs long hours against warm air; a split condensing unit in free air usually works against a lower condensing temperature. Our breakdown of commercial refrigeration energy costs shows where the money goes day to day.

What refrigerant will a new cold room unit use?

Not R404A on new stationary plant, because HFCs with a GWP of 2,500 or more have been banned from the GB market since 2020, and hermetically sealed commercial equipment at GWP 150 or more followed in 2022. Ask what the unit runs on: propane and lower-GWP options are available. Check the plate, and ask the supplier to confirm the GWP in writing.

Making the call before the panels arrive

Four things settle this: the size and duty of the room, where the heat can go, what refrigerant the rules allow, and who you want touching the system. If you are weighing quotes now, ask us for a quote and we will walk the site and tell you plainly which layout fits.

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: 16 October 2026