The parts of a cold room refrigeration system
- Compressor: the pump that circulates refrigerant and does the work. Scroll and reciprocating compressors are common; inverter-driven compressors vary their speed to match the load.
- Condenser: the coil and fan that reject heat to the outside air. It needs clear airflow and a cool spot; a condenser in a hot, enclosed yard makes the whole system work harder.
- Evaporator (cooler): the coil and fans inside the room that absorb heat from the air. Positioned so cold air sweeps the room without blowing straight on the door or the product.
- Expansion valve, pipework and refrigerant: the circuit that moves heat from inside to outside.
- Controller: the digital control panel that sets the temperature, runs defrost cycles, controls fans and raises alarms.
Monoblock or split system?
A monoblock (also called a packaged or wall-mounted unit) is factory charged and tested, so installation is quick: cut an opening, mount the unit, connect the power. It suits chilled rooms up to roughly 15 to 20 m³ and small freezer rooms, where the condenser can sit outside the room in a ventilated space. Its limits are capacity, the heat and noise it puts into the room next door, and the need for that outside space to be close.
A split system separates the condensing unit from the evaporator, so the noisy, hot part can go on a roof, in a rear yard or in a plant room up to tens of metres away. It scales to any room size, runs more quietly inside, and can serve several evaporators in large rooms. It costs more to install because of the pipework, the refrigerant charge on site and the electrical work, and it must be installed and commissioned by F-Gas certified engineers.
How a unit is sized
Refrigeration capacity is measured in kilowatts of cooling, and an engineer calculates it from the heat load the room has to remove: heat passing through the walls, ceiling and floor (so panel thickness matters), heat from warm product put into the room and how fast it must be pulled down, heat from the air that enters each time the door opens, and heat from lights, fans and people. A room that takes a pallet of warm product every afternoon needs a much larger unit than one that holds the same product already chilled. Undersized units run constantly and never quite reach temperature; oversized units short-cycle, which wears the compressor and controls humidity badly. The survey is where this is worked out.
Medium temperature and low temperature
Chilled rooms at 0 to +4 °C use medium-temperature units and can usually defrost on the off cycle, letting the room air melt frost between runs. Freezer rooms at -18 to -22 °C use low-temperature units with electric defrost heaters in the evaporator, a heated drain and a heated door frame. A low-temperature system has to move heat across a bigger difference, so it uses more energy per kilowatt of cooling and costs more.
Controllers and control panels
The controller is the small digital panel by the door. It sets the room temperature, starts and stops the compressor, times the defrost cycles, controls the evaporator fans and the door heater, and shows alarms for high temperature, door open and sensor faults. Good controllers log temperature and can connect to a remote monitoring service that sends alarms to a phone, which is the cheapest insurance a food business can buy. If your controller shows a fault code, note it before calling for a repair.
Refrigerants and the F-Gas Regulations
Many older cold rooms run on R404A, a refrigerant with a very high global warming potential that is being phased down under the UK F-Gas Regulations: it can no longer be used in most new equipment, and virgin R404A for servicing is restricted, so topping up a leaking R404A system is getting harder and dearer. New units use lower-GWP refrigerants such as R448A and R449A, or propane (R290) in sealed monoblocks, and large supermarket systems increasingly use CO2. Refrigerant may only be handled by F-Gas certified engineers, and systems above 5 tonnes of CO2 equivalent need recorded leak checks. If you are replacing a unit, this is the moment to move off R404A.
Energy: inverters, heat recovery and condenser placement
An inverter compressor matches its speed to the load instead of switching on and off, which saves energy and holds temperature more steadily. Heat recovery takes the heat the condenser would waste and uses it for hot water or space heating. Electronically commutated (EC) fan motors use less power than older types. The cheapest saving of all is placing the condenser where it has cool, free-flowing air and keeping it clean.
Signs a unit is failing
- The room will not reach temperature, or takes far longer than it used to.
- The compressor runs constantly, or starts and stops every few minutes.
- Ice builds on the evaporator between defrosts, or water drips inside the room.
- New noises from the fans or compressor, or oil stains near pipe joints (a sign of a refrigerant leak).
- Electricity bills rising without a change in use.
Repair or replace?
Fans, controllers, sensors, heaters, contactors and gaskets are repairs worth making at any age. A compressor failure on a unit under ten years old is usually worth repairing; on a unit over ten to fifteen years old, or one running on R404A, a new unit is often the better value once energy and future repairs are counted. We give you the choice with a fixed price for each. See commercial fridge and cold room repair.
Getting the right unit
Tell us the room size, what you store, how much goes in warm each day and where the condenser could go. We size the unit from the heat load and quote a monoblock or a split system with the make, model and capacity written down. Request a free quote, or read about cold rooms and freezer rooms.