Phoenix Journal · Kitchens
A cold store rarely fails because the refrigeration is faulty - it fails because of where the plant sits, how it breathes and whether the coil is clean. Here are the layout basics that keep yours holding temperature.
Case postmortem
A busy site rang us on a Friday in August because the walk-in freezer had quietly crept up to -9°C overnight, and nobody could work out why.
The story is one we hear a few times every summer. The cold store had been running perfectly for three years. Then the kitchen was reworked - a new six-burner range and a char-grill went in along the back wall - and within a fortnight the freezer next door started struggling. The chef assumed a refrigerant fault and called an emergency engineer. The engineer found no leak, no failed compressor and no blocked evaporator. What he found was a condensing unit tucked into a hot corner, breathing in air that was already close to 40°C, choked with a felt of grease-laden dust across its coil. The refrigeration was fine. The layout around it was the problem.
Cold store and refrigeration layout is not really a refrigeration topic at all - it is a heat, air and access topic. Get the placement, clearances and cleaning schedule right and a plant runs quietly for years. Get them wrong and you spend money on call-outs, spoiled stock and shortened compressor life while blaming the kit. This is what went wrong on that site, and how the layout basics prevent it.
A refrigeration system does not make cold - it moves heat. The evaporator inside the cold store absorbs heat from the food and the fabric, and the condenser has to dump that heat somewhere else. If the condenser cannot reject heat, everything downstream fails: head pressure climbs, the compressor runs hot and long, and the box stops holding temperature. On this job three layout failures stacked up.
First, siting. The condensing unit sat within a metre of a new cooking line, pulling in air that the extraction canopy had not fully captured. A condenser rejecting heat into already-hot air is like a radiator in a sauna - the temperature difference it relies on has collapsed. Every degree of extra intake air temperature makes the compressor work harder for the same result.
Second, clearance and airflow. The unit had been shoehorned against a wall with barely a hand's width around it, so its own warm discharge air was being drawn straight back into the intake. That short-circuit of hot air is one of the most common causes of a system that "cools fine in winter but dies in summer".
Third, and the one closest to our world, was fouling. The coil was blanketed in the greasy dust that drifts off any cooking line. A clogged condenser coil acts like a blocked radiator: airflow drops, heat rejection drops, and the compressor pays for it. None of this showed up as a refrigeration fault because none of it was one. It was a layout and housekeeping failure that only surfaced when the surrounding heat load changed.
The numbers that matter
Those first two figures set the target the layout has to hit reliably, day in and day out, including the hottest week of the year. Under the Food Standards Agency rules the 8°C limit applies to the temperature of the food itself, not just the air, which is why chefs are expected to record temperatures at least twice a day per unit. The F-Gas figure is a reminder that once your system holds a meaningful refrigerant charge it falls under a legal maintenance regime - leak checks every twelve months for 5 to 50 tonnes CO₂e, every six months up to 500 tonnes, with records kept for five years and all work done by an F-Gas certified engineer.
We fixed the immediate problem in an afternoon and the underlying one over the following month. If you are planning a cold store, or trying to work out why an existing one is struggling, these are the layout basics that keep a plant honest.
On our Friday call-out the coil clean alone brought head pressure back down and pulled the freezer to temperature within a few hours. The lasting fix was relocating the condensing unit away from the new cooking line and putting a quarterly coil clean into the deep clean rota so the fouling never builds to that point again.
Placement solves the heat problem, but only if the store itself is sized and sited sensibly for the volume of stock and the traffic through the door. An undersized box with a door that never stops opening will fight its own layout no matter how well the condenser is placed. If you are at the planning stage, our guide to walk-in cold room sizing, siting and running costs works through the decisions that sit alongside everything above, so the fabric, the plant and the daily use all pull in the same direction.
Questions
Almost always it is a heat rejection problem, not a refrigeration fault. In warm weather the condenser has to reject heat into hotter intake air, so any weakness in siting, clearance or coil cleanliness shows up. If the unit sits near a cooking line, is tight against a wall so its own warm air recirculates, or has a coil blanketed in greasy dust, it will hold temperature in winter and lose the battle in summer.
For chilled food the legal maximum in England, Wales and Northern Ireland is 8°C, and most kitchens aim for 0-5°C in practice. Frozen storage should be at -18°C or colder. The 8°C limit applies to the temperature of the food itself, so you should record temperatures at least twice a day per unit.
It depends on the refrigerant charge measured in tonnes of CO₂ equivalent. Systems of 5 to under 50 tonnes CO₂e need a check at least every 12 months, 50 to under 500 tonnes every six months, and 500 tonnes or more every three months. A fitted automatic leak detection system can double those intervals. Records must be kept for five years and the work must be done by an F-Gas certified engineer.
Phoenix Duct Clean · by the numbers
Great equipment still needs a clean kitchen around it. Phoenix deep-cleans commercial kitchens to the standard an inspection scores - UK-wide, around your service.