You walk into the cold room first thing in the morning and something’s off. The air doesn’t hit you like it should. You check the controller — 11°C. Should be 2°C. The dairy’s warm, the meat’s soft, and you’ve got a full day of service ahead.
We get this call two or three times a week across London, and the first 30 minutes matter more than people realise. Everything from here is about how fast you act.
Why 30 Minutes Matters
Food stored above 8°C enters the danger zone for bacterial growth. Your EHO inspector doesn’t care why the temperature went up — they care that it did and what you did about it. If you can get the fault identified and the cold room pulling back down to temp quickly, you might save the stock. Leave it four hours and you’re looking at a full write-off and an uncomfortable conversation with your food safety auditor.
Log the temperature immediately. Check your HACCP records. If the stock has been above 8°C for an extended period, it needs assessing — and in many cases, binning. It’s painful, but it’s less painful than a food poisoning incident and the rating drop that follows.
What’s Causing It
Condenser Coils Clogged
We’d put money on this being the fault before we even walk through the door. The condenser — whether it’s on the roof, on a wall bracket outside, or in a plant room — rejects heat from the system. In a kitchen environment, grease vapour, flour dust, and general airborne gunk coat those coils fast.
When the condenser can’t breathe, the whole system struggles. Head pressure rises, the compressor runs flat out, and the cold room can’t maintain its set point. We’ve attended sites where the remote condenser hadn’t been cleaned in two years. Completely furred up. The compressor was running at 110% and the cold room was sitting at 12°C on a mild day. On a hot day, it would have tripped out entirely.
Condenser cleaning is a ten-minute job during a routine service visit. When it’s left until the system fails, it becomes an emergency callout.
Low Refrigerant
If the cold room has been gradually losing performance over days or weeks — holding 4°C last month, 6°C last week, 9°C this morning — the charge is almost certainly leaking out somewhere. The system’s designed to operate with a specific weight of refrigerant. As it drops, cooling capacity drops with it.
Common leak points on walk-in systems: brazed joints on the pipework, Schrader valve cores, the compressor shaft seal on semi-hermetic units, and anywhere vibration has been working on a pipe for years. Under F-Gas regs, we locate and repair the leak before recharging. No exceptions.
Evaporator Icing Up
Open the cold room door and look at the evaporator coil (the unit with the fans mounted high up on the wall). If it’s covered in a thick layer of ice, there’s your problem. The ice insulates the coil and blocks airflow, so even though the system’s running, it can’t transfer heat out of the room.
Icing happens for a few reasons: the defrost timer has failed or is set wrong, the defrost heaters have burned out, or the system’s low on gas (which drops the evaporator temperature below the icing threshold). Some operators try to speed things up with hot water or a heat gun — don’t. You’ll damage the coil fins. Switch off the system, open the doors, and let it defrost naturally. Then call us to fix the underlying cause.
Door Seal Failure
Walk-in cold room doors take a hammering. Kitchen porters going in and out with trays, trolleys banging the frame, years of thermal cycling causing the gasket to harden and crack. Once the seal is compromised, warm, humid kitchen air leaks in constantly.
The telltale sign is ice build-up around the inside of the door frame. That’s moisture from the warm air freezing on contact with the cold surfaces. The compressor runs harder to compensate, energy bills climb, and eventually the system just can’t keep up.
Check the seal by closing the door on a piece of paper. If you can pull the paper out easily, the seal isn’t doing its job.
Fan Motor Failure
Walk-ins typically have two or three evaporator fans. If one fails, you might not notice immediately — the cold room still works, just less effectively. Temperature becomes uneven: cold near the working fans, warmer in the far corners. Product near the back of the room starts reading higher than the controller display would suggest.
This is why we tell clients not to rely solely on the controller reading. That sensor is in one position. The temperature three metres away could be completely different when a fan’s down.
Overloading
This one’s not a fault — it’s operational. If you’ve just taken a large delivery and loaded 200kg of ambient-temperature product into the cold room at once, the system has to work much harder to pull all that thermal mass down to temp. On a hot day, a fully loaded walk-in might take hours to recover.
Best practice: stage your deliveries. Don’t load everything in at once. And if possible, pre-cool product in a separate area before transferring it to the walk-in.
What You Can Check Before We Arrive
- Controller display — what temperature is it reading? Any error codes or alarm indicators?
- Evaporator coil — iced up, or clear with fans running?
- Door seal — any visible damage, ice around the frame, light coming through gaps?
- Condenser (if accessible) — can you see daylight through the coil, or is it blocked?
- Has anything changed recently? New equipment nearby generating heat? Door propped open during a busy service?
Keep the Door Shut
It sounds obvious but it’s worth saying: every time the door opens, warm air rushes in. While you’re waiting for the engineer, keep the door closed as much as possible. If the system is still running (just not holding temp), keeping the door shut gives it the best chance of at least limiting the damage.
Don’t Wait for It to Get Worse
A walk-in that’s struggling at 8°C today will be at 15°C tomorrow if the underlying fault isn’t fixed. And that’s when you start losing stock.
Call us on 020 3974 1419 for same-day cold room repair across London. We work on all makes — Foster, Williams, Hoshizaki, Hubbard, Dawsongroup, bespoke panel builds — and we carry refrigerant, common parts, and leak detection equipment on every van.