A hotel kitchen manager in Kensington called us worried about his electricity bill. It had jumped 40% over three months and he couldn’t figure out why. We found the answer in the basement — his walk-in cold room compressor hadn’t cycled off in weeks. It was running 24/7, pulling the temperature down to 1°C, then fighting against heat ingress that was overwhelming the system’s capacity. The cold room was maintaining temperature, just barely, but the compressor was doing double the work it should have been.
The cause? The door seal gasket had degraded along the bottom edge. You couldn’t see it unless you got down on the floor with a torch, but warm kitchen air was streaming in under the door every time it closed. A £150 gasket replacement solved a problem that was costing them £400 a month in excess electricity.
Why a Compressor Should Cycle
A properly functioning cold room compressor should cycle on and off throughout the day. It runs until the cold room reaches set point temperature, then the thermostat switches it off. As the temperature gradually rises from door openings, product loading, and ambient heat gain, the thermostat eventually calls for cooling again and the compressor starts. A typical well-sealed cold room might see the compressor run 40-60% of the time. If it’s running continuously, the system is losing more heat than it can remove — and something is wrong.
Common Causes
Door Seal Failure
The most common cause and the cheapest to fix. Door gaskets wear with use — they compress, crack, and lose their seal. On busy cold rooms where the door is opened 50+ times a day, gaskets can degrade within 12-18 months. Check by closing the door on a piece of paper — if you can pull the paper out easily, the seal isn’t sealing.
Evaporator Coil Icing
If the defrost cycle isn’t functioning correctly, ice builds up on the evaporator coil and blocks airflow. The compressor runs longer trying to compensate for reduced cooling capacity. Eventually the coil ices up completely and cooling stops altogether. Check by opening the cold room and looking at the evaporator — if it’s covered in ice or frost, the defrost system needs attention.
Low Refrigerant Charge
A slow leak reduces the system’s cooling capacity. The compressor runs longer and longer to maintain temperature. It’s insidious because the system still works — just less efficiently. By the time the compressor runs constantly, the system may have lost 30-40% of its charge. This needs an F-Gas engineer to leak test, repair, and recharge.
Dirty Condenser
Same story as always. A blocked condenser can’t reject heat, so the system’s cooling capacity drops. The compressor compensates by running longer. Eventually it can’t keep up.
What to Check
- Door seals — do the paper test on all four sides
- Evaporator coil — any visible ice buildup?
- Condenser — is it clean and is the fan running?
- Door closer — is the door actually closing fully every time?
- Strip curtain — if fitted, is it intact or are strips missing?
If the seals, coils, and condenser look fine, the problem is likely refrigerant charge, thermostat calibration, or an undersized system that can’t cope with the actual heat load. Call 020 3974 1419 and we’ll diagnose the issue properly.