Knowledge Base

Everyone knows commercial refrigeration equipment gets more expensive to run as it ages. Fewer people can say where the money actually goes. It usually is not the compressor — it is the heat exchange surface. A layer of scale just one millimetre thick on a condenser or evaporator raises energy consumption by roughly 7% to 9%, according to the Refrigeration and Air Conditioning Engineering Handbook. One millimetre is about the thickness of a coin. It looks fine to the eye. The meter is already charging you for it.

Start with the condenser side. On air-cooled units, dust-clogged fins are the most common problem, especially in commercial kitchens and flour-processing rooms where both particulates and oil mist are heavy. Once the gaps between fins are blocked, airflow drops, condensing pressure climbs, compressor load follows, and on a hot day the unit will simply trip on high-pressure protection. The fix is not complicated: blow the fins through with compressed air once a month, working along the fin direction rather than straight into them. Perpendicular blasts flatten the fins and reduce the free area you were trying to recover. On water-cooled condensers, the water side matters more. Scale, algae and biological slime deposit on the tube walls, and the usual industry cadence is a cleaning every three to six months using a chemical descaler plus mechanical brushing. A water filter ahead of the inlet, with filters replaced on schedule, saves a lot of that work. There is a crude but reliable way to tell whether a condenser needs attention: watch the water temperature difference across it. A chiller running normally shows roughly 4 to 6 degrees Celsius. When that spread shrinks noticeably, heat transfer has already degraded.

Now the evaporator. On ice makers, slush machines and flake ice units, frost formation is normal operation — but thickness matters. Even frost up to about 5 millimetres is within range; beyond that, pay attention. Patchy, locally heavy frost usually points in one of two directions: insufficient refrigerant charge, or an expansion valve that is not opening correctly. A low-side pressure reference of 0.2 to 0.3 MPa is useful here; consistently lower readings generally confirm a charge shortfall or a restriction in the system. One fault class is particularly misleading: the machine keeps refrigerating, the water pump keeps circulating, the ice layer grows thicker and thicker, but the harvest cycle never triggers. That is usually a water-temperature probe problem — the control system cannot read the temperature correctly. A multimeter resistance check on the probe settles it quickly. For cleaning, wipe down the evaporator surface monthly, and weekly in areas that frost heavily.

It helps to turn all of this into a schedule. Daily or per shift: log the temperature difference across the medium, circulation flow, pump current and outlet pressure; listen for unusual vibration or noise; check medium level and colour. Monthly: blow down air-cooled fins, clean the evaporator surface, clear strainers, check water hardness. Quarterly: inspect electrical terminals for looseness and oxidation, measure running current and voltage, lubricate fan bearings, and verify temperature and pressure sensor accuracy — replace anything drifting more than 5%. Annually: leak-test the system, check refrigerant operating pressures, replace aged seals, and deep-clean the water circuit. Before any long winter shutdown, drain the water system completely or charge it with the correct proportion of glycol antifreeze. A frozen and split pipe is an expensive repair.

Refrigerant leaks deserve their own paragraph. Brazed joints, valve connections and seals are the three weak points. When inspecting, look for oil staining first — refrigeration oil migrates out with the leaking refrigerant, so an oil trace is often a signpost pointing at the leak. Electronic leak detectors are far more sensitive than soap solution, and a full system leak test at least once a year is worth the cost. By ASHRAE standards, an annual leak rate above 15% on refrigerants such as R404A is no longer a top-up situation; it calls for systematic repair and remediation. Fitting rubber isolation pads at vibration points to prevent joint fatigue cracking is the cheapest preventive measure available.

A few common mistakes are worth calling out, because almost every premature equipment failure traces back to one of them. Blasting fins with a high-pressure water jet looks effective but flattens them badly. Using a strong acid descaler without a proper neutralising rinse leaves residual acid eating into the tube walls. Reassembling without replacing seals starts a slow leak immediately. And working on live equipment — compressors and electrical components should never be serviced with power connected. This is a high-pressure system; refrigerant charging and control board repair are best handed to a qualified service provider.

Putting heat exchanger cleaning on a fixed schedule pays back visibly. Maintenance data from the sector shows that regular servicing extends unit life by three to five years, cuts failure rates by more than 40%, and delivers 15% to 30% in combined energy savings. That arithmetic is worth more attention than any single equipment quotation.