The machine is making ice, the bin is filling, and yet the day's output is short. When a buyer sends us that complaint, the first thing we time is the harvest: the few minutes when hot refrigerant gas is diverted into the evaporator so the frozen slab releases and drops. If that stage is stretched, the machine is running, drawing power and producing nothing — the most expensive state an ice machine can be in, and the easiest to miss because the fault code is silent.

The principle: harvest is a controlled thaw

During freezing, water is pumped over a nickel-plated copper mould and the growing ice grips the metal. To release it, the controller stops the pump, closes the water inlet and opens the harvest solenoid so hot discharge gas flows directly into the evaporator. The plate warms a few degrees, the bond between ice and metal breaks, the slab slides onto the grid, breaks into cubes, and the falling ice trips the curtain switch to restart freezing. If the gas is not hot enough, not flowing enough, or the ice is too thick, release slows and every cycle loses seconds. Over a day of roughly 15 to 20 minute cycles, those seconds accumulate into lost tonnage.

Where the time goes

What the specification tells you, and what it does not

Our listings publish the freeze cycle as 15 to 20 minutes per batch on the smaller and mid-range cube machines, the ice size as 22 x 22 x 22 mm on the standard models, and the condenser type as copper fin with a copper-plated nickel ice mould. What no catalogue states is the harvest duration for your site, because it depends on ambient and head pressure. Ask for the expected harvest time for the model you are buying and record your own at commissioning — that baseline is what makes a slow harvest detectable two years later.

The choice of refrigerant also matters here. Models in our range are supplied on R404a, R507a, R134a or R22 depending on capacity and market, and the harvest behaviour differs with the pressure the system reaches: a machine running at low head pressure in a cold room has less hot gas available, which is why winter complaints and cold-store installations show up together.

Six checks in the right order

1. Time one complete harvest. From the moment the valve opens to the moment the last cube drops. Write it down with the ambient temperature beside it.
2. Weigh ten cubes. If they are heavier than the ice size implies, the freeze is running too long and the slab is mechanically harder to release.
3. Watch the release pattern. Simultaneous release across the whole plate is normal. Corners hanging on means scale or a worn surface, not a gas problem.
4. Measure pressures at harvest. A healthy system shows a rapid rise in the hot gas line; a cool line after thirty seconds points upstream to the valve or the charge.
5. Test the curtain switch. A sticking curtain ends the cycle late and disguises itself as a slow harvest.
6. Check the room. In a cold room or in winter, head pressure control or fan cycling may be needed to keep harvest working.

Fixes, from cheapest to most serious

• Reset the ice thickness to the standard for the model and re-timer the harvest.
• Clean and descale the mould and the water curtain. A chalky surface is a mechanical brake on release.
• Replace a failed solenoid coil or a blocked strainer — a low-cost part with a large output effect.
• Leak test and recharge to the specified weight; never top up on guesswork.
• If the compressor no longer reaches pressure at harvest, evaluate replacement rather than adding refrigerant repeatedly.

FAQ

How long should a harvest take? It should be a small fraction of the published 15 to 20 minute cycle. Ask for the figure for your model and record your own at commissioning.

Can a slow harvest damage the compressor? Indirectly. Long harvests mean long low-load running and repeated hot gas cycling; the compressor runs outside its efficient envelope.

Is a thicker cube better for drinks? It melts more slowly, but it also lengthens every cycle and raises energy per kilogram. Standard 22 x 22 x 22 mm cubes suit bar service well.

Why does it only happen in winter? Low ambient means low head pressure; without control, there is not enough hot gas to release the slab quickly.

If your harvest now takes noticeably longer than it did at commissioning, the machine is losing output every hour. Send us the model, the ambient temperature and your timed harvest, and we will narrow it down. See the 500–1000 kg/24h range, the 90 kg/24h bar machine, the 900 kg/24h BMC2000P, or ask our service engineers.