--- title: "Why the evaporator ices over, and what the ice pattern reveals" description: "Frost that clears in a defrost cycle is routine; ice that stays points to airflow, a cold exhaust room or a low charge, and how far it climbs the coil helps say…" url: "https://winecellarrepair.center/guides/why-the-evaporator-ices-over/" date_modified: "2026-09-26" --- Common problems # Why the evaporator ices over, and what the ice pattern reveals A wine cellar cooling unit freezing up is usually starved of air across the cellar-side coil, running with an exhaust room colder than the maker allows, or short of refrigerant. Thaw the coil with the power off, then check the grille, the filter and the fan. Ice that covers only the lower part of the coil and returns within days points to the refrigerant side. By [WineCellarRepair.center technical team](https://winecellarrepair.center/authors/technical-team/) Published September 26, 2026 ## At a glance. A little frost on a cellar coil is part of ordinary running. A wine cellar cooling unit freezing up is something else: a white block behind the grille, a weaker draft of air, and water on the floor once the ice lets go. Read the whole guide ### When WhisperKool starts an anti-frost cycle Coil at 26°F for five minutes The compressor rests until the coil reaches 40°F or ten minutes pass. ### CellarPro's factory defrost Every 16 hours, for 20 minutes On units with its remote display; a manual defrost starts after 3 seconds on the key. ### Exhaust room that is too cold Below 50°F CellarCool names it as a cause of ice on its through-the-wall CX series. ### Ice only part way up the coil A possible low charge WhisperKool and CellarCool both read that pattern as a refrigerant question. In this guide 1. Frost that comes and goes, ice that stays 2. Airflow is the first thing to rule out 3. When the exhaust room is too cold 4. Reading the pattern: airflow or refrigerant 5. Thawing the coil without soaking the cellar 6. Questions ## Frost that comes and goes, ice that stays The coil behind the cellar-side grille runs below freezing for part of each cycle, so a thin frost is expected, and controllers clear it on a schedule or by a sensor. CellarPro's remote display runs a 20-minute defrost every 16 hours with the evaporator fan on. WhisperKool's SC series watches a coil probe instead and stops the compressor once the coil has sat at 26°F for five minutes, letting the fans clear it until it reaches 40°F. Ice is the frost those cycles failed to remove. It bridges the gaps between fins, chokes the airflow, and then grows faster, because less cellar air reaches the metal to warm it. The cellar warms while the unit sounds busier than ever, so plenty of owners learn about it only when the unit is switched off for some reason and a sheet of meltwater follows. - A dull white film that vanishes within an hour of the compressor stopping: normal. - Solid ice you cannot see through between the fins: not normal. - Water in the tray frozen into a slab: the drain and the coil together. - A defrost symbol lit for most of the day: the controller is losing ground. Source: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) — Anti-frost starts when the coil probe reads 26°F for five minutes and ends at 40°F or ten minutes; ice causes are a dirty coil, blocked airflow and a stopped evaporator fan; clean the coil by vacuum or weak detergent spray flushed after 5 minutes; for the Ad3 alarm make sure intake air is not below 60°F; ice part way up the coil can mean low refrigerant, all the way up a dirty coil or blocked air; holding the up arrow about five seconds starts anti-frost only below 40°F; [CellarPro — 1800 series owner's manual](https://www.cellarprocoolingsystems.com/PDF%20Documents/Owners%20Manual%201800.pdf) — Remote display units defrost every 16 hours for 20 minutes, manual defrost by holding the key 3 seconds; 3 inches clear in front and 8 inches below the cold air discharge, free of bottles and racks; optional air filter replaced every 3 to 9 months; raise the minimum set point to 58°F or above when dripping ## Airflow is the first thing to rule out The cellar-side coil needs a steady stream of room air to stay above freezing, and anything that thins that stream drives the coil colder. The troubleshooting tables for WhisperKool's and CellarCool's through-the-wall units open with the same three airflow causes: a dirty coil, something blocking the supply or return air, and an evaporator fan that has stopped. ### Racks, cases and bottles in front of the grille CellarPro wants a minimum of 3 inches free before the face of its 1800 units and 8 inches below the cold air discharge, with no bottles or racking in that space. A case parked on top of a rack, a new run of racking fitted close under the unit, or a decorative panel placed over the grille can halve the airflow without anyone noticing the change. ### A dusty coil or a clogged filter Cellars collect cardboard dust and fine lint from wooden racking, and it settles on the cellar-side coil. WhisperKool's instruction is to vacuum that coil and, when it is very dirty, mist it with a weak dish detergent solution, wait five minutes and flush with fresh water. Do it only with the unit unplugged, and only on the coil face you can reach through the grille. Units with an intake filter need it changed on schedule; CellarPro quotes 3 to 9 months for its optional rear filter depending on conditions. ### An evaporator fan that has stopped Hold a hand near the cellar-side grille while the compressor runs and you should feel a steady draft of cold air. If the compressor hums and the fan on that side is still, the coil freezes solid within hours. WhisperKool sends that case straight to a technician, since the motor, its capacitor or the controller output can each be responsible. Source: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) — Anti-frost starts when the coil probe reads 26°F for five minutes and ends at 40°F or ten minutes; ice causes are a dirty coil, blocked airflow and a stopped evaporator fan; clean the coil by vacuum or weak detergent spray flushed after 5 minutes; for the Ad3 alarm make sure intake air is not below 60°F; ice part way up the coil can mean low refrigerant, all the way up a dirty coil or blocked air; holding the up arrow about five seconds starts anti-frost only below 40°F; [CellarCool — CX series owner's manual](https://www.cellarcool.com/wp-content/uploads/2021/10/CC-CX_Series-OM-061219.pdf) — Ice forms when the coil is dirty, air is blocked, the evaporator fan is off, or the exhaust room drops below 50°F; ice only part way up the coil face may mean low refrigerant Close on thin frost across the aluminum fins of a split-system evaporator coil mounted high in a wine cellar. ## When the exhaust room is too cold Icing is a winter complaint as often as a summer one. A through-the-wall unit relies on the air at its exhaust side to keep refrigerant pressure up; when that air turns cold, pressure falls and the cellar coil drops further below freezing. CellarCool names an exhaust room below 50°F as a cause of ice on its CX series, and WhisperKool's defrost alarm instructions ask owners to make sure the intake air is not below 60°F. Unheated garages, northern basements and exterior walls in January are where this shows up. Split systems handle cold outdoor air with low-ambient controls, and Wine-Mate tells buyers to add a low-ambient kit to its split condensing units where the installation area drops below 50°F. If the icing began with the first cold week, the answer may be heat in the exhaust space or a low-ambient kit rather than a repair. Source: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) — Anti-frost starts when the coil probe reads 26°F for five minutes and ends at 40°F or ten minutes; ice causes are a dirty coil, blocked airflow and a stopped evaporator fan; clean the coil by vacuum or weak detergent spray flushed after 5 minutes; for the Ad3 alarm make sure intake air is not below 60°F; ice part way up the coil can mean low refrigerant, all the way up a dirty coil or blocked air; holding the up arrow about five seconds starts anti-frost only below 40°F; [CellarCool — CX series owner's manual](https://www.cellarcool.com/wp-content/uploads/2021/10/CC-CX_Series-OM-061219.pdf) — Ice forms when the coil is dirty, air is blocked, the evaporator fan is off, or the exhaust room drops below 50°F; ice only part way up the coil face may mean low refrigerant; [Wine-Mate (Vinotemp) — WM-2500 to 6500 SSR split system owner's manual](https://cdn.shopify.com/s/files/1/0555/0676/3891/t/7/assets/description_image_wm2500_6500ssr_owners_manual.pdf?v=1643942351) — If the installation area will be below 50°F, purchase a low ambient condition kit ## Reading the pattern: airflow or refrigerant After a thaw, watch where the ice forms again. WhisperKool and CellarCool give the same rule of thumb: ice that climbs the whole face of the coil points to dirt or blocked air, while ice that stops part way up suggests the unit is low on refrigerant. With a short charge only the first rows of tubing get cold enough to freeze, and the rest of the coil runs warm. A shortage means a leak, because a sealed circuit does not use its refrigerant up. Finding the leak, repairing it and recharging to the maker's weight is work for a refrigeration technician holding EPA Section 608 certification, and on a split system that includes testing the line set between the two rooms. - Ice across the full face, fan turning, filter clean: recheck what sits in front of the grille and how clean the fins are. - Ice on the lower rows only, back after each thaw: a refrigerant question. - Ice only in the coldest months: the exhaust room temperature. - Ice together with a defrost alarm on the display: write the code down before resetting anything. Source: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) — Anti-frost starts when the coil probe reads 26°F for five minutes and ends at 40°F or ten minutes; ice causes are a dirty coil, blocked airflow and a stopped evaporator fan; clean the coil by vacuum or weak detergent spray flushed after 5 minutes; for the Ad3 alarm make sure intake air is not below 60°F; ice part way up the coil can mean low refrigerant, all the way up a dirty coil or blocked air; holding the up arrow about five seconds starts anti-frost only below 40°F; [CellarCool — CX series owner's manual](https://www.cellarcool.com/wp-content/uploads/2021/10/CC-CX_Series-OM-061219.pdf) — Ice forms when the coil is dirty, air is blocked, the evaporator fan is off, or the exhaust room drops below 50°F; ice only part way up the coil face may mean low refrigerant; [US EPA — Section 608 technician certification](https://www.epa.gov/section608/section-608-technician-certification-0) — Technicians who service equipment that could release refrigerant are certified under Section 608 of the Clean Air Act ## Thawing the coil without soaking the cellar Unplug the unit, lay towels under the cellar-side grille and the drain port, and let the coil thaw by itself; a fan blowing room air at the grille speeds it up. The makers mention warming a stubborn coil with a hair drier, but with meltwater running close to the unit's own cord a fan is the safer tool. Restart only when the fins look clear, and check that the tray and the drain line are running before the first full cycle. WhisperKool's SC controller also lets an owner start an anti-frost cycle by holding the up arrow for about five seconds, but only while the coil is below 40°F; above that the display blinks three times and carries on. That clears light frost. It will not shift a solid block, and repeating it on an iced coil only delays finding the cause. Source: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) — Anti-frost starts when the coil probe reads 26°F for five minutes and ends at 40°F or ten minutes; ice causes are a dirty coil, blocked airflow and a stopped evaporator fan; clean the coil by vacuum or weak detergent spray flushed after 5 minutes; for the Ad3 alarm make sure intake air is not below 60°F; ice part way up the coil can mean low refrigerant, all the way up a dirty coil or blocked air; holding the up arrow about five seconds starts anti-frost only below 40°F ## Where to stop Call for a visit if ice returns within a few days of a full thaw with the grille clear and the fan turning, if it forms only across the lower part of the coil, or if the controller shows a defrost alarm that comes back after a restart. Those lead to the refrigerant charge, the defrost sensor or the fan circuit. Never pry or scrape ice from the fins with anything metal: a punctured coil turns an icing problem into a refrigerant leak. Written by [WineCellarRepair.center technical team](https://winecellarrepair.center/authors/technical-team/). Cellar cooling technicians who write from readings taken in the room, at the exhaust side and along the line set. Sources: [WhisperKool — SC Pro series owner's manual](https://whisperkool.com/wp-content/uploads/2022/12/WK-SC-Series-OM-22-w-UV-120122.pdf) · [CellarPro — 1800 series owner's manual](https://www.cellarprocoolingsystems.com/PDF%20Documents/Owners%20Manual%201800.pdf) · [CellarCool — CX series owner's manual](https://www.cellarcool.com/wp-content/uploads/2021/10/CC-CX_Series-OM-061219.pdf) · [Wine-Mate (Vinotemp) — WM-2500 to 6500 SSR split system owner's manual](https://cdn.shopify.com/s/files/1/0555/0676/3891/t/7/assets/description_image_wm2500_6500ssr_owners_manual.pdf?v=1643942351) · [US EPA — Section 608 technician certification](https://www.epa.gov/section608/section-608-technician-certification-0) For the heart of your home. ## Questions owners ask. ### Can I leave the unit off for a day to melt the ice? A few hours with the power off is usually enough, and it does the wine no harm if the door stays shut, since a well-built cellar warms slowly. A whole day off only makes sense if the meltwater is being caught and the cause will be found before the restart. ### Does a colder setting make icing worse? It can. A lower set point keeps the compressor running longer and the coil colder, which is why CellarPro suggests a minimum set point of 58°F or above when its units drip. Stay near the maker's recommended setting rather than chasing a colder cellar. ### Is icing on a split system any different? The coil behaves the same, but more parts can cause it: the outdoor unit's low-ambient control, the length and insulation of the line set, and the metering device at the evaporator. A split system that keeps icing needs its pressures read at both ends. ### Why did the ice appear right after new racking went in? New racking often sits closer to the unit or under its cold air discharge, which cuts the airflow over the coil. Check the clearances in your manual and move the nearest bottles before suspecting a part. ## The problems behind it. Each has a page of its own: what it usually means and the causes in the order worth checking. [All 17 problems](https://winecellarrepair.center/problems/) Problem ### Cellar Cooling Evaporator Coil Icing Up 5 causes, cheapest first The collection is exposed ### Cellar Cooling Unit Leaking Water 6 causes, cheapest first The collection is exposed ### Wine Cellar Too Warm 6 causes, cheapest first Problem ### Cellar Cooling Unit Fan Not Running 4 causes, cheapest first ## When it needs a technician. The repairs on the right are where this guide ends when the checks do not settle it. ### Cellar coil icing and defrost repair Stopping ice from forming on the cellar coil by finding what starves it, whether airflow, charge, controls or humid air coming into the room. ### Cellar evaporator and condenser fan repair Restoring the two fans a cellar unit depends on: the one that moves cellar air across the cold coil and the one that throws the heat away. ### Cellar cooling leak search and recharge Finding where a cellar unit or a split system is losing its refrigerant, repairing the joint or coil, and charging it by weight rather than topping it off. ### Split-system cellar line set repair Repairing, reinsulating or rerunning the copper lines and control cable that join the cellar evaporator to its outdoor or remote condensing unit. ## More in common problems. What it means when the cellar will not come down to 55°F, water runs down the wall below the unit, the evaporator turns white with ice, or the cooling never seems to rest. [The whole section](https://winecellarrepair.center/guides/common-problems/) What the room and the unit are telling you ### Why the cellar will not hold 55°F: the room, the exhaust side or the unit A quick air test at both grilles shows whether the unit is cooling at all; after that the exhaust room, the door, the vapor barrier and the unit's size each tell their own story. What the room and the unit are telling you ### Why the cellar unit drips water, and which side of the wall it lands on Water on the cellar floor, down the exhaust-side wall or from a ceiling unit points to different parts of the drain path, and much of it starts with humid air leaking into the room. Guides ### All 18 guides Six sections, by what you are trying to find out. --- **[Read on the site: Why the evaporator ices over, and what the ice pattern reveals](https://winecellarrepair.center/guides/why-the-evaporator-ices-over/)** **[Book a visit with WineCellarRepair.center](https://winecellarrepair.center/schedule/)**