Ice is a symptom of moisture, not of cold
A sealed, dry freezer with a working defrost system stays essentially frost-free for months. Ice means two things are both true: humid air is getting into the box, and the defrost system is not clearing what that air leaves behind. Fixing only one of them gets you a few weeks before the ice is back.
Where the ice is, and what it means
On the evaporator coil
The normal place for frost to form and the place defrost exists to clear. Heavy, persistent ice here means defrost is failing: an open heater element, a dead termination sensor, a seized timer, or a cycle schedule that was never matched to how hard this box actually works. A coil that re-ices within a day of being cleared is a defrost fault, full stop.
Around the door, on the frame, on the ceiling near the entrance
Air infiltration. Warm humid kitchen air is entering and dumping its moisture the moment it crosses the threshold. Look at the gasket along its whole length, check whether the door actually pulls itself shut, and see whether the door heater wire around the frame is still working. If you can feel a draught or see daylight at any point, that is the source.
On the floor below the evaporator
The drain is not draining. Meltwater from each defrost cycle is running out of the pan onto the floor and freezing there. The drain line is blocked, frozen, or its heat trace has failed. This one gets dangerous — a sheet of ice on a freezer floor is a staff injury waiting to happen.
On product and packaging throughout the box
Chronic high humidity, which means chronic infiltration. Usually a door problem that has been tolerated for a long time, sometimes a panel joint that has opened up, occasionally a failed vapour barrier in the structure itself.
The infiltration sources nobody checks
- The pressure relief port. Every freezer has one to stop a vacuum forming when warm air cools. If its heater has failed it ices shut, and then the box fights you every time you open the door — or the port stays stuck open and leaks continuously.
- Panel joints. Walk-in panels lock together with cam fittings. Over years of thermal movement and the occasional pallet jack impact, joints open. You can usually find them by the frost line on the outside face.
- Conduit and pipe penetrations. Anywhere something was run into the box after installation and the hole was not properly sealed.
- The door sweep. The bottom seal takes the most abuse and is the most often missing entirely.
What it costs you to leave it
Ice is expensive in ways that do not show on a repair invoice. An iced coil cannot transfer heat, so the compressor runs longer for less cooling and your energy bill climbs quietly. Product develops freezer burn and gets thrown out as shrinkage. Staff lose time chipping ice. And eventually the box stops holding temperature altogether, which is when it becomes an emergency at the worst possible moment.
Our approach on this call
We clear the ice properly rather than chipping at it, then test every defrost heater element individually instead of assuming the bank is good, verify the termination sensor actually terminates, and check the drain line and its heat trace end to end. Then we walk the box looking for where the moisture is coming in, because clearing the ice without closing the source just books you another visit in six weeks.
Questions we get asked
Can I pour hot water on the ice to clear it?
No. The water refreezes somewhere worse, usually in the drain pan and the drain line, and you end up with a blocked drain on top of whatever you started with. Controlled defrost or a proper manual defrost with the box emptied is the only safe way.
How often should a freezer defrost?
Typically four to six times in 24 hours, with the cycle terminating on coil temperature rather than running its full time. Heavy door traffic needs more, a rarely opened storage freezer needs fewer. If yours is on a fixed schedule nobody has reviewed since installation, that is worth checking.
There is ice only on one end of the coil. Does that mean anything?
Yes, and it is one of the most useful clues there is. A consistently iced section with the rest clear points at an open defrost heater element in that part of the bank, or at a refrigerant distribution problem feeding that circuit poorly.