Walk-in freezers
A freezer is not just a colder cooler. It has a harder job, a bigger load for its size, and a defrost problem that never goes away. Here is what that means for the box you are running.
Why a freezer is the harder machine
A cooler holds around +2 °C. A freezer holds −18 to −23 °C. That bigger gap between inside and outside drives more heat through every wall, every hour, forever. For the same box size, a freezer carries roughly twice the cooling load of a cooler.
It is also working against physics in a way a cooler is not. Every time the door opens, humid room air comes in and that moisture freezes onto the coldest surface it finds — which is the evaporator coil. A cooler sheds that moisture as water down a drain. A freezer turns it into ice.
That is the whole reason freezers have a defrost cycle, and the reason most freezer faults are ultimately defrost faults.
What defrost actually does
Several times a day the system deliberately stops cooling and warms the evaporator coil — usually with electric heaters built into it — until the ice melts off and runs out through a heated drain line.
Three things have to work for that to succeed:
- It has to start. A timer or controller initiates it on schedule.
- It has to get warm enough. Failed heater elements leave ice behind.
- It has to drain. The meltwater must leave the box through a line that is itself heated, or it refreezes in the drain and backs up.
When any one fails, the ice does not fully clear. The next cycle starts with more ice than the last. Within days the coil is a solid block, airflow stops, and the box warms up while the compressor runs flat out.
That is why ice on a freezer coil is urgent even while the temperature still looks fine.
Sizing a freezer?
Freezer loads run far higher per square foot than cooler loads. Get a sense of the capacity range before you talk to a supplier.
Switch the tool to freezer and compare it against the cooler figure for the same box — the difference is the point.
Where the ice is tells you something
Before anyone opens a panel, where the ice has formed narrows it down considerably.
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On the evaporator coil
The classic defrost fault — timer, heater element or termination sensor. Also a refrigerant or airflow problem making the coil run colder than it should.
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On the ceiling and walls
Moist air is getting in and staying. Usually a door seal, a failed closer, or a vapour barrier that has been breached somewhere in the panel work.
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On the floor, around the door
Door seal and sweep, or an underfloor heater that has failed. Ice at a doorway is a slip and trip hazard before it is anything else.
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Under the evaporator
Meltwater is not leaving. A frozen or blocked drain line, or a drain heater that has stopped working.
The door is half the battle
On a freezer, door hardware is not a cosmetic issue. Every second it is open you are paying to re-freeze the moisture that walked in.
Things worth checking, and worth fixing the week they appear rather than the month after:
- Gaskets torn, flattened or no longer touching all the way round
- A closer that no longer pulls the door shut on its own
- Hinges sagging so the door no longer meets the frame squarely
- Heated frames and door sweeps that have stopped heating
- Strip curtains missing, shortened or pushed aside permanently
- Anything that staff have taken to propping the door open with
These are among the cheapest repairs in refrigeration and among the most expensive to ignore.
Questions we get on the phone
My freezer is running constantly. Is that bad?
A freezer runs a lot by design, but it should still cycle. One that never stops is working against something — ice on the coil, a dirty condenser, a refrigerant leak or a door that is not sealing. It is also running up your power bill while it does.
Can I just chip the ice off myself?
Please do not. Evaporator coils and the tubing in them are soft, and a screwdriver through a coil turns an inconvenient repair into a very expensive one. Clearing ice is fine; clearing it off a coil with a tool is not.
How cold should it actually be?
Most operations run −18 to −23 °C. Colder is not automatically better — it costs more to run and makes the defrost job harder. What matters more is that it holds steady rather than swinging.
The temperature is fine but there is ice everywhere. Can it wait?
Not really. Ice is the warning that arrives before the temperature problem does. A coil that is icing faster than defrost can clear it will reach the point of blocking airflow, and then the box warms up with no further notice.
How often should a freezer be serviced?
At least twice a year, and freezers reward attention more than coolers because the defrost system has more to go wrong. See maintenance plans.
Ice coming back faster than it clears?
Call and describe where the ice is forming and what the controller reads. That usually tells us what to bring.