How to defrost a chest deep freezer safely and quickly

When to defrost

• When ice on the walls reaches roughly 5 mm thick, or sooner if it is affecting the lid seal.
• When the lid does not close flat because of ice on the rim.
• When the freezer is struggling to hold −18 °C or colder, or running almost continuously, and the ice is heavy.
• Before a seasonal peak — clear the ice in the slow weeks, not the week before Diwali or summer stocking.
• In humid coastal cities, expect to defrost more often than in dry inland ones; in the monsoon, more often still.

Plan where the stock will go

The defrost itself takes a few hours, plus several more for the empty freezer to pull back down to temperature before you reload. Pick the quietest day and time, and empty it when stock is lowest.

Move stock into another freezer if you have one. If not, pack it tightly in insulated boxes or cool boxes with frozen gel packs, keep the boxes closed and in the coolest place available, and group items so that the most sensitive products — ice cream, frozen desserts — go into the best-insulated box and go back first. Do not leave cartons open on the counter.

Step by step

• 1. Switch off and unplug the freezer. Do not just turn the thermostat to its warmest setting.
• 2. Empty it completely and remove baskets and dividers.
• 3. Find the drain plug, usually inside at the bottom and on the outside at the front or side. Open both and place a shallow tray or the supplied drain cap under the outlet. If there is no drain, lay old towels in the bottom.
• 4. Leave the lid open. In a warm room, ice starts loosening within 30–60 minutes.
• 5. To speed things up, place bowls or pans of hot (not boiling) water on a folded towel in the bottom and close the lid for 10–15 minutes. Replace the water as it cools.
• 6. As sheets of ice loosen, lift them out by hand or ease them away with a plastic or wooden scraper. Never lever against the wall.
• 7. Mop up meltwater as you go so it does not overflow the drain tray onto the floor.
• 8. Once all ice is gone, wash the interior with warm water and a little mild detergent or baking soda, rinse and dry completely, including the gasket and drain channel.
• 9. Close the drain plug, close the lid and switch on. Wait until the freezer reaches its operating temperature — this can take several hours — before reloading the stock, coldest items first.

What never to do

In a chest freezer, the evaporator tubing is usually bonded to the back of the thin inner liner. A knife, screwdriver or ice pick that goes through the liner punctures the tube, the refrigerant escapes and the freezer is finished unless it is professionally repaired. Many chest freezers use hydrocarbon refrigerants such as R600a or R290, which are flammable — a punctured tube in a closed shop is a fire risk as well as an expensive repair.

Do not use a hair dryer, heat gun, gas burner or room heater pointed into the cabinet. Concentrated heat warps the plastic liner and seals, and electrical appliances near standing water are a shock hazard. Do not pour boiling water directly onto the walls; sudden heat can crack liners.

How to slow ice build-up

• Keep lid openings short and few. Decide what you need before you open it.
• Check the lid seal regularly; a leaking edge builds ice fast along that side.
• Never put warm food in. Cool cooked food first in a refrigerator or blast chiller.
• Keep the freezer out of direct sun and away from steam and cooking areas.
• Do not overfill above the load line marked inside; product above it blocks the lid and sits in warmer air.

Glass-top and ultra-low freezers

Glass-top display freezers defrost the same way, but take care with the sliding lids: lift them out and stand them somewhere safe before you start, and do not put hot bowls under the glass. Ultra-low temperature freezers running at −40 °C or below often have specific defrost procedures and may hold stock that cannot be moved easily; follow the manufacturer's instructions and your own stock-protection plan.

Safety notes

Isolate power before you start, and keep extension leads and sockets away from meltwater. Wipe up water on the floor around the freezer immediately — it is a slip hazard. If you damage the liner, hear a hissing sound or smell gas, ventilate the area, keep sparks and flames away, do not switch the freezer back on, and call a technician trained to work on flammable refrigerants.