Power Outage and Your Walk-In Cooler: Before, During, After

A power outage stops your walk-in's refrigeration completely, so the box starts warming the moment the lights go out. What you do in the first minutes, and how you restart the system afterward, decides how much product you keep and whether the equipment comes back cleanly.

During the outage

1. Write down the time the power went out. Under the Conference for Food Protection emergency plan, the clock for food decisions starts then.
2. Keep the walk-in door shut. Opening refrigeration doors makes food warm faster. Put a sign on the door and tell staff not to open it.
3. Get temperature readings without opening the door much. A battery-powered thermometer or wireless sensor inside the box is ideal. Otherwise, make one planned trip to probe several TCS items in the warmest part of the box and log the readings with times.
4. Decide where product goes. If the outage looks long, choose early whether to move product from display cases into the walk-in, to a refrigerated trailer or to another location. Do it in one quick trip.
5. Keep people safe. If emergency lighting is weak, don't send anyone into a dark box alone. Wet or icy floors in and around a walk-in are slip hazards.
6. Watch for dry ice hazards if you use it (see below).

Food safety: Once product goes above 41°F, the time you have depends on the highest temperature it reached and on having a written plan and records. The limits are in the food safety guide.

How long will a walk-in hold temperature?

There is no reliable single number, and you should be wary of anyone who gives one. The USDA figures of 4 hours for a refrigerator and about 48 hours for a full freezer are for home appliances, use a 40°F threshold, and don't apply to retail. How long your walk-in holds depends on:

The only number that matters is the one on your thermometer. Keep logging.

Dry ice: useful, but treat it as a hazard

Dry ice can buy time, especially in a freezer, but it is frozen carbon dioxide and turns into carbon dioxide gas as it warms. A walk-in is a small, tightly sealed room, and gas that builds up in it can displace the air people need to breathe.

• Don't let staff work inside a box that has dry ice in it for longer than it takes to move product. Leave the door open for a few minutes before anyone goes in to work.
• Handle it with insulated gloves. Bare-skin contact causes frostbite-type burns.
• Don't put it in sealed containers.
• Keep it off direct contact with product and packaging you want to stay unfrozen, especially in a cooler.
• If anyone inside a box feels dizzy, short of breath or confused, get them out into fresh air and call 911.

When power comes back: restart in order

1. Wait for stable power. If the utility is flickering on and off, repeated restarts are hard on a compressor. Ask your technician in advance whether your plan should include switching the system off at its breaker during a long outage and back on once power is steady.
2. Check the controller display. Heatcraft's Beacon II and Smart Controller log a power-failure alarm. Heatcraft's intelliGen controller has error codes for low and high supply power (ER14 and ER15). Photograph any code before clearing it. See controller alarm codes.
3. Allow for a delay. Controllers may hold the compressor in a delay before starting. The Beacon II, for example, has a delay mode (dLY) on its display.
4. Confirm both ends are running. Evaporator fans inside should turn, and the condensing unit should start. If the condensing unit stays silent after the delay, see compressor not running.
5. Watch the breakers. A breaker that trips on restart is a technician call, not something to keep resetting. See walk-in cooler tripping breaker.
6. Watch the temperature fall. Log readings until the box is back at 41°F or below and holding. Note the time power and cooling were restored.
7. Make the food decisions. Use your temperature log and the chart in the food safety guide.

On a Heatcraft Beacon II, a system that fails to start four times in a row raises a start-up failure alarm (A3). That needs a technician.

Voltage problems after an outage

Outages often come with brownouts, surges or the loss of one leg of three-phase power. Heatcraft's condensing unit warranty conditions require:

Heatcraft also notes that its Beacon II and intelliGen boards may shut down if control voltage drops below 18 VAC. Measuring voltage means working inside live electrical enclosures, so it is a job for a technician or electrician. What staff can do is report it: lights dimming, the compressor humming without starting, or the system starting and stopping repeatedly.

Safety: Do not open electrical panels, disconnect enclosures or the condensing unit's control box to look for the problem. Check breaker and switch positions only.

Generators: sizing basics

A generator can carry a walk-in through a long outage if it is planned properly:

1. Size it from the nameplates. An electrician should size the generator from the condensing unit, evaporator and heater nameplate data. The compressor's starting current is far higher than its running current, and the generator must handle that surge.
2. Use a transfer switch. Connect through a properly installed transfer switch so the generator can never feed power back into the utility lines.
3. Match voltage and phase. A three-phase condensing unit needs three-phase power within the tolerances above.
4. Test it. Run the walk-in on the generator during a planned test, not for the first time during a storm.

Electrical service requirements for walk-ins are covered on the electrical requirements page.

Surge protection

Modern walk-in controllers are electronic boards, and power returning after an outage can arrive with spikes. Ask an electrician whether surge protective devices at the panel or at the equipment make sense for your site. It is a small cost compared with a controller board and a lost box of product.

Build an outage plan now

The most valuable outage work happens before the power goes out:

• Write a plan. The Conference for Food Protection's time and temperature chart is only available to establishments with a written plan prepared in advance.
• Install monitoring that records temperatures and alerts someone even when the store is closed. See walk-in temperature monitoring.
• Know your equipment. Record where the breakers and disconnects are, and keep your technician's after-hours number posted. The what to tell the technician checklist is worth filling in ahead of time.
• Arrange backup storage such as a refrigerated trailer supplier or a partner location.

If the walk-in doesn't recover properly after the power returns, work through walk-in cooler stopped working.