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What to Do When Your Freezer Trips the Circuit Breaker… and You Don’t Know Why

Restaurant freezer

When a freezer trips the circuit breaker intermittently, often there’s no obvious solution. Fixing the problem is a matter of perseverance.

Start by determining the type of circuit interrupter that’s tripping. That will give you a clue as to what is – and isn’t – causing the fault. Arc fault circuit interrupters (AFCIs) trip in response to power overloads and shorts. Ground fault circuit interrupters (GFCIs) trip when electricity leaves the circuit.

Here’s advice from some of our fellow techtown members who have solved that problem:

  • Plug the freezer into a different circuit. It’s possible the circuit breaker itself is faulty, or that the circuit is overloaded. If the breaker still trips, check the connections of the electrical wires to the breaker.
  • Check the freezer’s current draw at startup and during operation. Determine whether the startup, running, and defrost amperage is within the manufacturer’s specifications.
  • Inspect each wire and part. A chafed wire in the compressor or an improperly grounded wire in a frame heater could cause a short. Check for corroded connections, and sniff for a burning smell from melted wiring insulation (especially near heating elements) to narrow the problem area. Check the wires around the free-floating compressors. Because they’re stiff, they are vulnerable to torque and vibrations that may cause shorts. Also, the heaters in perimeter doors have high resistance and, if they ground somewhere during their run, may trip a GFCI.
  • Examine the heating elements. Pay particular attention to the drain heater, drain pan heater, or heated condensate pan. Remove them – even if they pass your ohm test – for a thorough visual inspection. As another issue, ice sometimes moves wires in the evaporator, and contraction and expansion during the freeze’s freeze-thaw cycle can create pinholes that lead to intermittent shorts. A pinprick hole in the defrost thermostat can be culpable, too, as moisture gradually builds up.
  • Search for heat. The heat from a faulty wire connection to a breaker or fuse block can interrupt the circuit. Let the compressor run 15 to 20 minutes, then see if the fuse is physically hot. You can do this with a laser thermometer or (better yet) a thermal imaging camera. Alternatively, run voltage tests at strategic points leading to the breaker, fuse block, or fuse to see whether the voltage drops significantly (about 1 volt of AC power). Test it with a voltmeter while the circuit is loaded, and also conduct a wire-in to wire-out test, and a terminal-in to terminal-out test. If there is a significant voltage drop, the connection or breaker is bad. Also, check the heat on nearby breakers, because excess heat may cause another breaker to trip.
  • Consider the building’s wiring. This is harder to find, but behind-the-wall wiring that is abraded or pierced by staples or nails can cause the breaker to trip.
  • Look beyond electrical. Some compressors have top-mounted compressor heads with an internal oil pump on the bottom. Pumping issues can increase amp loads that interrupt electrical circuit breakers. Be sure to check the refrigerant pressure, too, as high head pressure can overload a circuit. Also, ensure the evaporative coil and coil fan are clean.
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Intermittent shorts can take a long time to find, especially if they happen when you are not around, so be persistent. Good luck!