LG Microwave Is Tripping Circuit Breaker — Troubleshooting Guide

When your LG microwave trips the circuit breaker, it indicates either an overcurrent condition in the microwave or a circuit capacity issue. LG NeoChef Smart Inverter microwaves draw up to 15 amps during full-power operation — combined with other appliances on the same circuit, this easily exceeds a standard 20-amp breaker. However, repeated tripping on a dedicated circuit points to an internal fault that requires diagnosis.

LG Microwave Power Requirements

LG microwaves have specific electrical demands that differ from conventional units:

• NeoChef Countertop (LMC series): 1200-1800W cooking power, 12-15A draw on 120V circuit
• Over-the-Range (LMVH/LMHM series): 1000-1100W cooking + exhaust fan, 13-15A total
• Microwave Drawers (LMD series): 950-1200W, 10-13A

LG Smart Inverter technology draws current more consistently than conventional microwaves. A traditional microwave cycles the magnetron on/off (creating brief zero-draw periods), but the inverter maintains continuous draw. This means an LG Smart Inverter model drawing 14A sustains that draw throughout the entire cook cycle — no brief relief for the circuit.

Most Common Causes (Ranked by Likelihood)

1. Overloaded Shared Circuit (30% of cases)

The most frequent cause isn't a microwave fault at all — it's a circuit capacity issue. LG microwaves require a dedicated 20A circuit per their installation specifications. Many kitchens, especially in older homes, share the microwave circuit with other outlets powering toasters, coffee makers, or dishwashers.

Symptoms: Breaker trips only when microwave runs simultaneously with another appliance, trips during high-power cooking but not at lower power levels, never trips on high speed fan only.

Diagnosis:

1. Identify which breaker controls your microwave outlet
2. Determine what else is on that circuit (plug a lamp into various outlets, turn off the microwave breaker, see what goes dark)
3. LG over-the-range microwaves should be on their own dedicated 20A circuit per NEC requirements
4. If shared, the solution is either electrical work (dedicated circuit) or usage discipline (don't run simultaneous high-draw appliances)

Fix Cost: $0 (usage change) to $200–$500 (electrician runs dedicated circuit)

2. Shorted High-Voltage Capacitor (25% of cases)

The high-voltage capacitor in LG microwaves (rated approximately 2100V, 1.0-1.14 microfarads) stores energy that doubles the voltage for the magnetron. When this capacitor develops an internal short, it draws excessive current the moment the high-voltage circuit energizes, tripping the breaker instantly.

On LG Smart Inverter models, the main HV capacitor is smaller but there are additional capacitors on the inverter board that can also short.

Symptoms: Breaker trips the instant you press Start (within 1-2 seconds), trips before any heating occurs, trips consistently on any power level, trips even in a short timed-cook test.

LG-Specific Diagnosis:

1. Unplug, remove cabinet (Torx T15)
2. Discharge the HV capacitor safely (resistor across terminals — never short with a screwdriver on LG inverter models as it can damage the inverter board)
3. Test capacitor with multimeter on capacitance setting — should read within 10% of rated value
4. Check for visible damage: bulging top, leaking electrolyte, burn marks on casing
5. On Smart Inverter models, also inspect smaller capacitors on the inverter PCB for bulging

Parts Cost: $30–$70 (HV capacitor) Professional Repair Cost: $150–$280 DIY Difficulty: Advanced — lethal voltages involved

3. Shorted Magnetron (20% of cases)

A magnetron with shorted windings draws excessive current from the power supply, exceeding the circuit breaker's trip threshold. In LG Smart Inverter models, a shorted magnetron can also damage the inverter board because the inverter attempts to regulate current to a dead short — causing it to draw maximum input current before its own protection triggers.

Symptoms: Breaker trips 3-5 seconds after Start (magnetron energizes with delay), trips with burning smell, trips with visible arcing at the waveguide cover, previously worked fine but gradually started tripping more frequently.

LG-Specific Diagnosis:

1. Check waveguide cover first — severe arcing damage there can lead to magnetron shorts
2. Access magnetron (cabinet removal required): disconnect the 2 HV leads
3. Test magnetron filament: should read <1 ohm between filament terminals
4. Test for shorts: should read infinity (open) between each filament terminal and the magnetron case (ground)
5. Any reading other than infinity to ground = shorted magnetron

Parts Cost: $80–$200 (LG magnetron) Professional Repair Cost: $250–$400 DIY Difficulty: Advanced

4. Door Switch Short Circuit (15% of cases)

When the LG microwave's monitor switch fails, it's designed to create a deliberate short circuit to blow the internal fuse. However, if the internal fuse has been previously replaced with a higher-rated fuse (improper repair), or if the short occurs at a point before the fuse, it will trip the house circuit breaker instead.

Some LG models have a configuration where one door switch wire routes directly from the line input — a short in this switch trips the breaker before the internal fuse can act.

Symptoms: Breaker trips when door is closed (not when Start pressed), trips when door is slammed, intermittent — some closings fine, others trip breaker, trips occur even without attempting to cook.

LG-Specific Fix:

1. Unplug, access door switch assembly
2. Test all three switches with multimeter
3. Check if internal fuse was previously replaced with wrong rating (should be 20A ceramic for most LG)
4. Replace faulty switches — LG 6600W1K004F
5. Inspect all switch wiring for chafed insulation that could short to chassis ground

Parts Cost: $15–$35/switch + $5 (fuse if needed) Professional Repair Cost: $150–$280 DIY Difficulty: Moderate to Advanced

5. Shorted Turntable Motor (10% of cases)

The turntable motor in LG microwaves draws minimal current normally, but a shorted winding can draw enough to add 2-3 amps to the circuit load — pushing a marginal circuit over the breaker threshold. This cause is most likely when the breaker was borderline before (shared circuit) and the motor short added just enough to trip.

Symptoms: Breaker trips a few seconds after Start (after turntable begins rotating), microwave works if turntable motor is disconnected, turntable motor hot to the touch.

Parts Cost: $15–$40 Professional Repair Cost: $100–$180 DIY Difficulty: Easy to Moderate

Diagnostic Flowchart

Safety Notes for LG Microwave Electrical Work

• Always unplug — never work on a microwave connected to power
• The HV capacitor retains lethal charge (2100V+) even unplugged — must be discharged with proper resistor
• On LG Smart Inverter models, the inverter board has its own capacitors requiring separate discharge
• If your breaker is GFCI or AFCI type, the trip may indicate a ground fault rather than overcurrent — these breaker types are more sensitive and may require different diagnostic approach
• Never replace the internal fuse with a higher-rated fuse — this defeats the safety system

Prevention Tips

• Ensure your LG microwave is on a dedicated 20-amp circuit (required by LG installation specifications)
• Use a surge protector rated for microwave draw (1800W minimum) to protect inverter board components from spikes that degrade capacitors
• If breaker trips once and microwave works fine afterward, monitor — intermittent shorts often worsen gradually
• Keep ventilation clear on over-the-range models — overheating accelerates component degradation
• Replace waveguide covers proactively to prevent arcing that can damage the magnetron

FAQ

Q: Can I use a higher-amp breaker to stop my LG microwave from tripping? Absolutely not. The breaker protects your home wiring from fire. If the circuit trips at 20A, the wiring is rated for 20A. A higher breaker allows the wire to overheat, creating fire risk. Fix the microwave or circuit — never the breaker.

Q: My LG microwave trips the GFCI outlet but works on a regular outlet — why? LG microwaves can have small ground leakage currents that trip GFCI outlets without indicating a fault. However, NEC does not require GFCI protection for dedicated microwave circuits. If your microwave is on a GFCI outlet, consult an electrician about proper circuit configuration.

Q: Does tripping the breaker damage my LG microwave? Repeated breaker trips create voltage transients when power is abruptly cut. On LG Smart Inverter models, these transients can damage the inverter board over time. Resolve the tripping cause promptly.

---

Electrical faults in microwaves require proper diagnosis. Our technicians safely test high-voltage components and carry LG capacitors, magnetrons, and control boards. Schedule a diagnostic →