LG heat pump water heater

LG Inverter heat pump (2020 manual) error codes

Covers: LG Inverter Heat Pump Water Heater - Owner's Manual MFL71409201 Rev.01 (04/24/20) code set

Every code listed in LG's own manual for this series, with what it means and what LG says to do. Last checked 2026-10-03.

Is this your model? From LG's 2020 owner's manual (MFL71409201). The manual prints no model numbers, and LG's current product listings link the newer manual instead. If your code isn't here, check the 2024–2025 manual.

LG's manual for this series does not list error codes; see the troubleshooting section below.

Troubleshooting without a code

• Insufficient or no hot water

  Likely cause: Water usage exceeds the capacity of the water heater in current mode

  What to do: Wait for the water heater to recover after an abnormal demand. Change the mode for higher recovery.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Water temperature set too low

  What to do: See the "Water Temperature Adjustment" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: ECO tripped

  What to do: See "Safety Controls" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: No electric supply to the water heater

  What to do: Check the electric supply to the water heater. See "Making Electrical Connections" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Water connections to unit are reversed

  What to do: Re-install water connection correctly

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Leak in hot water faucets or plumbing system

  What to do: Make certain all faucets are closed. Check home for any leaks and repair

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Improper electric wiring

  What to do: See "Making Electrical Connections" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Cold water inlet temperature may be lower in winter

  What to do: This is normal. The colder inlet water takes longer to heat.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Dirty air filter

  What to do: See "Air Filter Maintenance" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Not enough clearance to air exchange for heat pump

  What to do: Make sure unit has enough clearance. See "Select the best Location" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 30

• Insufficient or no hot water

  Likely cause: Open fuse or a circuit breaker tripped

  What to do: Replace fuse or reset circuit breaker.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Water is too hot

  Likely cause: Water temperature set too high

  What to do: See the "Water Temperature Adjustment" section.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Noise

  Likely cause: The heat pump compressor, fan, or EEV valve is running

  What to do: This is normal

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Noise

  Likely cause: Build up of scale or lime deposits on heating elements may cause rumbling noise

  What to do: Clean or replace the heating elements. This should only be performed by qualified service person. Call our Technical Support Center.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Drips from the outside of the heater

  Likely cause: Condensate drain is blocked

  What to do: Clean the drain port and remove the debris.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Drips from the outside of the heater

  Likely cause: Hot/Cold water connections or other parts have loosened

  What to do: Tighten the loose connections. This should only be done by a qualified service person.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Noise and drips from relief valve

  Likely cause: Pressure build-up due to thermal expansion in a closed water system.

  What to do: This is an unacceptable condition and must be corrected. Do not plug the T&P relief valve outlet. Contact a plumbing contractor to correct this.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Water odor

  Likely cause: Certain water supplies with high sulfate content will react with the anode rod

  What to do: Replacing the anode rod with less-active material rod (ex) zinc anode rod) may help reduce or eliminate the odor.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Water pressure is low

  Likely cause: Supply valve is partially closed

  What to do: Open the water heater's supply valve fully.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 31

• Trouble connecting appliance and smartphone to Wi-Fi network.

  Likely cause: The password for the Wi-Fi network was entered incorrectly.

  What to do: Delete your home Wi-Fi network and begin the registration process again.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 32

• Trouble connecting appliance and smartphone to Wi-Fi network.

  Likely cause: Mobile data for your smartphone is turned on.

  What to do: Turn off the Mobile data on your smartphone before registering the appliance.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 32

• Trouble connecting appliance and smartphone to Wi-Fi network.

  Likely cause: The wireless network name (SSID) is set incorrectly.

  What to do: The wireless network name (SSID) should be a combination of English letters and numbers. (Do not use special characters.)

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 32

• Trouble connecting appliance and smartphone to Wi-Fi network.

  Likely cause: The router frequency is not 2.4 GHz.

  What to do: Only a 2.4 GHz router frequency is supported. Set the wireless router to 2.4 GHz and connect the appliance to the wireless router.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 32

• Trouble connecting appliance and smartphone to Wi-Fi network.

  Likely cause: The distance between the appliance and the router is too far.

  What to do: If the router is too far from the appliance, the signal may be weak; move the router closer to the appliance or install a Wi-Fi repeater.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 32

Owner maintenance

• drain and flush tank

  Turn off the power by opening the circuit breaker or removing the fuses. Connect a garden hose to the drain valve and place the end of the hose in a suitable drain. Turn off the cold water supply valve. Open the drain valve (open a hot water faucet or lift the handle on the T&P relief valve to help the water drain faster). Once the tank is empty, flush the tank by opening the cold water supply valve. Allow the water to run until no more sediment drains from the tank and water runs clear. Close the drain valve and open the hot water faucet. Fill the tank by opening the cold water valve.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 26

• inspect / replace anode rod

  How often: after the first six months of operation, then annually or more frequently thereafter

  Turn off the power. Partially drain a few quarts of water through the drain valve. Pull the front decor first, then remove the top cover; lift the front panel out. Using a box wrench, unscrew the anode rod and lift it out to inspect. Replace anode rod when more than 6" of core wire is exposed at either end of the rod. To install, seal the threads with approved sealant, thread into the port and tighten using a box wrench. Fill the tank by opening the cold water valve. Artificially softened water will make the anode rod deplete faster than normal. Do not remove anode rod from the tank except for inspection.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 27

• T&P relief valve

  How often: at least annually

  Lift and release the lever handle on the water heater to ensure the waterways are clear and the valve operates freely.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 28

• clean air filter

  How often: when the "Air filter check" alarm appears on the display

  Turn off the power. Hold the knobs of the air filter, pull it and remove it from the top cover. Clean the filter with a vacuum cleaner or with lukewarm water with neutral detergent. Dry the filter in the shade. Insert the air filter into the top cover and check the top cover for correct assembly of the air filter. (The air filter can be broken when it is bent.)

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 28

• reset air filter alarm

  The device will display an alarm icon reminding you to check and clean the air filter periodically. Press and hold Set button about 3 seconds to reset the alarm.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 22

• condensate drain

  Remove the condensate drain lines and connections. Pull the front decor first, then remove the top cover; lift the front panel out, then slightly lift the rear panel and remove it. Check the condensate drain pan for any debris, and clean the condensate drain by wiping out with a damp cloth or pouring a cup of bleach. Reattach top cover and side panel and connect the condensate drain line. Restore power to the water heater.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 29

• extended shutdown

  Turn off the power and water supply and drain the water heater to conserve energy and prevent a buildup of dangerous hydrogen gas. Drain heater and piping if they might be subjected to freezing temperatures. After a long shutdown, operation and controls should be checked by qualified service personnel; make certain the heater is completely filled again before placing it in operation.

  Source: LG Heat Pump Water Heater Owner's Manual, MFL71409201 Rev.01, page 29

Sources

• LG Heat Pump Water Heater Owner's Manual (MFL71409201 Rev.01)