LG Therma V HM091MRS User Manual (English)

Questions and Answers:

C
Carol SweeneyAug 7, 2025
Why is my LG Heat Pump heating or cooling not satisfactory?
- B
  Brian DanielsAug 7, 2025
  If your LG Heat Pump isn't heating or cooling properly, make sure the target temperature is set correctly, distinguishing between water-based and air-based settings. Insufficient charged water could be the cause; check the pressure gauge and add water until it reads 2~2.5 Bar. Also, a low water flow rate might be the issue. Inspect the strainer for particle buildup and clean if necessary. Ensure the pressure gauge isn't above 4 Bar, and check the water pipe for obstructions from particles or lime.
T
Tamara HarperAug 13, 2025
What to do if my LG Heat Pump doesn't start, although electric power supply is OK?
- S
  Stephanie ShortAug 13, 2025
  If your LG Heat Pump isn't starting even with power, it might be due to the water inlet temperature. The unit won't start if the water inlet temperature is above 57 °C to protect the system. Also, the unit won't operate if the water inlet temperature is below 5 °C during cooling or below 15 °C during heating. Wait for the unit to warm up the water. If you're not using a back-up heater accessory, increase the water temperature with an external heat source.
R
Rachel SimonAug 22, 2025
How to fix water pump noise in my LG Therma V HM091MRS Heat Pump?
- E
  Edward OnealAug 22, 2025
  To address water pump noise in your LG Heat Pump: First, ensure air purging is completely finished by opening the air purge cap and adding water until the pressure gauge reads 2~2.5 Bar. Check if water splashes out like a fountain when the tip is pressed; if not, continue purging. Also, check if the pressure gauge indicates above 0.3 Bar and verify the expansion tank and pressure gauge are operating correctly, as low water pressure could be the cause.
V
Valerie HillAug 28, 2025
What to do if water is flood out through drain hose in my LG Therma V HM091MRS Heat Pump?
- J
  Jennifer BlackAug 28, 2025
  If water is flooding out through the drain hose of your LG Heat Pump, it might be due to too much water being charged. Open the safety valve switch until the pressure gauge indicates 2~2.5 Bar to release excess water. Another possible cause is a damaged expansion tank, which would need to be replaced. Also, check if the thermal protector of the water tank heater is activated.

LG Therma V HM091MRS Specifications

General

Type	Air to Water Heat Pump
Model	HM091MRS
Heating Capacity	9.0 kW
Energy Efficiency Class Heating	A++
Refrigerant	R32
Cooling Capacity	8 kW
Power Supply	220-240 V, 50 Hz

Summary

Preface

Safety Instructions

Installation Part

General Information

Model Information

Details on product model naming conventions and specifications.

Model name and related information

Table listing model names, capacities, and power sources.

Parts and Dimensions

Identifies and illustrates the main parts and dimensions of the unit.

Control Parts

Diagrams and descriptions of the unit's control box components.

Remote Controller

Explanation of the remote controller's display and buttons.

Typical Installation Example

Illustrates conceptual installation scenarios for heating and cooling.

Cycle Diagram

Visual representation of the refrigerant and water cycles within the unit.

Water cycle

Schematic diagram showing the water flow for basic and advanced installations.

Installation

Transporting the Unit

Guidelines for safely lifting and moving the unit during installation.

Installation places

Recommendations for selecting an optimal and safe location for the unit.

Installation at Seaside

Specific considerations for installing the unit near coastal areas.

Seasonal Wind and Cautions in Winter

Precautions for operating the unit in areas with heavy snow or cold weather.

Foundation for Installation

Instructions for preparing a stable and level foundation for the unit.

Electrical Wiring

Requirements and warnings for connecting the unit's electrical supply.

Wiring of main power supply and equipment capacity

Guidance on selecting appropriate power supply and cable specifications.

Water Piping and Water Circuit Connection

Steps and considerations for connecting the unit's water pipes.

Water Charging

Procedures for filling the system with water and purging air.

Pipe Insulation

Importance and purpose of insulating water pipes for efficiency and protection.

Water pump Capacity

Information on setting the water pump's variable capacity for optimal performance.

Pressure Drop

Considerations for pressure loss in the system and pump selection.

Performance curve

Charts showing pump performance based on flow rate and head.

Water Quality

Requirements for water quality in the heating system.

Frost protection

Instructions for using antifreeze solutions to prevent freezing.

Water Volume and Expansion Vessel Pressure

Guidance on adjusting expansion vessel pre-pressure based on water volume.

Accessories Installation

Accessories supported by LG Electronics

List of compatible accessories and their models from LG.

Accessories supported by 3rd party Companies

List of compatible accessories and their specifications from third parties.

Before Installation

General precautions and warnings before installing any accessory.

Thermostat

Information on thermostat types, installation conditions, and placement.

2nd Circuit

Guidance on setting up a second heating/cooling circuit with a Mix Kit.

3rd Party Boiler

Instructions for connecting and controlling an auxiliary boiler.

3rd Party Controller

How to connect external controllers using Modbus protocol.

Meter Interface

Installation of a module to monitor energy and power generation.

Central Controller

Methods for installing the PI485 PCB for central control.

Remote Controller

Instructions for mounting and wiring the wired remote controller.

DHW Tank

Considerations for installing a Domestic Hot Water tank and its components.

Solar Thermal Kit

Procedures for connecting the solar thermal kit for hot water heating.

Dry Contact

Installation of a switch for HVAC system automatic control.

External Controller - Setting up programmable digital input operation

Connecting an external controller for ON/OFF control via digital input.

Remote Temperature Sensor

Guidelines for installing a remote sensor to detect ambient temperature.

Solar pump

How to install a solar pump to energize water flow in the solar thermal system.

External pump

Installing an external pump for large rooms or insufficient insulation.

Wi-fi Modem

Installing a modem for remote system operation via smartphone.

Energy State

Information on available energy states for optimizing renewable energy usage.

Digital Input for energy saving (ESS, Smart Grid)

Setting up digital inputs for energy saving modes and smart grid integration.

2Way Valve

Wiring and installation of a 2-way valve for water flow control.

3Way Valve(A)

Installation and wiring of a 3-way valve for DHW tank or floor heating.

3Way Valve(B)

Installation and wiring of a 3-way valve for solar thermal system control.

Electric Heater

Instructions for piping and wiring the electric heater accessory.

Final check

A checklist of critical items before completing accessory installation.

Configuration

DIP Switch Setting

Instructions for setting DIP switches on the indoor PCB for system configuration.

DIP Switch Information

Details on the function and settings of Option Switch 2.

Option Switch 1

Configuration options for MODBUS and MODBUS Function.

Option Switch 3

Settings for Remote Air Sensor and Antifreeze solution usage.

Outdoor PCB General Information

Overview of the outdoor PCB and its DIP switch SW2.

Emergency Operation

Explanation of system troubles, classified troubles, and emergency modes.

Service Setting

How to enter service setting

Steps to access the service menu on the remote controller.

Service setting

Overview of available product service functions.

Service Contact

How to check and input service center contact information.

Model Information

How to view product and capacity information via the remote controller.

RMC Version Information

How to check the software version of the remote controller.

Open Source License

Accessing information about the open source software used.

Installer Setting

How to enter installer setting

Procedure to access the installer settings menu using a password.

Installer setting

A comprehensive list of installer-configurable functions and parameters.

3 Minutes Delay

Temporarily bypasses the 3-minute delay for outdoor unit components.

Select Temperature Sensor

Configuration for using air or water temperature sensors for control.

Dry Contact Mode

Setting the dry contact function for external control signals.

Air cooling set temp

Setting the temperature range for cooling based on air temperature.

Water heating set temp

Setting the temperature range for heating based on water temperature.

DHW set temp

Setting the target temperature for Domestic Hot Water.

Screed drying

Controls floor heating temperature for curing concrete structures.

Tank disinfection setting 1, 2

Configuring special modes for DHW tank disinfection against legionella.

Heater priority

Determining the priority between electric heater and DHW tank heater.

DHW time setting

Setting operation times, stop times, and delay times for DHW heating.

Seasonal auto temp

Setting operational reference values for Seasonal Auto mode.

Anti-freezing Temperature

Setting the temperature to prevent frostbite and system freezing.

Solar Thermal System

Setting operation reference values for the solar thermal system.

Energy state

Controlling product operation based on Energy Storage System (ESS) states.

Password Initialization

Resetting the remote controller password to its default value.

Commissioning

Check List before Starting Operation

Pre-operation checklist covering wiring, pressure, and installation checks.

Starting Operation

Steps and checks to perform before initiating the unit's first operation.

Check before Starting Operation

Verifying refrigerant leakage, power connection, and insulation resistance.

Starting Operation flow chart

A flowchart guiding the initial operational test sequence.

Airborne Noise Emission

Information on the unit's noise emission levels and exposure factors.

Vacuum & Charge of Refrigerant

Procedures for vacuuming the system and charging refrigerant.

1. Vacuum

Steps for performing the vacuum action on the refrigerant circuit.

2. Charge of refrigerant

Process for charging the correct amount of refrigerant into the system.

3. Location of SVC port

Identifying the Service Valve (SVC) ports on the unit.

How to drain remaining water in the product

Instructions for draining water from the unit to prevent freezing during storage.

Troubleshooting

Guidance for diagnosing and resolving operational issues and errors.

Troubleshooting for Problem while Operation

Common problems during operation and their solutions.

Troubleshooting for Error Code

A list of error codes, their causes, and corresponding check points.

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LG Therma V HM091MRS User Manual

Table of Contents

Questions and Answers:

LG Therma V HM091MRS Specifications

Summary

Preface

Safety Instructions

Installation Part

General Information

Model Information

Model name and related information

Parts and Dimensions

Control Parts

Remote Controller

Typical Installation Example

Cycle Diagram

Water cycle

Installation

Transporting the Unit

Installation places

Installation at Seaside

Seasonal Wind and Cautions in Winter

Foundation for Installation

Electrical Wiring

Wiring of main power supply and equipment capacity

Water Piping and Water Circuit Connection

Water Charging

Pipe Insulation

Water pump Capacity

Pressure Drop

Performance curve

Water Quality

Frost protection

Water Volume and Expansion Vessel Pressure

Accessories Installation

Accessories supported by LG Electronics

Accessories supported by 3rd party Companies

Before Installation

Thermostat

2nd Circuit

3rd Party Boiler

3rd Party Controller

Meter Interface

Central Controller

Remote Controller

DHW Tank

Solar Thermal Kit

Dry Contact

External Controller - Setting up programmable digital input operation

Remote Temperature Sensor

Solar pump

External pump

Wi-fi Modem

Energy State

Digital Input for energy saving (ESS, Smart Grid)

2Way Valve

3Way Valve(A)

3Way Valve(B)

Electric Heater

Final check

Configuration

DIP Switch Setting

DIP Switch Information

Option Switch 1

Option Switch 3

Outdoor PCB General Information

Emergency Operation

Service Setting

How to enter service setting

Service setting

Service Contact

Model Information

RMC Version Information

Open Source License

Installer Setting

How to enter installer setting

Installer setting

3 Minutes Delay

Select Temperature Sensor

Dry Contact Mode