LG Therma V R290 Monobloc Hydro Unit: Installation Guide

• Major components are already built in. The backup heater, 3-way valve, and 12-litre expansion tank come pre-installed inside the unit, so there's far less to assemble, wire, and connect on site than a traditional component-by-component setup.

• No refrigerant work required. The Hydro Unit links to the R290 Monobloc outdoor unit with water piping only — removing on-site refrigerant handling and the specialist work that comes with it.

• A wall-hung installation designed for efficient setup. At about 33.6 kg and 700 × 420 × 299 mm, the unit hangs on a bracket rather than taking up floor space with most mounting tasks requiring minimal personnel.

• Straightforward piping, wiring, and configuration. Six clearly marked threaded ports, two dedicated cable entries, and DIP switches that ship in a standard default setting keep each stage logical and quick to work through.

• Guided commissioning through the HMI. The built-in Commissioning Wizard and Backup Heater Wiring Test walk you through start-up step by step, and built-in Wi-Fi pairs to the LG ThinQ app with no extra modem to fit.

Setting up a heat pump indoors has usually meant piecing together a number of components on site: the indoor unit, an expansion vessel, 3-way valves, a backup heater, and all the wiring that ties them together. LG's Therma V R290 Monobloc Hydro Unit does away with much of that, gathering the core hydronic parts inside one slim, wall-hung unit built to deliver space heating and cooling. 

It works with an R290 Monobloc outdoor unit and calls for nothing more than water piping between the two, meaning no refrigerant work is needed on site. This guide takes you through the install from beginning to end.

It's useful to know where the Hydro Unit falls within LG's three indoor choices. At the entry point is the Control Unit, which carries only the HMI controller and Indoor unit PCB. At the other end is the Combi Unit, which packs a 200-liter hot water tank into one floor-standing cabinet so a single appliance covers both heating and hot water. The Hydro Unit lands in the middle: a unit that already houses the backup heater, 3-way valve, and 12-liter expansion tank, set up to drive a heating circuit and work with a separate hot water tank connected alongside it.

Much of what makes the Hydro Unit appealing comes down to that wall-hung format. Weighing about 33.6 kg and measuring 700(H) × 420(W) × 299(D) mm, it fixes to a bracket rather than occupying floor space, and through most of the installation a single person can manage it.

*This article is an informal visual overview to help qualified installers follow LG’s official documentation. It is not an installation manual and must not be used as the sole basis for design, installation, or commissioning.

With the unit selected, the first thing to sort out on site is where it will hang. Before lifting it into position, check that the wall is sound and can carry the load, that a drain is within reach, and that the service clearances the unit needs can be held. At roughly 33.6 kg the Hydro Unit is light next to a floor-standing cabinet, but a firm, correctly fixed wall still matters, both for safe mounting and for reaching the unit when it later needs servicing.

2-1. Prepare location:

 • A water-resistant floor beneath the unit with access to the home's drainage.

 • Enough service space secured on every side.

 • No flammable materials in the surrounding area.

 • Nothing set in front of the unit that would get in the way of access.

2-2. Confirm minimum clearance:

 • Left and right sides: 200 mm

 • Top: 250 mm

 • Front: 500 mm

 • Bottom: 1,300 mm

With the wall ready, the unit can go up and be opened out for the connections that follow. Rather than standing on the floor, the Hydro Unit hangs from a bracket, so the work is mainly about fixing that bracket securely and hooking the unit onto it. Its light weight means one person can handle most of this, though care is needed not to knock the control panel while lifting.

3-1. Get the unit onto the wall:

 • Drill 2 of the M8 anchor bolts into the wall and fit the mounting bracket to them, checking it sits perfectly level.

 • Lift the unit into place, taking care not to damage the control panel as you raise it.

 • Hang the unit on the bracket, making sure the bracket hook seats into the hole below so the unit is properly held.

Now that the unit is hung and open, the plumbing comes next: joining up the water circuits that move heat through the system. The Hydro Unit brings its connections out through six threaded ports on the underside, so each pipe is sealed onto the thread with Teflon tape rather than pressed into place. Use the port layout marked on the unit to keep track of which connection is which as you work.

With the water side finished, the focus shifts to the electrical connections. The Hydro Unit provides two cable entries to help with that: Hole A for the DC line running to the PCB and Hole B for the AC line running to the terminal block. Switch off the power supply before starting any wiring.

*All electrical work, including wiring of the indoor unit, backup heater, and protection devices, must be carried out by a licensed electrician in accordance with national wiring standards and LG’s official installation manual.

5-1. Routing Each Cable Through the Correct Entry:

 • Hole A— the DC line, connected to the PCB inside the control box.

 • Hole B— the AC line, connected to the terminal block.

 • Fit round pressure (ring) terminals at the power terminal block and ensure the wiring is long enough for the indoor unit control box to open freely on its hinge after connection.

Now that the wiring is complete, set the required system configuration using the DIP switches on the indoor unit PCB. Match the settings to the installed options, such as domestic hot water, heating and cooling mode, backup heater capacity. Always cut the power before changing the DIP switch settings. The factory settings are suitable for a standard installation, so only change the switches needed for your setup.

6-1. The Main Settings to Check:

 • SW2-2 and SW2-3 — accessory information: set these to match your setup, whether that's the heat pump alone, the heat pump with a DHW tank, or the heat pump with a DHW tank plus a solar thermal system.

 • SW2-4 — cycle: leave OFF for heating only, or set ON to enable cooling.

 • SW2-6 and SW2-7 — backup heater capacity: set this combination to suit the heater fitted, matching the phase and step wired in Section 5.

 • SW1-3 — outdoor-to-indoor communication: ON for the RS-485 method (9600 bps), OFF for the AC method.

 • SW1-8 — antifreeze agent: ON where antifreeze is used, and note the CN_ANTI_SW bridge must be disconnected for the setting to take effect.

Now that everything is installed and configured, the last stage is commissioning: the checks and tests that confirm the system is safe to run before it's handed over. Working through them carefully catches any installation faults early, and the Hydro Unit's guided setup wizard keeps the process straightforward.

7-1. Begin with the Pre-Start Checks:

 • Confirm the charged water pressure reads between 2.0 and 2.5 bar, and never above 3.0 bar.  

 • Make sure the air separator cap inside the outdoor unit is left open.  

 • Confirm the communication and power wiring are correct and kept properly separated.

 • Make sure both shut-off valves on the water inlet and outlet are open.

 • Confirm that a device that secures the minimum flow rate, such as a bypass valve or hydronic separator, is fitted; otherwise, flow switch error (CH14) can occur.

 • Check that the unit is fixed tightly to the wall so it can't vibrate or work loose in operation

7-2. Running the Tests and Starting Up:

 • Use the Commissioning Wizard to work through the installer settings and start-up in guided steps.

 • Run the Backup Heater Wiring Test from the HMI setup menu; a result of "checked" confirms the heater is wired correctly.

 • On first power-up, run the unit for a 6-hour preheat before full operation to warm the compressor oil.