LG WZ18AWN (18,000 BTU, 5.05 kW) - Inverter Pro wall-mounted inverter air conditioner with Wi-Fi

The 18 000 BTU Inverter Pro: plenty of cooling for a simple machine

The WZ18AWN is the 18 000 BTU machine of the basic Inverter Pro series: 5.05 kW of cooling, 5.1 kW of heating and up to 50 m² on the card. The indoor unit is larger than in the smaller models of the series - 998 by 345 mm at a depth of 210 mm - yet weighs only 11 kg, 2.5 kg less than the Deluxe H18S1D (item 1802) of the same capacity. The outdoor module measures 870 by 650 by 330 mm, weighs 38 kg and is rated 54 dB(A), the same level as the 9 000 BTU machine of this series and 6 dB quieter than Deluxe. The logic of the series survives at this capacity: no mirrored panel, no screen, no ultraviolet treatment, but an inverter compressor, Wi-Fi and the simplest installation in its class. Energy classes A++ in cooling and A+ in heating are no record, but for a machine used seasonally they are entirely adequate.

5 kW over 50 m²: mounting height and airflow direction

For a 50 m² space the decisive factor is not capacity but geometry: a wall unit throws air in one direction, and whether the temperature is even depends on how it is oriented. The unit goes on the shorter wall so that the stream runs along the length of the room, at a height of 2.4-2.6 m - higher and the stream dies against the ceiling, lower and it blows onto people's heads. The throw of an 18 000 BTU unit reaches about 9-11 metres, so in a room 8 by 6 metres the far corner is served, while in a space 12 by 4 metres it probably is not. Automatically swinging louvres help mix the air but do not substitute for correct placement. If the space has partitions, an archway or a corridor, a wall unit serves only the part it can see: in those cases a CL18R cassette (item 1826) or a CT18R ducted unit (item 1836) is the answer.

5.05 kW of cooling and 5.1 kW of heating: a machine built for summer

In this series cooling and heating capacities are practically equal - 5.05 against 5.1 kW - while the Deluxe machine of the same size offers 800 W more heat. That means the unit is designed first as an air conditioner, with heating a working but secondary mode. For a 50 m² space, 5.1 kW of heat will show a real effect in the shoulder season only if the building is reasonably insulated: in an uninsulated extension it will not be enough. The operating envelope of LG residential R32 splits runs roughly from -10 to +48 °C in cooling and down to about -10 °C in heating, and the exact figures for a given variant are worth checking against the data sheet. If the brief includes heating in cold weather, the correct answer is a Therma V heat pump such as the HU141MA.U33RU (item 1882) rather than an air conditioner.

29 dB: why the larger model is louder and where that matters

The rated 29 dB(A) of the indoor unit is more than the 25 dB(A) of the 9 000 and 12 000 BTU machines in this series, and the reason is simple: to move the air for 5 kW of cooling the fan has to turn faster. In a space with people, equipment and street noise, 29 dB(A) goes unnoticed, but in a quiet office at night the machine is present in the soundscape. For an office that is fine; for a 50 m² bedroom it deserves thought, because two smaller units, each running quietly, are often the better arrangement. The outdoor module is rated 54 dB(A), which is modest for this capacity, and that is one reason to choose this series in dense housing. Vibration mounts, a flexible section in the pipework and brackets with stiffness to spare remove most of the structure-borne noise that would otherwise travel through the wall.

Runs up to 25 metres and a 1/2 inch line

From this capacity the installation changes: a 1/4 inch liquid line, a 1/2 inch (12.7 mm) gas line, a maximum run of 25 m and 15 m of height difference. A 1/2 inch tube bends only with a bender, and at turns inside walls it is often simpler to fit ready-made elbows than to form a radius in place. Beyond 7-8 metres of run the R32 charge needs topping up at the specified rate per metre, and that is something to raise with the installers before the work starts rather than after. On vertical sections longer than 5-6 metres the gas line gets oil traps - without them oil slowly collects at the bottom and the compressor runs without proper lubrication. Insulation goes on each pipe separately, and outdoors it is covered by a duct: in two or three seasons exposed insulation is destroyed by ultraviolet and stops doing its job.

Electrics and consumption

The machine is single-phase, 220-240 V, 50 Hz; at full cooling it draws roughly 1.6-1.8 kW, that is 7-8 A. The circuit is run separately: 2.5 mm² copper over a short distance, or 4 mm² if the board is more than 20 metres from the unit, with its own breaker. Class A++ means that through a typical season the machine spends most of its time at 30-50 per cent of capacity, so average consumption lands closer to 600-900 W than to the peak. An inverter start produces no current surge, which makes the unit compatible with a generator or UPS of sensible size - significant for a commercial space with supply interruptions. Where mains voltage is unstable a protection relay is fitted: it costs incomparably less than an inverter board.

Which jobs it fits and where it is out of place

The WZ18AWN suits a large living room, a studio, a small shop, an office for 8-10 people or a workshop of 35-50 m² where the machine works mainly in the warm season. It wins especially where installation is awkward: an 11 kg indoor unit and a 54 dB(A) outdoor module let the equipment go where something heavier and louder would create problems with the neighbours or the facade. Where the model is out of place: spaces with partitions and separate offices; halls with ceilings above 3.5 m; sites where the machine runs many hours daily and the more efficient A+++ class pays for itself. A server room or any space that has to be cooled in frost needs a unit with a low-ambient kit rather than a residential series. And if this capacity is wanted specifically for winter heating, that is a job for a heat pump, not an air conditioner.

How it differs from neighbouring models in this catalogue

The WZ12AWN (item 1805) is the 12 000 BTU machine of this series: 3.45 kW of cooling for 35 m², a lighter 9.2 kg indoor unit, a 3/8 inch line and a 15 m run - a substantially simpler installation. The WZ24AWN (item 1807) is the 24 000 BTU Inverter Pro at 6.95 kW for 70 m², with a 5/8 inch line, a 30 m run and a 46 kg outdoor unit. The H18S1D (item 1802) is the Deluxe machine of this size rated A+++ at 23 dB(A): dearer, quieter indoors, more frugal in daily duty, but with a louder 60 dB(A) outdoor unit. The PC18SQ (item 1808) is the Standard Plus 5 kW machine with Wi-Fi: a different line with the same output and the same A++ class. The CT18R (item 1836) is a cassette of the same output for a space with a suspended ceiling: a dearer installation, but even four-way air distribution.

Send us the room dimensions and the spot for the outdoor unit, and we will work out whether one 18 000 BTU machine is enough and where to hang it so that no cold zone forms beneath it.