LG PC18SQ (18,000 BTU, 5 kW) - Standard Plus wall-mounted inverter air conditioner with Dual Inverter and Wi-Fi

Standard Plus at 18 000 BTU: a heating bias

The PC18SQ is a wall-mounted split of the Standard Plus series: 5.0 kW of cooling, 5.8 kW of heating, 18 000 BTU and up to 50 m² on the card. The second figure is the important one here: heating capacity exceeds cooling by 800 W, whereas in the basic Inverter Pro series the two are practically equal. The machine is built on a Dual Inverter compressor, runs on R32 refrigerant and is rated A++ in cooling and A+ in heating. The indoor unit measures 998 by 345 mm at a depth of 210 mm and weighs 12.7 kg; the outdoor unit is 870 by 650 by 330 mm and 38 kg. Control is twofold: an infrared remote in the box plus Wi-Fi through the LG ThinQ app, which is what separates this model from the S18EQ (item 1810) with its identical mechanics.

Dual Inverter: what lies behind the compressor name

In LG's terminology Dual Inverter means a rotary compressor with two compression chambers set 180 degrees apart. The practical point is balance: two opposed rotors cancel each other's vibration, so the compressor runs more smoothly at high speed. The second advantage is a wider frequency range: the machine can ramp up quickly at start-up and then hold temperature at low speed for a long time without switching on and off. To the user that looks like fast cooling of an overheated room followed by steady operation with no noticeable swings. The limits of the technology are worth understanding: it improves comfort and durability, but it does not compensate for a badly sized unit or a poorly sealed room.

5.8 kW of heat: what it gives you in the shoulder season

5.8 kW of heating over 50 m² is roughly 116 W per square metre, which in a reasonably insulated space with 2.7 m ceilings is enough for full heating through September-October and March-April. In practice it means the machine can not only hold a temperature but raise it from 12 to 22 degrees in an hour or an hour and a half in a 40-50 m² room. In heating mode an air conditioner moves heat in from outdoors, so it uses roughly four times less electricity than a resistive heater of the same output - the main economic argument for shoulder-season use. The envelope of LG residential R32 splits runs down to about -10 °C in heating, and the exact figure for this variant is worth checking against the data sheet before planning it as the primary heat source. In frost the machine enters outdoor-coil defrost cycles, during which heating pauses for a few minutes.

52 dB: the quietest outdoor unit among the 18 000 BTU machines here

The outdoor unit is rated 52 dB(A) - below the 54 dB(A) of the WZ18AWN (item 1806) and far below the 60 dB(A) of the Deluxe H18S1D (item 1802). For mounting on the facade of an apartment building or in an enclosed courtyard that is this model's strongest argument. The indoor unit, meanwhile, is rated 31 dB(A), more than the smaller series, because 5 kW needs a more vigorous airflow. The result is a characteristic balance: quiet outside, more noticeable in the room, which suits a shop or an office and suits a bedroom less well. Vibration mounts under the outdoor unit and a flexible section in the pipework are mandatory regardless of the decibels: 38 kg on brackets transmits vibration into the wall more strongly than the airborne noise is heard.

Installation: a 998 mm body and runs up to 25 metres

An indoor unit almost a metre long and weighing 12.7 kg needs solid through-fixings into a load-bearing wall or a structural partition: plasterboard without an embedded frame is not suitable here. Leave 10-15 cm above the unit to the ceiling and 10 cm at each side, otherwise air intake suffers and removing the filters becomes awkward. The pipework is standard for this capacity: a 1/4 inch liquid line, a 1/2 inch gas line, a maximum length of 25 m and 15 m of height difference. Runs beyond 7-8 metres require an R32 top-up at the rate per metre, and vertical sections over 5-6 metres require oil traps in the gas line. The condensate drain is laid with a constant fall of at least 1 cm per metre; where there is no fall, a condensate pump such as the ABDPG (item 1914) is fitted.

ThinQ and electrics

Wi-Fi is built in, with control through LG ThinQ: scheduling, remote switch-on, mode control and consumption statistics. A 2.4 GHz network is required - the first thing to check in a commercial space, where equipment often runs on 5 GHz only. The machine is single-phase, 220-240 V, 50 Hz; at full heating it draws roughly 1.6-1.8 kW. The circuit is run separately, 2.5 mm² copper over a short distance or 4 mm² beyond 20 metres, with its own breaker and a surge protection relay. Classes A++ in cooling and A+ in heating mean that over a season of daily duty the machine will use roughly a quarter more than an A+++ model of the same capacity.

Which jobs it fits and where it is out of place

The PC18SQ suits a living room, an office, a shop, a cafe or a workshop of 35-50 m² where both cooling and real heating in the cooler months are wanted and where the outdoor unit is seen and heard by neighbours. The heating bias makes it a sensible choice for an extension, an attic or a space with electric heating that is expensive to run all spring. Where the model is out of place: a bedroom or study where 31 dB(A) from the indoor unit will intrude at night; a space with partitions that a wall unit physically cannot serve; halls with ceilings above 3.5 m. For many hours of daily duty through the whole season, class A+++ such as the H18S1D (item 1802) works out better. And if heating is wanted in frost, that is a job for a Therma V heat pump rather than an air conditioner.

How it differs from neighbouring models in this catalogue

The S18EQ (item 1810) is the same machine without Wi-Fi: output, dimensions, pipework and noise are identical, with control by infrared remote only. The PC24SQ (item 1809) is the larger model of this series at 6.6 kW of cooling and 7.5 kW of heating for spaces up to 70 m², with a 5/8 inch line and a 30 m run. The WZ18AWN (item 1806) is the Inverter Pro of this capacity: almost the same cooling output, but only 5.1 kW of heat and a lighter 11 kg indoor unit. The H18S1D (item 1802) is the Deluxe rated A+++ at 23 dB(A) indoors: quieter and more frugal, but with a 60 dB(A) outdoor unit. The CT18R (item 1836) is a cassette of the same output for a suspended ceiling: a dearer installation, but four-way air distribution with no cold jet in a single direction.

Tell us whether you need heating in the shoulder season and where the outdoor unit will stand, and we will choose between the Wi-Fi and non-Wi-Fi versions and check that 5 kW is enough.