LG UU18WR (18,000 BTU, 5 kW) - outdoor unit of a semi-industrial R32 inverter system

The UU18WR: 5 kW and a new casing size

The UU18WR is the outdoor unit of an LG R32 semi-industrial system with a circuit output of 5 kW cooling and 5.8 kW heating. At this capacity the casing changes: 870 by 650 by 330 mm instead of the 770 by 545 by 288 mm of the smaller models, so brackets and clearances have to be recalculated. The supply remains single-phase, 220-240 V, 50 Hz, the compressor is a Dual Inverter and the refrigerant R32. The manufacturer country and the country of origin on the card are both given as Korea, which is typical of LG's semi-industrial range. The unit weight is not stated on the card; the residential outdoor module in the same casing weighs 38 kg, and that is the sensible figure to base the fixings on, confirming it against the data sheet before installation.

What a 5 kW circuit can do

Five kilowatts of cooling is no longer one room but a small group of spaces: two offices with a corridor, a hall of 45-50 m², a meeting room with a reception. In a ducted scheme one unit is connected to three or four grilles and distributes air across several rooms, which for an office works out better than three separate wall units. There is an important limitation: a ducted system holds one temperature for the whole circuit, so if one office holds one person and another holds six, the difference in comfort will be noticeable. Different temperatures in different rooms require separate circuits or a multi-split system, for instance based on the MU3R19 (item 1854) with three indoor units. The cassette option at 5 kW serves one space, but distributes air evenly four ways, which in a square room is more comfortable than a ducted scheme with two grilles.

A CL18R or a CM18R ducted unit: a question of static pressure

At 5 kW the catalogue has two ducted units of identical output but different casing heights: the CL18R (item 1826) at 190 mm and the CM18R (item 1828) at 270 mm. The difference is not in cooling but in external static pressure: the low casing is designed for short ducts, the taller one for a branched network with several grilles and longer runs. The practical criterion is simple: if the total duct length from the unit to the furthest grille exceeds 5-6 metres, or the system has more than three bends, the higher-static unit is chosen. A second reason to choose the CM18R is a need for a higher-grade filter or for fresh-air mixing, since the filter's extra resistance also eats static pressure. If the ceiling cannot accommodate 270 mm, the CL18R remains with a hard limit on duct length, and that limit is better accepted at design stage than discovered after installation.

A Dual Inverter on long shifts

In semi-industrial equipment a Dual Inverter compressor with two compression chambers matters less for comfort than for service life: it spends most of its time at part load and does not cycle on and off at full current. For a site where the machine holds temperature eight to twelve hours a day, the number of starts per season differs by an order of magnitude from the old on-off scheme, and it is starts that wear the mechanics most. The second practical advantage is temperature stability in a room full of people: with no swings of two or three degrees, the sensation of alternating heat and cold draught disappears. The third is the ability to run at reduced output on cool days, when the space needs only slight dehumidification and cooling. The flip side of inverter equipment is the board's sensitivity to voltage fluctuations, so in a commercial space a protection relay is not an option but part of the installation.

Installing an 870 by 650 mm unit

A unit of this size hangs on brackets rated for at least 80-100 kg, with through-fixings into load-bearing material and vibration mounts under the feet. Clearances: 70-100 cm in front, 40-50 cm above, 20-30 cm behind and at least 30 cm on the service panel side, because without that access replacing a board turns into dismounting the unit. On the ground the unit stands on a frame raised 30-40 cm, leaving space beneath for condensate to drain in heating mode. The run between the units needs evacuation, a nitrogen test and torque control on the flare joints; maximum lengths and pipe diameters come from LG's combination table for the chosen pair. The indoor drain in a ducted scheme is planned with a fall and an inspection hatch - it is the one point in the system that will need regular attention later.

Electrics

The supply is single-phase, 220-240 V, 50 Hz; at full cooling a 5 kW circuit draws roughly 1.6-1.8 kW, that is 7-8 A. The circuit is run separately: 2.5 mm² copper up to 20 metres, 4 mm² beyond that, with its own breaker and a surge protection relay. In a space with heavy equipment - a kitchen, a compressor, a welding bay - it is worth checking for voltage sags when they start: the inverter board responds to those with faults that look like a broken machine. The outdoor unit's card gives no energy class, because it is determined by the pair: the same UU18WR with a ducted and with a cassette unit will show different seasonal figures. We provide the rated pipe and run data and the classes together with the proposal for a combination.

Which jobs it fits and where it is out of place

The UU18WR is chosen for a space or group of spaces of 40-50 m² where the equipment has to be hidden in the ceiling and run from a wired controller: an office, a clinic, a salon, a shop, a meeting room with a reception. It is also the basis for a scheme with a ducted unit distributing air to several grilles, which wall units fundamentally cannot do. Where the model is out of place: as a separate product without an indoor unit - the system does not work; in a space with no spare height above the ceiling - a ducted unit simply will not fit; in rooms with differing temperature requirements - separate circuits are needed. For a large hall of 70 m² one 5 kW circuit is too little: that points to the UU24WR (item 1815). And if the main aim is to cool one room cheaply, a residential 5 kW wall unit is far simpler to install.

How it differs from neighbouring models in this catalogue

The UU12WR (item 1813) offers 3.5 kW in the more compact 770 by 545 mm casing: a simpler installation, a smaller circuit. The UU24WR (item 1815) offers 7 kW in a 950 by 834 mm casing: a taller unit again and new demands on space. The CL18R (item 1826) is the 5 kW ducted indoor unit, 190 mm tall, for short ducts. The CM18R (item 1828) is a ducted unit of the same output, 270 mm tall, for a branched duct network. The CT18R (item 1836) is a cassette of 570 by 570 mm and 256 mm in height, the option for a single square room; the UV18R (item 1842) is a ceiling-suspended unit 1200 mm wide for when there is no suspended ceiling at all, and it is often what saves the day in spaces with exposed services.

Send us a floor plan and the spare height above the ceiling, and we will say whether a ducted or cassette unit pairs with the UU18WR, and whether the static pressure covers the number of grilles you need.