LG CM24R (24,000 BTU, 7 kW) - medium-static ducted indoor unit 270 mm high

The CM24R: 7 kW medium-static in a 900 mm casing

The CM24R is a ducted indoor unit of LG's R32 semi-industrial series rated at 7 kW cooling and 8 kW heating. The dimensions are 900 mm wide, 700 mm deep and 270 mm high - metal with plastic elements, supply 220-240 V, 50 Hz, with a Dual Inverter compressor in the pair. Per the card the circuit pipework is 1/4 inch (6.35 mm) liquid and 5/8 inch (15.88 mm) gas; the maximum pipe run is 30 metres and the height difference up to 15 metres. The manufacturer country and country of origin are Korea and the warranty 24 months. This is the most interesting model in the series for difficult sites: the same output as the CL24R (item 1827), but with higher static pressure and a narrower casing.

900 mm instead of 1100: where those 200 mm decide it

The CL24R of the same output has an 1100 mm wide casing, while this one is 900 mm wide at 270 mm high instead of 190 mm. In practice that often turns out to be decisive: the unit has to fit between structural beams, into a narrow service void above a corridor, between a ventilation duct and a wall. Where the beam spacing is 1000 mm, an 1100 mm casing physically does not fit, while a 900 mm one goes in with room for the hangers. The flip side is height: if the void above the ceiling is less than 380-420 mm, the gain in width means nothing. The choice between the CL24R and the CM24R is therefore always about both dimensions together, and it should be made from the actual dimensions of the space rather than from a drawing, where beams often do not appear.

Several rooms from one unit

This model's static pressure allows three or four rooms on the same regime to be served: a hotel floor with guest rooms, an office block with individual offices, a medical centre where all the rooms run to the same schedule. The layout is built from a main duct along the corridor with branches into each room, each with its own supply grille and a manual volume damper on the branch. The limitation is the same as on any single-circuit system: one temperature for the whole circuit, with the unit working from the return-air sensor or a remote sensor in a chosen room. That means the rooms have to be alike in load: a room with a south window and a room with a north window on one circuit will sit at different temperatures whatever the setting. The branch dampers are set once at commissioning from actual measurements, and after that the layout works stably.

Fresh air: how much and how

Medium static pressure makes it possible to mix in fresh air without losing output, and for spaces with people in them that often matters more than the cooling itself. The usual benchmark is roughly 30 cubic metres per hour per person for offices and halls; for a room with four workstations that is 120 cubic metres, a noticeable share of a 7 kW unit's airflow. The duct from outside is fitted with a motorised damper, a filter and, in the cold season, preheating or a heat exchanger - without preheating, the indoor coil ices up in winter. The sound solution for a site with people in it continuously is a separate heat recovery ventilation unit, such as those of the LZ-H series, which runs alongside the air conditioning and returns up to 70-80 per cent of the heat from the extract air. If there is no ventilation at all, an air conditioner will not replace it: it cools the same air round and round, and by the end of the day the space feels stuffy at a comfortable temperature.

Drainage: long runs and quiet

A 7 kW unit produces several litres of condensate an hour in hot weather, and its drain line is not a formality but a separate element of the design. The line is run with a constant fall of 1-2 centimetres per metre; on long runs that fall eats up height, and it is often simpler to fit an ABDPG drain pump (item 1914) than to raise the unit 15 centimetres higher. A trap is mandatory: without it, drain odours enter the room, and with the fan running condensate can be drawn up and sprayed about. The drain pipe is insulated just like the refrigerant pipes: water condenses on a cold surface, and leak marks on a ceiling often come not from the drain itself but from an uninsulated drain pipe. Quiet in the room also depends on the drain: a thin plastic pipe with no insulation and no clips transmits the sound of dripping into a plasterboard ceiling, and we meet that complaint more often than complaints about the fan.

Pairing with an outdoor unit

The CM24R pairs with the UU24WR outdoor unit (item 1815) at 7 kW cooling and 8 kW heating, single-phase, in a casing of 950 by 834 by 330 mm. The current of such a system at 220-240 V is roughly 11-13 A, so a dedicated 2.5 mm² copper circuit with its own breaker is needed, along with a check on the headroom in the authorised capacity. The 30 metre run limit and 15 metre height difference open up a wide choice of location for the outdoor unit, but they call for oil traps and an accurate refrigerant top-up calculation. The limit for a pair is always the lesser of the values on the indoor and outdoor cards, and we cross-check that against LG's documentation. We confirm the final combination against the manufacturer's compatibility table - that is a condition of the system's warranty.

Which jobs it fits and where it is out of place

The CM24R is the choice for a space of 60-75 m², or a group of rooms with a combined need of up to 7 kW, where the duct network is long, there is a filter or fresh-air mixing, and the casing has to fit a space under a metre wide. Typical sites: a hotel, an office block, a medical centre, a salon with several areas on one regime, a narrow sales floor. Where the model is out of place: a void of less than 380-420 mm - the CL24R (item 1827) or a cassette is taken there; a simple two-grille layout, where high static pressure is simply not needed; spaces with different temperatures in different zones. A kitchen, a laundry or a workshop with high heat gains needs separate equipment and a separate ventilation calculation. If the requirement exceeds 7 kW, you move to the UM series: the UM36R (item 1830) at 10 kW and above.

How it differs from neighbouring models in this catalogue

The CL24R (item 1827) is the same 7 kW output at 190 mm high and 1100 mm wide: slimmer, but it needs a simpler network. The CM18R (item 1828) is medium-static 5 kW in the same 900 by 700 by 270 mm casing: a step down in capacity. The CL18R (item 1826) is 5 kW low-static. If there is no suspended ceiling, 7 kW is available from the CT24R cassette (item 1837) or the MJ24PC wall unit of a multi-split system (item 1874). The outdoor unit for this model is the UU24WR (item 1815); the same unit works with the CL24R and the CT24R, so the indoor type can be chosen once the location of the outdoor unit has been agreed.

Send us the ceiling void dimensions, the beam spacing and the room layout - we will check whether the CM24R fits and size the network with fresh-air mixing.