Mitsubishi Electric Mr Slim explained

Mr Slim is a name that turns up on a lot of air conditioners in shops, cafés and offices around Central Victoria, and it confuses people because it isn't one product. It is Mitsubishi Electric's light commercial range: a family of indoor units of different shapes, matched to a family of outdoor units, meant for rooms that a standard wall split struggles with.

Mitsubishi Electric's own history page says the Mr Slim name was launched in 1978 for commercial air conditioners. In Australia the company now writes it as MR SLIM and describes the range as wall mounted, ceiling cassette, ducted and under ceiling models for shops, offices and other light commercial jobs.

The indoor units

Each Mr Slim indoor unit has a code that tells you its shape. The ones on Mitsubishi Electric Australia's light commercial page at the time of writing are:

• PLA ceiling cassette, 7.1 to 13.5 kW. Sits in the ceiling with only the grille showing. Good for an open shop floor or dining room where there is no sensible wall.
• PCA under ceiling, 5 to 13.5 kW, plus a stainless steel 7.1 kW model. Hangs under the ceiling and sends air out across the room. Handy where the ceiling space is shallow.
• PKA wall mounted, 7.1 and 10 kW. Mitsubishi Electric describes it as a flat panel design for business interiors. Think of it as a bigger, heavier duty wall split.
• PEAD ducted, 5.0 to 14.0 kW. A low profile ducted unit 250 mm high with a built in condensate pump, rated R32 on its product page.
• PEA ducted, 10.0 to 16 kW across the GAA and HAA models, for larger spaces.

The outdoor units

The indoor unit is half the story. The outdoor unit decides how far the pipes can run, whether it needs single or three phase power, and how well it heats when it is cold outside. Mitsubishi Electric lists three families.

• SUZ-M, 2.5 to 7.1 kW, R32, described as suiting residential and light commercial work. Its guaranteed heating range is minus 10 to 24 degrees outside for the 2.5 and 3.5 kW models, and minus 15 to 24 degrees for the 5.0 to 7.1 kW models.
• PUZ-M, 5.0 to 14 kW, R32, single phase.
• PUZ-ZM, which Mitsubishi Electric calls its Power Inverter, 7.0 to 14.0 kW, R32, in single and three phase (the 7.0 kW model is single phase only). Mitsubishi Electric states a guaranteed heating range of minus 20 to 21 degrees outside, and cooling from minus 15 to 52 degrees, with an optional air protection guide needed below minus 5 degrees in cooling. It also offers longer pipe runs.

For heating in the hills, that PUZ-ZM figure is the one people ask us about. Keep in mind that a guaranteed operating range means the system keeps running at that temperature. It does not mean it puts out full rated heat there, which is why sizing for winter matters.

Where Mr Slim makes sense

We tend to reach for a Mr Slim system in a few situations.

1. Big single spaces. A café dining room, a gallery, a church hall, an open plan living area with high ceilings. Once you need more than a large wall split can give, a cassette or under ceiling unit spreads the air better.
2. Ducting one zone properly. A PEAD ducted unit can serve a suite of rooms or a shop with a back office through ceiling grilles, without a unit on the wall at all. For whole homes we look at full ducted systems instead.
3. Three phase sites. Plenty of commercial buildings in Daylesford and Castlemaine have three phase power. The PUZ-ZM range comes in three phase, which can make the electrical side tidier.
4. Long pipe runs. Heritage shopfronts often have nowhere to put an outdoor unit near the room. The longer pipe runs on the Power Inverter range give us more room to move.

Warranty, and the server room trap

Mitsubishi Electric's support page lists five years parts and labour on P series (Mr Slim) equipment at the time of writing. The same page drops that to one year where the unit is used for a server or communication room, and says the set point in those rooms must be no lower than 24 degrees.

That second line is worth knowing. A Mr Slim wall unit cooling a comms cupboard, a wine room or a back room full of equipment is not being used for people's comfort, and the warranty changes with it. If a room needs steady cooling all year for stock or equipment, it is often a job for proper refrigeration or a system chosen for that duty, and we will say so when we measure up.

How we size it

Every Mr Slim job starts with a site visit. We measure the space, look at ceiling height and construction, glass, insulation, how many people are in it at peak times, what power is available and where the outdoor unit can go. Then we quote the system, and nothing is ordered until you are happy with it. If you have an existing Mr Slim system that has started short cycling, icing up or making new noises, that is a service call on our repairs and maintenance side.

For a measure and quote on a commercial or larger room job, get in touch through our contact page or ring 0417 734 206 between 8:00am and 4:30pm, Monday to Friday.