What is a split air conditioner?
The word "split" puzzles a lot of people the first time they see it on a quotation. It simply describes how the equipment is arranged. Instead of one box doing everything, as with a window unit or a portable machine on wheels, the system is divided in two. One half sits inside the room and moves air. The other half sits outside the building and gets rid of the heat. A pair of insulated copper pipes and a cable link them together through a small hole in the wall.
Nearly every fixed air conditioner fitted in British homes and businesses today is some form of split. This guide explains what each half does, the different split types you will come across, and how to work out which layout fits your building.
The two halves and what they do
The indoor unit contains a coil, a fan, a filter and the controls. Warm room air is drawn across the coil, where cold refrigerant absorbs its heat, and cooler air is blown back into the room. Moisture in the air condenses on that coil too, which is why every indoor unit needs a small drain pipe.
The outdoor unit holds the compressor, which is the heart of the system, along with a second coil and a large fan. The compressor squeezes the refrigerant, raising its temperature, and the outdoor fan blows air across it so the heat collected indoors is released outside. Because the compressor and big fan are the loudest components, putting them outdoors is what makes a split so much quieter in the room than a portable unit.
Reverse the flow of refrigerant and the whole process runs backwards, pulling warmth from outdoor air and delivering it indoors. That is why every system we fit is a heat pump and heats in winter as well as cooling in summer.
Mono split: one indoor, one outdoor
The simplest arrangement pairs one indoor unit with one outdoor unit. It is sometimes called a single split or mono split. It suits a single bedroom, a home office, a small shop or one meeting room. If one part fails, only that room is affected, and each outdoor unit can be sized precisely for its space.
Multi-split: several rooms, one outdoor unit
A multi-split connects two or more indoor units to a single outdoor unit. Each room keeps its own remote and temperature setting. The attraction is fewer boxes on the outside wall, which matters on terraced streets, flats and period properties. The trade-off is that the rooms share one compressor, so if the outdoor unit develops a fault, every connected room loses cooling at once.
Indoor unit styles within a split
- Wall-mounted: the familiar slim unit high on a wall. Quick to fit and the most common choice in homes.
- Ceiling cassette: sits flush in a suspended ceiling and blows air four ways. Popular in shops, restaurants and offices.
- Ducted: hidden in a ceiling void or loft, with only grilles showing. Ideal where appearance matters or during a renovation.
- Floor or console: sits low on a wall, useful in conservatories or under sloping loft ceilings.
Where VRF fits in
Variable refrigerant flow, often shortened to VRF or VRV, takes the multi-split idea further. One outdoor plant can serve many indoor units across a whole floor or building, adjusting refrigerant to each zone. It is a commercial solution for larger offices and multi-room premises rather than something a typical house needs.
Split system or portable unit?
Portable machines keep the compressor inside the room, so they are noisy, and they vent warm air through a hose hung out of a window, which lets heat and insects back in. They are a stopgap. A split system is fixed, quieter, more efficient and far better at holding a steady temperature, though it does need a proper installation by an F-Gas qualified engineer because refrigerant is involved.
How to choose the right layout
Start with how many rooms need cooling and whether they are used at the same time. Then think about where an outdoor unit could sit without bothering bedrooms or neighbours, and whether the look of the indoor unit matters. A free site survey answers these properly: Ted McCarthy Services measures up, suggests positions and pipe routes, and follows up with a written quotation. We fit Panasonic, LG and Midea equipment across Hertfordshire, Buckinghamshire, Bedfordshire and London from our Hemel Hempstead base.
FAQs
Common questions
Why is it called a split air conditioner?
Because the system is split into an indoor unit and an outdoor unit connected by refrigerant pipes, rather than housed in one box.
Is a split air conditioner the same as a heat pump?
The systems we install are heat pumps: the same split system can reverse to heat a room in winter as well as cool it in summer.
Can I install a split system myself?
No. Connecting and charging the refrigerant circuit must be done by an F-Gas certified engineer. Our installers are Refcom certified.
How far can the outdoor unit be from the indoor unit?
It depends on the model, which is why positions and pipe routes are agreed at the survey before a quotation is written.
Keep reading
More from our knowledge base
System & comparison guides
Domestic vs Commercial Air Conditioning: The Real Differences
Short answer: a home usually needs quiet wall units sized room by room, while a business needs equipment chosen for longer hours, more people and legal record keeping.
Fault & symptom guides
Air Conditioning Not Cooling Properly
A unit that runs but never quite cools the room is one of the most common calls we get, and the cause is rarely the compressor.
Fault & symptom guides
Air Conditioning Smells Musty
A sour, damp smell when the AC kicks in is almost always biological growth on the indoor coil, not a fault with the refrigeration circuit itself.
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