Air conditioning for homes, offices and shops

A single split system has one outdoor unit connected by refrigerant pipework to one indoor unit, usually high on a wall. A multi-split runs two or more indoor units from one outdoor unit, which saves space outside but means all rooms depend on one compressor. Larger homes and offices sometimes use ducted or ceiling cassette units instead.

Portable units with a hose through the window need no installer, but they are noisy, less efficient and leak warm air back in through the window gap. A fixed system is quieter indoors because the compressor sits outside.

Size matters in both directions. An undersized unit runs flat out and never catches up on a hot afternoon; an oversized one cycles on and off and dehumidifies poorly. The installer should size each room from its floor area, glazing, orientation and how many people and computers are in it, not from a rule of thumb.

Most air conditioners contain fluorinated gases. By law, anyone installing, servicing, leak-checking or recovering refrigerant from these systems must hold the right personal F-gas qualification; a category 1 certificate covers all activities. The company must also hold an F-gas company certificate from an approved body such as Refcom, F-Gas Register (Quidos) or Bureau Veritas, which has to be renewed periodically.

That rules out fitting a split system yourself and asking an engineer to 'just gas it up'. Pre-charged DIY kits exist, but the refrigerant circuit is regulated work, and a poorly made joint leaks refrigerant and ruins the efficiency. Ask for the company's F-gas certificate number and check it with the certification body.

Because a reversible air conditioner moves heat in both directions, it can heat a room in winter more efficiently than a direct electric heater. The Boiler Upgrade Scheme in England and Wales now offers a smaller towards an air-to-air heat pump, but only where the system replaces fossil fuel heating such as gas, oil, LPG or direct electric, is installed by an MCS-certified installer and is designed to heat the whole home.

MCS excludes systems that only cool, and systems optimised for cooling rather than heating. At the time of writing MCS says it is still bringing air-to-air heat pumps into its scheme, so ask any installer directly whether they are MCS certified for air-to-air systems before counting on the grant. Air-to-air units do not heat your hot water, so you will need another way of doing that.

Source: gov.uk

The outdoor unit is where most permission questions arise. Permitted development rights for air source heat pumps in England are tied to microgeneration standards, so do not assume they cover a unit installed mainly for cooling. Ask the installer to check whether your position needs planning permission, especially on a flat, a listed building, in a conservation area or on a wall facing the road.

Leaseholders usually need the freeholder's consent to fix anything to the outside wall or run pipes through it. Noise matters too: an outdoor unit under a neighbour's bedroom window will cause complaints even if it is allowed. The indoor unit also needs a condensate drain, either by gravity to a gully or through a small pump, and a dedicated electrical circuit in many cases.

In England and Wales, any air conditioning system with an effective rated output of more than 12kW must be inspected by an accredited energy assessor, with inspections no more than five years apart. The duty sits with whoever controls the system, often the tenant of a shop or office rather than the landlord. The inspection report is one of the energy certificates you can arrange through the government's find an assessor service.

Businesses that operate air conditioning also have leak-checking and record-keeping duties under the F-gas rules depending on how much refrigerant a system contains. Your service contractor should tell you which apply.

Source: gov.uk

• the make and model of indoor and outdoor units, cooling and heating output, and the refrigerant used
• how each room was sized
• outdoor unit position, bracket or ground mount, and noise at the nearest window
• pipe route, pipe length included in the price and the condensate drain
• electrical supply and whether a new circuit is needed
• the F-gas company certificate number, commissioning and leak test
• servicing interval and warranty conditions

Tell us how many rooms need cooling, roughly how big they are and whether the system should heat as well. After you confirm your phone number by text-message code and your email by link, the request is offered anonymously to air conditioning companies in your area. Only one company can buy it; it pays Offrano, and the listing is then removed. You pay us nothing.

We send you that company's name, address and phone number by email before it sees your details, and you can withdraw consent from any of our emails. There is no promise that a company takes the request; unsold requests are withdrawn after 21 days. You do not have to accept any quote. Offrano checks that buyers are registered businesses, not their F-gas status or workmanship, so check that yourself.