Air conditioning installation in Dartford

What actually gets fitted?

Two boxes and a connection. The indoor one is slim and mounts high on the wall of the room being treated; the outdoor one, which holds the compressor, stands on feet or a bracket outside. Linking them are two lagged copper pipes carrying refrigerant, a control cable and a narrow drain for the water the indoor coil condenses out of humid air. On a Dartford semi with the bedroom over the kitchen, a single hole through the back wall carries the lot and the outdoor unit sits a metre below the window. Front rooms and upper-floor flats are where the skill lies: the run may have to drop down a side wall in trunking, cross a ceiling void or finish on a flat roof.

What happens on the survey visit?

We walk the route before anyone talks money. The room is measured for floor area and ceiling height, and we note which way its glass faces, because a north-facing box room and a west-facing loft with two rooflights ask for different capacities. We ask who owns the outside wall: the freeholder of a block, a landlord, or on an Ebbsfleet or Castle Hill estate a management company holding covenants. We stand where the outdoor unit would go and judge the sound at the closest neighbouring window or door. We check whether the condensate can drain by gravity or needs a small pump, and we open the consumer unit to see whether a spare way exists for a new circuit. The written price follows, and if the building rules the job out we tell you then, not after a deposit.

Who does the wiring, and why is it a separate line?

A registered electrician, because English law says so. Adding a circuit to a dwelling is notifiable under Part P of the Building Regulations, so it has to be done by someone on a competent person scheme, or be certified afterwards by a registered third party. The IET names the schemes: BESCA, Blue Flame Certification, NAPIT, OFTEC and Certsure, which covers NICEIC and ELECSA. The work is the fused spur indoors and a weatherproof isolator beside the outdoor unit, and Checkatrade puts the national cost at £400 to £700. The certificate matters when you sell: solicitors ask for it. Sources: IET; GOV.UK; Checkatrade.

How do we know the system is sound before it runs?

By testing it twice before any refrigerant goes in. First the joined pipework is filled with nitrogen under pressure and left to prove it holds. Then a vacuum pump draws the circuit down to remove air and moisture, which would otherwise corrode it from inside. Only after both does the engineer release the refrigerant, and releasing it is work that the law reserves for someone with an F-gas qualification. Most new units run on R32, which burns under some conditions, so a very small room is checked against the safety standard before a model is chosen. The system is then run in both cooling and heating with thermometers on the air, and the controls are explained before we go. Sources: GOV.UK; Energy Saving Trust.

What decides the price of an installation in Dartford?

Three things in order: the capacity the room needs, the length and difficulty of the pipe route, and how we reach the outdoor position. A ground-floor room with the outdoor unit on the patio directly behind it is the cheapest configuration there is. A third-floor flat at Ebbsfleet whose only outdoor position is a flat roof, or a terrace where the unit must stand at the end of the garden, needs more pipe, more hours and sometimes a tower. For a national marker, Checkatrade lists £750 for a 12,000 BTU wall unit and £1,150 to fit it; add those two and you get about £1,900 before the electrics. The cost guide works through each extra, and our air conditioning in Dartford page explains why the building, not the room, so often sets the figure here. Source: Checkatrade.