AC Installation & Repair

The job of an air-conditioner is to remove heat at the rate the space gains it, and that rate has two parts. Sensible heat is the energy that changes air temperature — from the sun through glass, the people, the lights, the computers, the hot outside air leaking in. Latent heat is the energy needed to remove moisture — from occupants, from open doors, from the humid coastal air. A unit sized for sensible heat alone leaves a space cold and clammy, which is why "so many BTU per square metre" rules of thumb produce so many uncomfortable, under-dehumidified rooms.

A proper load calculation totals every gain — fabric, solar, occupancy, equipment, lighting, fresh-air ventilation — for the worst design hour, then sizes the equipment to that. In Kenya the design conditions swing from the dry highland cool of Nairobi to the humid heat of Mombasa, so the same room needs a different machine in each city. We calculate rather than guess, because every assumption made with a thumb is paid for daily in either discomfort or wasted power.

The instinct to "buy a size up to be safe" is precisely wrong for air-conditioning. An oversized unit cools the air to the thermostat setpoint so fast that it switches off before it has run long enough to dehumidify— so it short-cycles, leaving the room cold but damp and sticky, while the compressor wears out from constant stop-start. It also costs more to buy and run, and it controls temperature poorly because it is always slamming between full output and off.

The modern answer is the inverter (variable-speed) compressor, which modulates its output to match the load instead of cycling, holding both temperature and humidity steady while drawing far less energy at part load — where the system spends almost all its life. A correctly sized inverter system beats an oversized fixed-speed one on comfort, electricity bill and lifespan, all at once.

The refrigerant inside the system is now a regulatory decision as much as a technical one. Under the Kigali Amendment, which Kenya has joined, high global-warming-potential (GWP) HFCs are being phased down. The old R410A(GWP ~2,088) is giving way to lower-GWP options like R32 (GWP ~675) and, in some equipment, natural refrigerants such as R290 (propane, GWP ~3, but flammable and tightly charge-limited). Buying R410A equipment today is buying into a refrigerant whose supply and price will only worsen over the machine's life.

The trade-off matters: lower-GWP refrigerants are often mildly flammable (ASHRAE class A2L) or flammable (A3), which drives charge limits, room-size rules and installer competence requirements. We specify refrigerant with the phase-down and the safety classification in mind, so the system is both legal and serviceable for its full life — not stranded in five years when the gas becomes scarce.

Air-conditioners are rated by how much cooling they deliver per unit of electricity consumed. EER is that ratio at a single rated condition; SEER is a seasonal average that rewards good part-load behaviour (which is why inverter units score well); and COP is the same idea expressed as a pure ratio of cooling output to electrical input. A unit with an EER of 3.5 delivers 3.5 kW of cooling for every 1 kW of power — the rest is "free" heat moved rather than generated.

Because cooling is often a building's single largest electrical load, the gap between a cheap low-EER unit and an efficient one repays the price difference quickly. We size first, then choose the highest sensible efficiency for the duty, and on solar-equipped sites we time the cooling to the array's daytime output — the cheapest cooling is the cooling run on your own solar power.

The architecture follows the building. Split and multi-split units suit single rooms and small offices — simple, cheap, independently controlled. VRF/VRV (variable refrigerant flow) shines in medium-to-large commercial buildings with many zones of differing load, moving refrigerant to dozens of indoor units from a compact outdoor plant and even shifting heat from a sunny side to a shaded one. Chilled-watersystems with central chillers and air-handling units are the workhorse of large buildings, hospitals and industry, where their capacity and water-side flexibility outweigh their complexity.

The decision weighs zoning needs, building size, maintenance access and the cost of downtime — a hospital theatre and a four-room SACCO office have nothing in common but the word "air-conditioning." We design ventilation (fresh-air rates to ASHRAE 62.1) and filtration into the same plan, because comfort without adequate fresh air is just recirculated staleness, and indoor air quality is part of the brief whether or not it appears in it.