Sizing a reversible air conditioner: kW, SEER, SCOP and cold weather

Cooling capacity: the starting range

For a properly insulated home, count 80 to 100 W of cooling capacity per m². Go up to 120 W per m² for a heavily glazed room, one facing south or under the roof, and for shops with internal heat gains (lighting, machines, customers). A 15 m² bedroom is fine with a 2.6 kW unit; a 40 m² south-facing living room needs 5 kW.

Oversizing costs as much as it does in heating: the unit reaches the set point too quickly, dehumidifies poorly and cycles. Take the right capacity and let the inverter modulate.

Heating with the air conditioner: look at the heating capacity and the SCOP

An air-to-air heat pump delivers several times the electricity it consumes. The SCOP gives this ratio over a heating season: a SCOP of 4.0 means 4 kWh of heat for 1 kWh of electricity. For heating use, compare:

• The nominal heating capacity, often slightly higher than the cooling capacity.
• The SCOP, more meaningful than the SEER for winter use.
• The minimum outdoor operating temperature in heating mode. Nordic is rated down to −35 °C, Pro Heat+ and most wall-mounted units down to −25 °C, Air and Evo down to −20 °C, the cassettes, floor-standing units and multi-split outdoor units down to −15 °C. The operating limit says nothing about the capacity that remains: look at the capacity at −7 °C or −15 °C on the product page.

Below zero, the capacity delivered drops. A unit rated at 3.4 kW at +7 °C outdoors no longer delivers the same at −10 °C: the manufacturer's ErP sheet gives the capacity at the reference temperature.

Noise level, the argument that gets forgotten

An indoor unit rated at 22 dB(A) on low speed is inaudible in a bedroom; at 40 dB(A), it can be heard. The outdoor noise level matters for the neighbours and for the municipal regulations: an outdoor unit at 50 dB(A) near a neighbour's bedroom is a problem. The values are on the product page when the manufacturer publishes them.

Mono-split or multi-split

One mono-split per room remains the most efficient solution and the easiest to service. A multi-split (one outdoor unit for 2 to 5 indoor units) saves space on the facade and a wall penetration, but imposes strict compatibility between the outdoor unit and the indoor units, and a maximum pipe run per circuit. Check the manufacturer's combination tables before ordering; we check them with you.

R32 refrigerant and F-Gas

All Kaisai splits and multi-splits run on R32, a refrigerant with a reduced GWP (675). The portable air conditioners use R290, in a factory-sealed circuit. The technician who installs a split must be certified for refrigerants: below 3 kg of charge, category II (A2 in the new European nomenclature) is enough; from 3 kg upwards, category I (A1) is required. R32 is classified A2L, mildly flammable: respect the minimum room area given in the manual, which depends on the charge and the mounting height of the unit.

What we need to propose a configuration

Floor area and orientation of each room, insulation, use (cooling only or heating), distance between the indoor units and the location of the outdoor unit, and the noise level wanted. We reply with a configuration and a net price within 24 hours on working days.