Commercial air conditioning

Load, and why commercial gains are different

A domestic room’s cooling load is mostly solar gain plus a couple of people. A commercial space adds several categories that dominate the calculation:

• Occupancy density. A meeting room holding twelve people is a substantial heat source, and it is intermittent – which matters for zoning as much as for sizing.
• Equipment. Every watt of electricity consumed by computers, tills, displays, refrigeration cabinets and kitchen equipment becomes heat in the room. In a server or comms room, this is essentially the entire load.
• Lighting, less than it was with LED, but not zero in a large retail unit.
• Fresh air. Commercial ventilation rates are set by occupancy, and every cubic metre of outside air brought in has to be conditioned.
• Glazing. Large commercial glazing with poor solar control can dominate everything else on a south or west elevation.
• Internal gains that vary by zone. The reason a single-zone system in a multi-aspect building never satisfies everyone.

The characteristic failure is a building conditioned as one zone when it behaves as four. The north side is cold while the south side is warm, occupants fight the controls, and the system runs hard achieving general dissatisfaction.

System types for commercial buildings

For most Norfolk commercial buildings the practical range is multi-split for small premises and VRF for anything with multiple zones or floors.

What we do

• Design and load calculation, zone by zone, from actual gains rather than floor area.
• Installation, including pipework routing through occupied buildings, which is usually the hardest practical part.
• Maintenance contracts, with frequency matched to duty and environment – see planned maintenance.
• F-Gas leak checking and record keeping where the system’s CO2e requires it – see F-Gas compliance.
• Repairs and leak location on existing systems.
• Decommissioning and refrigerant recovery at end of life, with the records the regulations require.
• Taking over systems installed by others, starting with an asset survey so we know what is actually there.

Installation in an occupied building

The technical design is the easier half. Installing into a trading building is where the planning goes.

1. Survey with the building in useActual occupancy, actual equipment, actual glazing behaviour at the times of day that matter.
2. Zoning strategyAgreed against how the building is really used, including the rooms whose occupancy is intermittent.
3. Route surveyRefrigerant pipework, condensate drainage, power and controls all need routes. In a building with a shallow ceiling void or no risers, this determines what is achievable.
4. Outdoor plant locationStructural capacity, access for maintenance, noise to neighbours and to your own occupants, and airflow clearances. Noise is the one that generates complaints.
5. Phasing and out-of-hours workingCore drilling, ceiling access and commissioning are disruptive. Most of it happens outside trading hours.
6. Pressure test, evacuate, chargeNitrogen pressure test, proper vacuum held and verified, then charge by weight and record it. The charge figure is needed for F-Gas purposes.
7. Commission, balance and documentEvery zone tested, controls configured, and an operating and maintenance record handed over.

Noise and planning, in a commercial context

Commercial plant is larger and runs longer than domestic, and noise is the issue that most often turns into a formal complaint. The considerations:

• Planning permission is more frequently required for commercial plant than domestic, particularly on roofs, in conservation areas or where a change of use is involved. Local authorities commonly attach noise conditions.
• Environmental health can act on noise as a statutory nuisance regardless of planning, and a condenser running at night next to residential property is the classic case.
• Acoustic assessment may be required at planning stage, typically comparing plant noise to the existing background at the nearest noise-sensitive receptor.
• Mitigation exists – acoustic enclosures, attenuators, anti-vibration mounts, night setback modes and, most effectively, siting the plant somewhere else.

It is far cheaper to resolve this at design stage than after a complaint. The cost of relocating roof plant retrospectively is considerably more than the cost of an acoustic assessment beforehand.