Monthly for the parts that grow things, quarterly for the service visit, annually for the full service. AS/NZS 3666.2, the microbial control standard, has the outdoor air intakes and exhausts, air filters, humidifiers, coils, trays and sumps, and condensate drains, tundishes and traps inspected monthly and cleaned or replaced where necessary; fans and evaporative cooling equipment three-monthly; ductwork, terminal units and grilles annually. Recommended practice, from AIRAH DA19 and the Standara library, is a quarterly service visit covering filters, condensate drains and coil condition, a six-monthly outdoor unit and condenser coil clean, and an annual full service with a coil clean and controls check. Refrigerant leak inspection follows the system's manual or, where it is silent, AS/NZS 5149.4's recommended intervals: every twelve months for systems with 3 to 30 kg of refrigerant, six months above 30 kg, three months above 300 kg.
The intervals
| Interval | What happens | Who |
|---|---|---|
| Monthly | Inspect, and clean or replace where necessary, the outdoor air intakes and exhausts, air filters, humidifiers, coils, trays and sumps, and condensate drains, tundishes and traps (AS/NZS 3666.2). On a small split system this is the owner's filter clean. | Owner or staff for split systems; mechanical contractor for plant |
| Three-monthly | Fans, and evaporative cooling equipment including the sump, wetted pads and water strainer (AS/NZS 3666.2). Recommended practice (DA19): the quarterly service visit covering filters, condensate drains and coil condition. | Mechanical contractor |
| Six-monthly (recommended practice) | Outdoor unit and condenser coil clean; controls and set points checked before the heating and cooling seasons. | Mechanical contractor |
| Annual | Ductwork, terminal units and their coils, and return and relief air grilles (AS/NZS 3666.2). Recommended practice: the full service with coil clean, controls check and refrigerant charge check. | Mechanical contractor |
| Refrigerant leak inspection | At the frequency in the system's manual; where the manual is silent, AS/NZS 5149.4 recommends every 12 months for hermetic systems up to 6 kg and other systems over 3 kg up to 30 kg, every 6 months over 30 kg up to 300 kg, every 3 months over 300 kg, and after repair or when a leak is suspected for smaller systems. | Technician holding a refrigerant handling licence |
Who does it and what to keep
A mechanical contractor for the plant; the owner for the monthly filter clean on small split systems. Only a technician holding a refrigerant handling licence may open the refrigerant circuit, and a system is not recharged until the leak is found, repaired and leak tested, with the charge added recorded. The record is the service report for every visit with the AS/NZS 3666.2 inspection items ticked and any cleaning noted, the refrigerant service record showing leak inspections, repairs and charge added, and for larger plant the water treatment and cooling tower records that sit with it.
The rule behind the interval
AS/NZS 3666.2 Air-handling and water systems of buildings: Microbial control, Part 2: Operation and maintenance, sets the monthly, three-monthly and annual inspection intervals. AIRAH DA19 HVAC&R Maintenance is the industry guideline the quarterly and annual service visits follow. AS/NZS 5149.4 Refrigerating systems and heat pumps: Safety and environmental requirements, Part 4: Operation, maintenance, repair and recovery, sets the leak inspection recommendation, and the Ozone Protection and Synthetic Greenhouse Gas Management legislation makes the refrigerant handling licence law.
Common questions
Does a small split system need a contractor?
For the monthly filter clean, no; that is the owner's job and the one that keeps the unit efficient. The quarterly or six-monthly service, the outdoor coil clean and anything involving refrigerant need a licensed technician.
How often should the refrigerant be topped up?
Never as a routine. A system that needs topping up has a leak, and under the licence rules it is not recharged until the leak is found, repaired and tested. The leak inspection interval depends on the size of the charge.
Put it in the register
An interval only holds when the asset is listed with its tasks, its contractor and where the record lives. Standara's library carries this asset with the tasks above attached, so adding it to a site's register produces the year's schedule, the monthly to-do list and the completion record the auditor or insurer asks for. The fuller picture, with the neighbouring assets and the rule behind each interval, is in the HVAC maintenance schedule.
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- A worked example: one club's register, planner and records for a year
- All guides and answers