Ducted reverse-cycle systems provide year-round heating and cooling from a single system — increasingly the preferred choice for Melbourne new builds and major renovations. Because these systems operate in both heating and cooling modes, they have specific cleaning requirements that differ from gas-only heating systems. The indoor fan coil unit — unique to refrigerated cooling systems — is a component that requires its own maintenance attention beyond the duct network clean.
How Ducted Reverse-Cycle Cleaning Differs from Gas Heating
The duct network cleaning scope — supply branches, trunk line, return air duct, registers, filter replacement, and sanitisation fogging — is identical for both system types. What differs is the addition of the indoor fan coil unit cleaning scope in a reverse-cycle service.
The indoor fan coil unit
In a ducted reverse-cycle system, an indoor air handler unit sits in the roof space (or ceiling cavity). This unit contains the evaporator coil — a heat exchanger where refrigerant absorbs heat from the return air during cooling mode. As warm room air passes over the cold coil, moisture condenses on the coil fins (just as a cold drink bottle sweats on a humid day). This condensation makes the fan coil environment permanently moist during cooling operation — ideal conditions for mould and bacteria if not kept clean.
Coil fin cleaning
The evaporator coil fins accumulate a mixture of dust (from return airflow) and biofilm (from the moist coil surface). A fouled coil has reduced heat exchange efficiency — the system runs longer to achieve the same cooling output — and the biofilm on the fins is a continuous source of mould spores being distributed by the fan. Coil cleaning involves brushing the fin surfaces and applying a coil cleaning solution that breaks down organic buildup. The cleaning is done with the system off and must be performed carefully to avoid damaging the thin aluminium fins.
Condensate pan and drain
The condensate pan sits below the evaporator coil and collects the condensation dripping from the coil. A drain pipe carries the condensate from the pan to a drain or to the exterior. Two failure modes affect the condensate system: the drain blocks (typically with algae or debris, causing the pan to overflow and potentially drip through the ceiling) and the pan surface develops mould growth from standing water or residual moisture. Both are addressed during a comprehensive reverse-cycle service.
Seasonal Maintenance Schedule for Melbourne Reverse-Cycle Systems
Pre-summer (October)
Before the Melbourne cooling season begins, a fan coil inspection and clean is the priority: check the condensate drain is clear, clean the condensate pan, brush the coil fins. This prevents the first-start mould smell that is common in systems that have sat inactive over winter. Replace the fan coil filter if due.
Pre-winter (April)
Before the Melbourne heating season: check that the heating operation is functioning correctly, replace the return air filter if due, and consider whether the full duct network clean interval has been reached (every 2 to 3 years).
Full service (every 2–3 years)
Complete duct network cleaning plus fan coil unit cleaning plus condensate pan service plus filter replacement. This is the comprehensive service that covers all maintenance scope for the indoor portion of a Melbourne ducted reverse-cycle system.
Efficiency Impact of a Fouled Reverse-Cycle System
A clean reverse-cycle system operates at its rated efficiency. A fouled system — dusty coil fins, blocked condensate drain, debris-laden duct network — operates at a fraction of its rated efficiency. The coil fouling effect alone can reduce cooling capacity by 15 to 30 percent, meaning the system must run significantly longer to achieve the same result. For Melbourne households where the reverse-cycle system is the primary source of both heating and cooling, this represents a substantial ongoing increase in electricity bills compared to a properly maintained system. See our guide on dirty ducts and energy bills in Melbourne.