Ducted zoning explained

A ducted system has one indoor unit, in the roof or under the floor, and one fan pushing air through ducts to outlets around the house. Without zoning, every outlet gets air whenever it runs. Heat the main bedroom at 10 pm and you heat the lounge and the empty study too.

Zoning splits the ducts into groups of rooms, with a motorised damper in the duct feeding each group. The Victorian Government recommends zones for ducted systems as the more efficient option, because each zone can be heated on its own rather than the whole home at once.

That matters more with ducted than with a wall split. The Australian Government notes ducted systems aren't as efficient as wall units, because they use a larger fan and lose energy through the ductwork. Sending air only to the rooms you're in claws some of that back.

Dampers sit near where the ducts branch off the main supply box. Each is a blade inside a short length of duct, turned by a small motor. They live in a roof space that swings from freezing to baking, so motors and linkages wear, and a zone that won't open or won't shut is a common fault.

A zone module, a small control board, drives the motors and takes its instructions from your wall controller or app. On newer systems it also tells the indoor unit how many zones are open, so the unit can ease back. Many older setups can't. The dampers move, but the unit runs as if the whole house wanted air.

Controllers differ too. Some only switch zones on and off, while others give each zone its own temperature and timer. Find out which kind you have before blaming the system.

Most comfort complaints come back to one question: where is the thermostat? In many older installs the sensor sits in the return air grille, often in a hallway, or inside the wall controller. The system runs until that spot reaches the set temperature. If the hallway warms quickly, the unit backs off while the far bedrooms are still cold.

Basic on/off zoning works this way. You pick the open zones, but one sensor sets the temperature for all of them. Temperature-controlled zoning puts a sensor in each zone, and each damper opens part-way or closes as its zone reaches its own setting, so the lounge can run warmer than the bedrooms.

The Victorian Government suggests 18 to 20 °C for heating and 24 to 26 °C for cooling living areas, and says each degree beyond that adds around 10% to running costs. Room sensors read truest on an internal wall, away from sun, outlets, ovens and televisions.

A ducted unit is built to move a set volume of air and needs a minimum amount moving. Shut most zones and the fan forces that air into a couple of rooms' worth of duct. Outlets roar, and the coil can run too cold in cooling or too hot in heating until the unit's own protection shuts it down.

Good zone design allows for this, with a common zone that never closes or a spill damper that bleeds off surplus air when a small zone runs alone. Lots of small zones look flexible on the controller, but each extra split makes airflow harder to manage.

Dirty filters add to it. The Australian Government's Energy Rating site notes they significantly reduce airflow and efficiency, and can affect heating. A clogged return air filter plus one small zone is a familiar cause of a system cutting out on cold nights.

Zoning pays off when parts of the house are used at different times: living areas from late afternoon, bedrooms overnight, a study during the day. Victorians typically use more energy for heating than cooling, so winter counts most. Laverton's long-term average July minimum is 5.2 °C, and heating just the bedroom zone on those nights is zoning doing its job.

Summer matters too, with Laverton averaging 27 days a year at or above 30 °C. In a double-storey home the upstairs usually heats up faster, so a zone for each level, ideally with its own sensor, stops one floor being overcooled to suit the other.

YourHome notes that zoned systems cool only occupied areas and allow different conditioning in living and sleeping areas. That only happens if you use the zones. Leave every zone open all day and the dampers are just extra parts.

Zoning moves air around. It doesn't add capacity. The Victorian Government suggests 1.1 to 1.4 kW of heating output for every 10 m² a ducted system covers, depending on the home. A unit well short of that will struggle with every zone open. Zoning lets it do fewer rooms properly, not the whole house on the coldest nights.

Ducts are the other usual culprit. YourHome says they should be insulated to at least R1.5, with joints sealed to prevent condensation and leakage. A duct that has slipped off its fitting, been flattened in the roof or lost its insulation leaves a room cold whatever the controller says. That's a ductwork repair, not a zoning one.

Some layouts don't divide. An open-plan kitchen and family area with no doors is one zone, because the air mixes. A single small room such as a home office often can't take enough air on its own, and a split system there can be the simpler answer.

Plenty of gas ducted heaters have zone dampers, and many without them can have zones added, depending on the heater, its controls and the duct layout. With floor vents the ducts usually run under the house, so underfloor access becomes part of the assessment.

Energy Safe Victoria says it's illegal, and potentially fatal, for unlicensed and unqualified people to do any gasfitting or electrical work. Dampers and controls are duct and control-wiring work, and anything on the gas side belongs with a licensed gasfitter. Adding refrigerated cooling is different again: in Victoria, an add-on condenser unit for a ducted system is refrigerated air-conditioning work, a class of plumbing work.

Energy Safe Victoria also recommends servicing ducted gas heaters every two years, with a carbon monoxide test at the heating vent outlets in all rooms. On a zoned heater that means opening every zone for the test, including rooms you rarely heat.

Before anyone climbs into the roof, sketch the house and mark who uses which rooms, and when. Group rooms that are used together and face the same way. A west-facing lounge sharing a zone with a south-facing bedroom means one of them is always uncomfortable. Allow for a future nursery, office or extension too.

It makes sense to get Total Comfort in when a zone stops responding, outlets turn noisy or the unit keeps cutting out, or when you want zones added or are replacing a ducted system. Our technicians check the unit, ducts and controls together, because a zoning complaint is often one of the other two in disguise. Where the job includes electrical installation work, the electrician must give you a Certificate of Electrical Safety.

Quotes are free and no-obligation, and you get the price before we start. If the honest fix is a moved sensor or a new damper motor, that's what we'll tell you.