On most ducted systems the filter sits behind the return air grille in the ceiling, and several brands leave it to your installer. Here's where to find it, how to wash it without warping it, and what seven brands' own documents say about how often: anywhere from every two weeks to every 12.
Where the filter is on a ducted system
On a wall split, the filter sits behind the front panel. A ducted system has no front panel in the room. The air comes back to the unit through a big grille in the ceiling, the return air grille, and on most systems the filter sits behind it.
Daikin puts it simply: the filter sits behind the return air grille in the ceiling, often in a hallway. Some units carry their own filter instead. Mitsubishi Electric's PEAD units have one at the air intake of the indoor unit, and you lift its knob to pull it out.
Some manufacturers do not supply the filter at all. Rinnai's ducted manual says the filters are supplied and fitted by your installer and are not part of the Rinnai system.
Mitsubishi Electric's high static manual lists no filter among the unit's parts. Its large ducted units ask for an optional or locally bought filter at the air inlet. Fujitsu sells one as an optional kit for its high static units.
So the filter in your ceiling may not carry the brand on the outdoor unit. Mitsubishi Heavy Industries says it outright: the filter goes in when the system is installed, so ask the company that installed it how to take it out and clean it.
Why the filter matters
The manuals agree on what a dirty filter does. Mitsubishi Electric says airflow drops when the filter is dirty or clogged. Mitsubishi Heavy Industries adds that the system loses capacity, wastes electricity and runs louder. Rinnai says a clogged filter increases running costs and shortens the life of the unit.
They also agree on one rule: do not run the system with the filter out. ActronAir, Daikin, Mitsubishi Electric and Mitsubishi Heavy Industries all say it.
Rinnai's warranty booklet adds one more reason. It lists regular filter cleaning among the things the owner has to do during the warranty period.
How often: what each brand says
The calendar as a table
| Brand | Cleans in a year | What the document says |
|---|---|---|
| Rinnai | 26 | Inspect and clean at least every two weeks (operation manual, Issue E) |
| Daikin | 8 | Every month in peak summer and winter, the start of each season otherwise (its guide, quoting Energy Star) |
| ActronAir | 4 | Every 12 weeks, or when the filter light shows (owner’s manual) |
| Mitsubishi Heavy Industries | 2 | At the ends of the cooling and heating seasons, and when the message shows (user’s manual) |
We read the documents for the ducted ranges we install. Here is what each one tells you about the filter.
| Brand | Where the filter is | How often to clean it | Filter reminder |
|---|---|---|---|
| ActronAir | Behind the return air grille | Every 12 weeks, or when the filter light shows. More often in a dusty home | A FILTER light on ActronAir wall controllers |
| Daikin | Behind the return air grille in the ceiling | Every month in peak summer and winter, and at the start of each season otherwise. Daikin quotes this from Energy Star, and its own tip is a reminder every two to three months | A filter clean reminder is listed among its controller features |
| Fujitsu high static | An optional filter kit | Not given in the manual we read | A filter sign your installer can set to 1,250, 2,500 or 4,400 running hours. It is off when the unit leaves the factory |
| Mitsubishi Electric PEAD | On the indoor unit, at the air intake | No interval given | Not listed for this unit |
| Mitsubishi Electric high static | None supplied: the parts list shows no filter | No interval given | Not listed for this unit |
| Mitsubishi Electric large ducted | An optional or locally bought filter at the air inlet | Follow that filter's own instructions | Not listed for this unit |
| Mitsubishi Heavy Industries (FDU, FDUM) | Fitted when the system is installed | When the "Filter cleaning" message shows, and at the end of summer and winter | A "Filter cleaning" message after a set running time |
| Rinnai | Supplied and fitted by your installer | Check at least every 2 to 4 weeks, and the cleaning page says every two weeks | Not mentioned |
| Samsung S2 | Not covered | The user manual has no filter section | Not covered |
The spread runs from every two weeks to every 12. The calendar above shows what each one adds up to in a year. If your controller has a filter reminder, go by that. On a Fujitsu system, though, the reminder stays off unless your installer switched it on.
Carrier, LG, Panasonic and Toshiba are not in the table, because we could not get their current ducted owner's manuals. For those, the manual that came with your unit is the one to follow.
How to clean it
The steps are the same across the manuals that give them:
- Switch the system off at the controller first.
- Use a steady stepladder, and mind your eyes: dust can fall as the grille opens.
- Open the grille and take the filter out.
- Vacuum it, brush it, or tap it against something solid.
- If it is very dirty, wash it in lukewarm water with a mild detergent, then rinse it well.
- Keep the water under 50 degrees, or the filter can warp.
- Let it dry fully in the shade, not in the sun or near a heater.
- Put it back before you switch the system on, and reset the filter light if you have one.
Disposable filters are different. Rinnai says to replace those with new ones of the same grade and size, not wash them. It also suggests keeping a spare, so the system is not off while one dries.
What a service does that you cannot
The filter is the part you can look after yourself. Even so, ActronAir's manual recommends new filter material every 12 months, at the yearly maintenance.
Mitsubishi Heavy Industries goes further. Its manual says that after several seasons, the unit needs inspection and maintenance beyond routine cleaning, and that this takes specialist skills.
Our maintenance service checks the filters along with the coils, the drain, the refrigerant and the electrics. On a ducted system, our deep clean goes further: the return air grille and filter, the fan coil, the ducts and the outlets.
If you also have wall splits, their filters are a different job, and our mould guide covers it. For the systems themselves, see the ducted ranges we install.
Can't find the filter, or the grille won't open? Book a service. The filters are part of every one.
Sources
- ActronAir, R-32 Ducted Systems Owner's Manual, Doc. 9590-8000 Ver. 2, June 2022: the 12 week interval, the filter light, the cleaning steps, the yearly filter material and the rule against running without filters.
- Daikin Australia, Cleaning air conditioner filters: updated 27 August 2025. Where the ducted filter sits, the monthly and seasonal interval it quotes from Energy Star, its two to three month reminder, washing and drying.
- Daikin Australia, Ducted Systems brochure PCDUAU0126: the filter in the return air grille and the filter clean reminder.
- Fujitsu General, Installation Manual ARTH24/30/36KHTA, Part No. 9381386345-02: the optional filter kit and the filter sign settings.
- Mitsubishi Electric, PEAD-M JAA(D) operation manual: the filter at the unit's air intake, cleaning, the 50 degree limit, drying and keeping the filters installed.
- Mitsubishi Electric, PEA-M HAA operation manual: the parts table for the high static range, which lists no filter.
- Mitsubishi Electric, PEA-M180 to 250 LAA operation manual: the optional or locally procured filter at the air inlet.
- Mitsubishi Heavy Industries, User's Manual PSA012B820B (FDU, FDUM): the filter fitted at installation, when to clean, how to wash and dry, the reset, and the inspection after several seasons.
- Rinnai, Ducted Reverse Cycle Inverter Operation Manual, Issue E: linked from Rinnai's page for its 17 kW ducted unit. Installer-fitted filters, the two and 2 to 4 week checks, washing, disposable filters and a spare.
- Rinnai, Air Conditioning Warranty Booklet, December 2025: regular filter cleaning among the owner's responsibilities.
- Samsung Australia, user manual AC***TNH*KG, DB68-08478A-01: the S2 ducted manual, which has no filter section.
