KJF-B03 Air Conditioning Companion
The Legom KJF-B03 Air Conditioner Companion is a central air conditioning ion purifier designed to be installed directly inside the return air outlet of an existing central air conditioning system. Unlike standalone fresh air units or ceiling-mounted ventilators that require dedicated installation space, ducting, and active management, the KJF-B03 is hidden entirely within the AC return air grille — occupying zero floor space, producing zero audible noise, consuming only 20W, and operating fully automatically by starting and stopping with the air conditioner itself.
The KJF-B03 uses ion-catalytic dual purification to eliminate bacteria and viruses, remove PM2.5, adsorb dust, smoke, and pollen, and generate negative ions that circulate through the entire space served by the central air conditioning system. With no filter consumables to replace and no user interaction required after installation, the KJF-B03 is the lowest-friction air quality upgrade available for any space already served by central air conditioning.
Key Benefits — The Four Zeros
- Zero consumables – Ion-catalytic purification requires no replaceable filter media. No cartridges, bags, or filter elements to purchase, stock, or replace throughout the unit’s service life
- Zero space – The unit is installed inside the existing central AC return air outlet grille, completely hidden from view and occupying no floor, wall, or ceiling space in the served room
- Zero noise – The KJF-B03 has no moving parts of its own. It operates silently within the air conditioning duct, with no fan motor, no compressor, and no mechanical noise contribution to the indoor environment
- Zero operation – Automatically starts and stops with the central air conditioner. No switches, timers, apps, or user interaction required after installation — purification is simply always active whenever the AC is running
- Near-zero power consumption – At only 20W, the KJF-B03 adds negligible energy cost to the air conditioning system’s operating load. Annual energy consumption at 8 hours per day is approximately 58 kWh
- Ion-catalytic dual purification – Eliminates airborne bacteria and viruses through ionization, removes PM2.5 and fine particles through catalytic capture, and adsorbs dust, smoke, and pollen drawn through the return air stream
- Negative ion health benefits – Negative ions generated by the purification process circulate through the space with the conditioned air, supporting relaxation, stress relief, improved sleep quality, and enhanced immune function through their effect on human cell activity and the nervous system
- Covers up to 600m³/h air flow – Compatible with central AC systems delivering return air volumes up to 600m³/h, covering a wide range of residential and light commercial installations
Technical Specifications
| Parameter | Specification |
|---|---|
| Model | KJF-B03 |
| Rated Power | 20W |
| Rated Voltage | 220V / 50Hz |
| Air Volume Compatibility | 0 – 600 m³/h |
| Noise | Zero (no moving parts) |
| Dimensions | 667 × 118 × 88mm |
| Weight | 3.6 kg |
| Installation Location | Central AC return air outlet |
| Purification Technology | Ion-catalytic dual purification |
| Consumables | None |
| Operation Mode | Automatic (starts/stops with AC) |
Application & Use Cases
- Central air conditioning systems in residential buildings – Apartments, villas, and homes with ducted central AC systems where the return air grille provides the installation point, enabling whole-room air purification without any visible addition to the room’s interior
- Office environments with ceiling cassette or ducted central AC – Adding ion-catalytic purification to existing office AC systems without procurement of standalone units, installation of new infrastructure, or staff interaction to maintain operation
- Hotel rooms and serviced apartments – The zero-operation design means guests never need to interact with or manage the purification system. It simply operates whenever the room AC is in use, without controls, indicators, or maintenance requirements visible to occupants
- Retail and hospitality spaces – Continuous ion-catalytic purification of high-foot-traffic spaces without occupying display or service area with standalone air purifier units
- Medical and clinical waiting areas with central AC – Reducing airborne bacteria, virus, and allergen load in shared waiting environments by leveraging the existing air circulation infrastructure of the central AC system
- Upgrade of existing central AC installations – The most cost-effective path to adding air purification in any space that already has central AC — no new infrastructure, no duct modifications, no visible additions to the room
Installation Notes
- The KJF-B03 is installed inside the return air outlet of the central air conditioning system. Before ordering, confirm that the return air grille dimensions and duct depth are compatible with the unit’s 667 × 118 × 88mm body
- Access the return air duct by removing the existing return air grille. The KJF-B03 is fitted into the duct opening behind the grille, then the grille is reinstated over the unit — completely concealing the purifier from view
- Connect the unit to a 220V / 50Hz power supply. It is recommended to wire the unit to the same circuit as the central AC system so that it activates and deactivates automatically with the AC
- No duct modifications, drilling, or structural work is required beyond access to the return air grille and routing of the power supply cable
- Verify that the return air volume of the central AC system falls within the 0–600m³/h compatibility range of the KJF-B03
- Maintenance consists of periodic removal and cleaning of the ion-catalytic module — no consumable replacements are required. Access is through the return air grille
- Do not install in supply air outlets or in locations where the unit is exposed to direct water spray or condensation drip from the AC evaporator
Frequently Asked Questions
What makes the KJF-B03 fundamentally different from all other Legom air purification products?
Every other Legom air purification product — the XFQT-60-01S, XFDD2-400/500-01JP, XFDD2-650-01J, and XFDD3-360-01JP — is a standalone unit that introduces fresh outdoor air into the space, requiring its own installation footprint, duct connections, and active management. The KJF-B03 is not a fresh air unit at all. It is an add-on purifier that installs inside the return air outlet of an existing central AC system, purifying the recirculated indoor air without introducing outdoor air and without any visible presence in the room. It leverages the existing AC infrastructure entirely, requiring nothing but a power connection and a compatible return air outlet.
Does the KJF-B03 also provide fresh outdoor air?
No. The KJF-B03 purifies the air that is already circulating through the central AC system — it does not introduce outdoor fresh air. It removes PM2.5, bacteria, viruses, and allergens from the recirculated indoor air stream and generates negative ions that distribute through the space with the conditioned air. If CO2 dilution through fresh air supply is also required, a separate fresh air ventilation product such as the XFQT-60-01S or XFDD2-400-01JP should be considered alongside the KJF-B03.
How does the automatic operation work?
The KJF-B03 is wired to activate and deactivate with the central air conditioning system. When the AC is running, the unit powers on and begins ion-catalytic purification of the return air stream. When the AC shuts off, the unit also shuts off. No separate switch, timer, app, or remote control is required — the purification system simply mirrors the AC’s operating schedule automatically.
Can the KJF-B03 be installed in any central AC return air outlet?
The KJF-B03 is designed for central air conditioning return air outlets and is compatible with systems delivering up to 600m³/h of return air volume. Before installation, verify that the return air duct depth behind the grille is sufficient to accommodate the 88mm depth of the unit body, that the opening dimensions match the unit’s 667 × 118mm footprint, and that the return air volume falls within the 0–600m³/h range. Contact the Legom team to verify compatibility for your specific AC system model.
What maintenance does the KJF-B03 require?
The unit has no consumable filter media. Maintenance consists solely of periodically removing the ion-catalytic module through the return air grille and washing it with water to remove accumulated particles. The cleaning interval depends on local air quality and AC operating hours. After cleaning and drying, the module is reinstalled and the unit is immediately ready to operate again.
OEM & ODM Customization
Legom supports OEM and ODM services for the KJF-B03 Air Conditioner Companion series. Our engineering team can customize dimensions, specifications, and branding to match specific central AC system return air outlet configurations. All customization projects are handled with strict confidentiality. Contact us via WhatsApp or info@legomsmart.com.
User Manual
Product information last reviewed by the Legom Technical Team. For the most current specifications, refer to the official datasheet or contact our sales team.
Custom OEM & ODM Solutions
Legom is a direct manufacturer offering end-to-end OEM and ODM services. With our in-house engineering and production capabilities, we work closely with distributors and system integrators to deliver fully customized solutions under strict NDA.
