VRV/VRF and air conditioners with KNX: gateways, what you can control and how

In short: Air conditioners and VRV/VRF systems connect to KNX through a gateway. There are two ways: one gateway per indoor unit, programmed in ETS and suited to homes, or one central gateway on the outdoor units' bus, which handles dozens of units and suits large buildings. From KNX you control mode, setpoint, fan and vanes, and read temperature and faults. Two things make the biggest difference: temperature from a KNX sensor in the room instead of the unit's own sensor, and switching off when a window opens.

In most Greek homes, air conditioning is the largest load and the most common reason a home "does not feel comfortable". In our article on heating and cooling automation we covered the logic: zones, thermostats and rules. Here we look at the practical question: how KNX talks to your air conditioner.

Two ways to connect

	Per-unit gateway	Central gateway
Where it connects	To the indoor unit or its wired remote bus	To the outdoor units' bus or the manufacturer's central controller
How many units	One	Many, e.g. 4, 16 or 64 Daikin indoor units per HMS gateway
Configuration	ETS, like any KNX device	Usually the gateway maker's software, e.g. Intesis MAPS
Window or presence inputs	Often, on the gateway itself	Via KNX
Best fit	Homes, apartments, small offices	Large homes with VRV, hotels, office buildings

A central gateway also provides information from the outdoor units. The HMS gateway for Daikin, for example, has an algorithm that estimates energy consumption per indoor unit. A per-unit gateway is simpler to program and keeps every room independent.

Gateways by brand

Example products from the manufacturers' catalogues. Compatibility always depends on the unit's series and model.

Brand	Per unit	Central
Daikin (VRV, Sky Air)	Intesis INKNXDAI001R000, on the remote's P1/P2 bus. Zennio KLIC-DI v2	HMS IN770AIR...KNX_DAI on DIII-NET: 4, 16 or 64 indoor units
Daikin (residential)	Zennio KLIC-DD v3, on the indoor unit's S21 port
Mitsubishi Electric	Intesis INKNXMIT001I000 for domestic, Mr.Slim and City Multi (CN105 socket on domestic units)	HMS IN770AIR...KNX_MIT via a central controller (AE-200 etc.), up to 100 groups
Toshiba (VRF, Digital)	Intesis INKNXTOS001R000, with 4 binary inputs	Intesis INKNXTOS064O000, up to 64 indoor units
LG (VRF)	Intesis INKNXLGE001R000	Intesis INKNXLGE064O000, up to 64 indoor units
Samsung (NASA VRF)		HMS IN770AIR00MO000_KNX_SAM, up to 64 indoor units
Panasonic (ECOi, PACi)	Intesis INKNXPAN001R000
Hitachi	Intesis INKNXHIT001R000
Fujitsu General (VRF)		UTY-VKGX, up to 128 indoor units

There are also multi-brand gateways, such as CoolAutomation's CoolMaster range. The older CoolMasterNet has been discontinued. The manufacturer notes that the maximum number of units depends on the VRF brand and that some models need an adaptor.

What you control and read

On Intesis per-unit gateways, for example, the available datapoints are:

• Control: on/off, mode, setpoint, fan speed, vane position, remote controller lock.
• Status: room temperature, error flag and error code, an operating hours counter for filter cleaning.
• Energy saving: open-window function, operating timeout, switch-off when the space is unoccupied.

Two things worth knowing:

1. Setpoint limits differ by unit. On Mitsubishi Electric units, for example, they depend on the unit type. The gateway cannot go beyond what the unit itself allows.
2. Not every unit has every function. The number of fan speeds or an automatic fan speed, for example, depends on the model.

Temperature from the room, not the ceiling

The indoor unit usually measures temperature in the return air, that is high up, near the ceiling. That can differ noticeably from the temperature where you sit. A KNX sensor in the right spot in the room, in a push button or thermostat, gives a more reliable reading. Several gateways can use it:

• Daikin with Intesis: the temperature comes from KNX. The unit must be set by a Daikin technician to the appropriate sensor mode, which not all models support. When the gateway is slave, it "corrects" the setpoint it sends so the room reaches the target.
• Mitsubishi Electric with Intesis: Virtual Temperature Control, with room temperature from a KNX sensor.
• Daikin with Zennio KLIC-DI v2: the external temperature only works when the KLIC is master. If no value arrives for 3 minutes, the unit returns to its own sensor. That is a good safeguard in case of a fault.

Master and slave: the remote stays

In systems such as Daikin VRV, the gateway connects to the same bus as the wired remote (P1/P2). One is set as master and the other as slave, and if there is no remote, the gateway becomes master. So:

• the air conditioner's remote keeps working,
• changes from the remote show up in KNX, and vice versa,
• the master or slave setting affects which functions are available, such as external temperature.

These are set together with the air conditioning technician, which is why involving the VRV installer early saves site visits.

Scenarios worth having

1. Switch off with an open window. A contact or a KNX RF window handle on the window, and the unit switches off after an adjustable delay.
2. Economy when the room is empty. A presence sensor moves the unit to an economy setpoint.
3. "Leaving home": one button at the entrance switches off every air conditioner and lowers the blinds.
4. Working with shading: blinds close against the summer sun so the air conditioning works less.
5. Fault alerts: the error code reaches the app, so the technician knows what to bring.
6. Filter reminders based on operating hours.

Before you buy

1. Model and series of each indoor unit: check compatibility in the gateway maker's list.
2. Per unit or central: how many units you have, and whether it is a VRV/VRF system or standalone air conditioners.
3. Gateway location: inside or near the indoor unit, or in the board for central gateways.
4. KNX cable to each unit. In new construction, see what else to plan from the start.
5. The air conditioning technician available for the unit settings.

How Sync-Teq helps

We connect air conditioning to the home's or building's KNX automation: gateway selection, coordination with the air conditioning installer, temperature and presence sensors, and HVAC energy optimisation scenarios. Contact us with your unit models to see what fits.

Sources

• HMS (Intesis): Daikin VRV and Sky to KNX, INKNXDAI001R000
• Intesis: DK-RC-KNX-1i manual (P1/P2, master/slave, temperature from KNX)
• HMS: Daikin DIII-NET to KNX (4, 16, 64 units)
• Zennio: KLIC-DI v2 manual
• Zennio: KLIC-DD v3 manual
• Intesis: ME-AC-KNX-1-V2 manual for Mitsubishi Electric
• HMS: Mitsubishi Electric City Multi to KNX
• HMS: Toshiba VRF to KNX, up to 64 units
• HMS: LG VRF to KNX, up to 64 units
• HMS: Samsung NASA VRF to KNX
• Fujitsu General: UTY-VKGX KNX Converter for VRF
• CoolAutomation: CoolMaster product line