Question
To control a 4-pipe fan-coil unit over KNX, three Group Objects are typically used: a fan speed (DPT 5.010 or DPT 5.001), a cooling signal and a heating signal (both DPT 5.001 for the valves).
Answer
True
Standard 4-pipe FCU configuration: fan speed on DPT 5.010 (pulse counter 0-255) or 5.001 (0-100%), internally mapped onto 3-5 discrete speeds; cold valve on DPT 5.001 (0-100% opening of the chilled-water valve); hot valve on DPT 5.001 (same for the hot-water valve). An interlock inside the controller must prevent the cold and hot signals from being commanded simultaneously.
Preparation tip
Always validate the cold/hot interlock at commissioning by forcing both signals to 100% in the ETS test mode — discovering the interlock is missing on a real heatwave is painful.
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