A wired KNX touchscreen thermostat for chilled-water fan coil units, for Dubai villas and apartments built or renovated with a KNX system.
The Siemens RDF800KN is a wired KNX touchscreen thermostat for chilled-water fan coil units. It suits Dubai villas and apartments that already have, or are getting, a KNX system. It is not a Wi-Fi gadget and has no app of its own. It runs on 230V and switches the fan coil directly. It drives a 1-speed or 3-speed fan and one or two valves, using simple on/off or 3-position actuators. That covers 2-pipe, 2-pipe with an electric heater and 4-pipe fan coils, plus chilled ceilings and single-stage compressor units. Two spare inputs take a window contact, a keycard or presence sensor, a return air sensor or a changeover sensor. On the KNX bus it shares room temperature, mode and setpoint, so a keypad, touch panel or home server can control it and run schedules. The thermostat has no weekly timer of its own. You need KNX cable at the back box, a KNX power supply and a programmer with ETS software. Phone control, Apple Home or Alexa need a KNX IP gateway and a visualisation server on top. It fits a UK square back box with 60.3 mm screw centres, at least 40 mm deep, and the front is 86 x 86 mm. The RDF800KN is ivory white and the RDF800KN/VB is black. Do not buy it for a ducted split, VRF or wall split. It also makes little sense in a home with no KNX, because you pay for bus features you never use.
Runs 2-pipe and 4-pipe chilled-water fan coils with up to 3 fan speeds
Shares temperature, mode and setpoint with the rest of your KNX systemWindow, keycard and presence inputs stop cooling empty roomsKeeps every setting through a power cut, with no battery to replaceModel RDF800KN (S55770-T350), RDF800KN/NF (S55770-T335), RDF800KN/VB (S55770-T429)
| Applications | 2-pipe, 2-pipe with electric heater and 4-pipe fan coils; chilled ceilings; 1-stage compressor units |
| Fan output | 1-speed or 3-speed (Q1, Q2, Q3), max 5(2) A at AC 230 V |
| Valve outputs | 2 relay outputs, on/off or 3-position, for AC 230 V actuators |
| Power supply | AC 230 V, 50/60 Hz, live and neutral, max 6 VA |
| Communication | KNX TP1 (S-mode via ETS4 or later, LTE mode with Siemens Synco) |
| Inputs | 2 multifunction inputs: window contact, keycard or presence, remote or return air sensor, changeover, dew point, fault |
| Mounting | Flush on round 60 mm box or square BS 4662 box (60.3 mm centres, 40 mm deep minimum); front 86 x 86 mm |
| Setpoint and sensor | 5 to 40°C in 0.5°C steps; built-in sensor accurate to 0.5 K at 25°C |
| Finish and rating | Ivory white (RDF800KN) or black (RDF800KN/VB); IP30, indoor use 0 to 50°C |
Most Dubai towers and many villas cool with chilled water, often from district cooling providers such as Empower, Emicool or Tabreed. The fan coil in your ceiling takes that water, and the RDF800KN controls its fan and valve. It does not touch the chiller, the plant room or your cooling meter. Before we order, we check three things. The valve actuators must be 230V on/off or 3-position types, not 24V or 0-10V. The back box must be a UK square box with 60.3 mm centres and 40 mm or more of depth, with a neutral present. And KNX cable must reach the thermostat point, which is easy in a new build or full renovation and messy in a finished apartment. In towers, fan coil controls can link to building systems, so tenants need landlord and often building management approval. Mount it about 1.5 m high, away from sun through floor-to-ceiling glass and away from the fan coil's air stream.
Siemens in the UAE. Siemens Smart Infrastructure room thermostats and building controls are specified on UAE villa, hotel and tower projects and supplied through HVAC and building-automation distributors rather than retail shops, so we quote them per project. KNX models need an existing KNX system and commissioning.
