The Siemens Alpha Basis Direct B20502-06N2 wiring centre connects room thermostats and electrothermal actuators in underfloor, wall or ceiling heating and cooling systems for 6 zones. Power supply AC 230 V, protection rating IP20. More information
Delivery to Belgium (days are avarages)
DHL Express: 1.2 workdays, € 16,94
| Power Supply | 230 VAC |
| Weight | 0.45 kg |
Siemens Alpha Basis Direct B20502-06N2 is a wiring centre for controlling underfloor, wall or ceiling heating and cooling. It is used to connect room thermostats and electrothermal valve actuators in individual room temperature control systems – in a 6-zone version. System components can be powered directly from the module, and the thermostats’ switching commands are transmitted to the connected actuators.
The module is designed for installation in heating circuit manifolds – typically in flats and family houses, offices or hotels with underfloor, wall or ceiling heating or cooling. It is suitable wherever you need to control the temperature in each room independently: the living room, bedroom, bathroom or office can each have their own thermostat and valve actuator, while the module provides central coordination, including control of the circulation pump and the heat or cooling source.


The Alpha Basis Direct module supports a wide range of Siemens room thermostats – RAA mechanical thermostats, RDH, RDE and RDL digital thermostats (including wireless sets), RDL211 thermostats for heating and cooling in 2-pipe and 4-pipe systems, RDG200 universal controllers, as well as RDZ thermostats from the Connected Home system. Electrothermal actuators STA321.65L (230 V) or third-party actuators with a max. switching current of 500 mA per actuator can be connected to the valve outputs. A total of up to 15 actuators can be connected to the 6-zone version.
Factory settings and key parameters:
Both versions have the same dimensions (90 × 326.5 × 52 mm) and use the same printed circuit board. In the 6-zone version, the terminal blocks for some zones are not fitted. The 6-zone version can handle a maximum of 15 actuators, while the 10-zone version can handle up to 18 actuators and allows connection of up to 10 thermostats.
Yes. In such cases, the output contacts of the switching units of the wireless thermostats are connected to the module (e.g. RDH100RF/SET, RDE100.1RFS, RDL101RF.ST or RDZ101ZB from the Connected Home system). The switching units can be powered directly from the Alpha Basis Direct module, so no separate power supply is required.
The module supports both heating and cooling. For 2-pipe systems with changeover between the two modes, a condensation sensor (e.g. QXA2100 or QXA2101) can also be connected, which automatically switches off the cooling system if condensation is detected. For 4-pipe systems, heating and cooling can operate simultaneously on separate circuits.
The module is mounted on a TS35 DIN rail (snap-on) or directly on the wall using wall plugs and 4 mm diameter screws. The connection terminals are screwless, and the cables are inserted vertically. The module requires no maintenance. The scope of delivery includes an installation manual in 12 languages.
No. The package contains only the Alpha Basis Direct module itself and the installation manual. Room thermostats, electrothermal actuators (e.g. STA321.65L10) and any limit thermostats or condensation sensors must be ordered separately.
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