25
SAFETY TEMPERATURE BREAKER – STB
Fig.14. a) STB temperature limiter, b) STB with cover removed
The role of the safety temperature limiter STB (fig. 14a) is to disconnect blower
and feeder power supply when the temperature exceeds 95°C on the central
heating system supply pipe. The limiter is installed directly on the boiler, close
to the power supply pipe, as shown on fig. 15a. Having undone 4 screws, the
enclosure lid shall be removed. Next the limiter box shall be installed on the
boiler using 2 screws in openings (W) (fig. 14b). Cables are attached to the
connector (Z) (fig. 14b). the protective line is connected to the terminal
identified as PE. Remaining two lines are connected to terminals C and 2. If
cables connected to terminals C and 2 are exchanged, this will not affect the
controller nor STB operation. On the side of the controller, the cable shall be
connected to terminal strip (8) (fig. 7) terminals identified with the symbol
shown on figure 15b. The protective wire shall be connected to a terminal of the
PE terminal strip (9) (fig. 7). The recommended cross-section of the STB
connection cable is shown in table 1. The STB capillary and the boiler
temperature sensor shall be attached to the supply pipe with the fixing clip
(delivered in the kit) within 10÷15 cm away from the stub pipe or the connecting
flange (fig. 15a). Having performed all of the above tasks, the sensor shall be
thermally sealed with the pipe.
a)
b)
W
W
Z
