Cable Length - Siemens FS20 Planning Manual

7.1.7 Cable length

7.1.7.1 Cable resistance
Building Technologies
Fire Safety
Additional cabling
● FDnet alarm devices (e.g., alarm sounder FDS221) are also connected to the
↑ detector line and do not need a separate supply line. Power supply is
ensured by the detector line.
● Detector heating units cannot be connected to the FDnet detector line. They
must be operated via a separate supply line.
● The input/output module FDCIO223 always requires a separate 24 V power
supply.
● The following devices can be operated via the FDnet or a separate, electrically
isolated supply line:
– ↑ Floor repeater terminal FT2010-A1, FT2010-C1
– ↑ Floor repeater display FT2011-A1
– Mimic display driver FT2001-A1
NOTICE
Influencing the earth fault monitoring
Faults
● There must be electrical isolation of the supply unit for devices on the FDnet
that are fed separately.
The maximum permitted ↑ detector line length is 3300 m. The permitted length
may also be limited by the following factors:
● Cable resistance
● Cable capacitance
The cable resistance and cable capacitance depend on the cable type used. This
must be considered in planning.
The cable length that is relevant for the capacitance calculation may differ from
that necessary for the resistance calculation.
The relevant values are the cable resistance of each of the two ↑ loop connections
up to the detector that is furthest away.
LOOPxA
LOOPxB
Figure 22: Max. cable resistance (max. R) to the farthest detector
Planning detector lines
Planning an FDnet detector line
max. R
max. R
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2015-12-15