Bus Cabling - Siemens OpenAir G..B181.1E/KN Series Technical Basics

Formula for cable
length
Example: Power
consumption and
permissible voltage drop
(1 VAV controller)
Example: Parallel
connection of
4 actuators
22 / 44
Siemens
Building Technologies
The following formula can be used to calculate the maximum cable lengths.
Permissible voltage
Operating voltage
drop per line
AC 24 V 4 % of AC 24 V
A Cross-sectional area in [mm
L Permissible cable length in [m]
P Power consumption in [VA] or [W];
refer to the actuator's type field
Operating Power
voltage consumption
AC 24 V 3 VA
Determine the cable lengths for 4 actuators operating on AC 24 V. Decisive for
sizing the cable are only the AC currents on lines 1 (G) and 2 (G0). Maximum
permissible voltage drop = 4 % per line.
∂ Consumption = 4 x 3 VA = 12 VA
∂ Line current = 4 x 0.125 A = 0.5 A
Permissible single cable length for G and G0:
∂ 164 m with a cross-sectional area of 1.5 mm
∂ 274 m with a cross-sectional area of 2.5 mm
4.2.2

Bus cabling

Instructions regarding topology and addressing in KNX networks can be found in
the documents [13] and [16]. The following sections presuppose electrical
installations that conform to the KNX-TP1 standard
VAV compact controller KNX/PL-Link G..B181.1E/KN
Formula for cable
length
1313 ∂
L =
2
]
Perm. voltage drop for line...
1 (G), 2 (G0)
4 % of AC 24 V
2
2
A
Ζm∴
P
CE1P3547en
2017-03-23