Achievable Cable Length With Lsn 1500 A - Bosch FPA-5000 System Description

Modular Fire Panel
3.7

Achievable Cable Length with LSN 1500 A

The usable cable length depends essentially on the resistance of the cable and the quantity
and current consumption of the network elements.
The way in which the elements are distributed locally on the bus also makes a difference. The
possible cable length can be estimated using the formula (1). This formula is also used in the
FSD (Fire System Designer) calculation program and is based on the critical application
situation where all network elements are concentrated at the end of the bus line. The
calculated cable lengths are therefore on the conservative side.
The diagrams on pages Page 38 and Page 39 can be used to make a quick estimate.
L =
The following applies:
L = cable length to be calculated in [m]
U
0
U
End
q = cable cross section = 0.503 mm
n
E
ρ= specific resistance of copper = 0.0178 mm
R
FET
I
NE
I
trans
I
flash
For technical reasons the cable length must not exceed 3000 m. Note that the non-isolated
cables for network elements must not exceed a total length of 500 m and must be included in
the maximum cable length of 3000 m.
The 500 m limit applies to the following interface modules in the FLM-420 series (with non-
isolated inputs).
FLM-420-RHV, FLM-420-I2, FLM-420-I8R2, FLM-420-O8I2, FLM-420-O1I1, FLM-420-RLE.
Using the Diagram for LSN improved
FET resistance = 0.35 Ω, fire alarm cable with ∅ 0.8 mm
Example 1:
You want to know the maximum cable length for a given number of network elements and a
given current consumption (n
you reach the 0.5 mA curve. Then, from the point of intersection go horizontally to the left to
the Y axis and read off the maximum achievable cable length. In this example it is 1950 m.
Example 2:
You want to know the maximum number of network elements for a given cable length
(L = 1000 m, I
as far as the 2 mA curve and then from the point of intersection vertically down to the X axis.
Read off the maximum number of network elements, in this example it is 73.
NOTICE!
Remote alarm indications activated by the detector C point:
A maximum additional cable length of 500 m is allowed when using remote displays (e.g.
MPA/FAA-420-RI).
The total length of installed cable must not exceed the limit of 3000 m.
Bosch Sicherheitssysteme GmbH
º
q U − U − n × R
0 END E
2 Ó (n
E
= bus voltage at the connection terminals = 30 volt
= bus end voltage = 15 volt (must not fall below this limit!)
= number of elements
= FET resistance = 0.7 Ω (LSN classic) or 0.35 Ω (LSN improved),
= average current consumption of elements in [A]
= transmission current = 0.012 A
= flash current = 0.018 A
= 2 mA). Starting from the Y axis at 1000, go horizontally across to the right
NE
À
Æ Æ É É
⁄
n − 1 2 × I + I
FET E NE
É
× I + I + I
NE trans flash
2 (for cable ∅ 0.8 mm)
2
/m)
= 120, IN = 0.5 mA). On the X axis, go vertically up at 120 until
E E
System Description
Planning | en
(1)
½
Ã
+ I
trans flash
F.01U.028.089 | 8.0 | 2011.07
37