MSA 47K Series, Operation Manual

Page: 13 / 52

GB
MSA INSTALLATION
Series 47K Gas Detector [SIL 2]
13
3.5. Electrical Connection to the Control Unit
3.5.1 Junction Box Terminals
Screw terminals: cross section 0,5–2,5 mm
2
Spring terminal: cross section 0,5–1,5 mm
2
3.5.2 Maximum Cable Length
The maximum cable length depends on the maximum permissible load, the cross
section of the conductor and the conductor material.
The maximum permissible load [loop resistance] is 36 ohms for the MSA Control
units SUPREMA [for MSA Control unit 9010/9020 refer to the control unit
manual].
Maximum cable length: L =
R x k x A
2
L = cable length in metres [loop]
R = maximum permissible load in ohms
A = cross sectional area of conductor in mm
2
k = conductivity of copper at 20 °C [1/Resistivity]
Example: R = 36 ohms, A = 0.75 mm², k = 56 m ohms
-1
mm
-2
L = 36 x 56 x 0.75/2 = 756 m
Wire Cross
Section Maximum Load
[max. cable resistance]
Maximum
Length Remarks
0.75 mm² 36 Ohm 750 m
Screened cable
is required.
1.5 mm² 36 Ohm 1,500 m
For detailed information refer to the relevant MSA controller manual.