Siemens LMV5 Series Technical Instructions page 36

Technical Instructions
Document No. LV5-1000
Grounds
The LMV5 has three different types of grounds:
Protective Earth
•
Functional Earth
•
Reference Ground
•
Protective Earth
Protective Earth (PE) or chassis ground must always be connected to the control panel grounding lug.
The purpose of PE is to provide a ground for all 120 VAC connections. One wire from the secondary side
of the control panel's main step-down transformer should also be connected to the control panel
grounding lug, as well as a PE on LMV5 transformer terminal SEK2.
All of the PE terminals on the front of the LMV5 casing are common.
Functional Earth
Functional Earth (FE) connections are found on the CANbus terminals as well as other low voltage
connections. The sole purpose of the FE is for termination of low voltage cable shields.
The FE is bonded to the Reference Ground through capacitors on the LMV5 circuit board with the
exception of the CANbus where it is bonded directly.
Reference Ground
The last type of ground is the Reference Ground (0). These are found on the low voltage connections.
The purpose of the Reference Ground is to serve as a datum to measure other voltages.
The Reference Ground is bonded to the FE on the CANbus circuit board through SEK2 pins 2 and 3 on
the AGG5.210 transformer.
Note: AGG5.210 transformer SEK2, pins 2 and 3, are also connected to the control panel grounding lug
(PE), so that all three grounds are eventually bonded together.
Summary:
0 & PE are bonded together at the transformer (connect SEK2 pin 3 to panel ground).
•
For the CANbus only, FE is bonded to 0 & PE directly on the circuit board.
•
Everywhere else, FE is bonded to 0 & PE through a capacitor on the circuit board.
•
Section 2
(marked as PE on the LMV5)
(marked as FE on the LMV5)
(marked as 0, M or GND on the LMV5, hereafter referred to as 0)
Page 2
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