Unigas RX92R-FGR, Service Manual

Page: 52 / 125

4
1 WIRING RECOMMENDATIONS
1.1 Earthing
1.1.1 TN earthing system
For the LMV5x-System it is preconditioned that a TN earthing system is used.
In a TN earthing system, one of the points in the generator or transformer is connected with earth, usually the star point in a three-phase system.
TN
− S: PE and N are separate conductors that are connected together only near the power source. This arrangement is the current standard for
most residential and industrial electric systems in North America and Europe.
TN-C-S: Combined PEN conductor from transformer to building distribution point, but with separate PE and N conductors in fixed indoor wiring.
LMV system must be connected to earth (PE). ∆ Volt must be 0 V between N-PE.
NOTE: PE = protection earth, it is not FE
FE = functional earth
1.1.2 Protective Earth (PE) and Functional Earth (FE)
P
rotective
E
arth (PE):
Known as an equipment grounding conductor, avoids hazards by keeping the exposed conductive surfaces of a device at earth potential.
To avoid possible voltage drop no current is allowed to flow in this conductor under normal circumstances, but fault currents will usually trip or blow
the fuse or circuit breaker protecting the circuit.
For example: burner body or the third wire in a 3 wire cable (N L E)
F
unctional
E
arth (FE):
Is not intended for shock protection. It is used for a common reference potential.
For example: cable shields.
N
PE
N
PE
TN-S-earthing
Generator or transformer
Earth
Consumer
TN-C-S-earthing
Generator or transformer
Earth
Consumer
L2
L3
L2
L3
L1
L1