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3.3.2. Loop Test
If the wiring is correct and the supply voltage of the circuit
under test is between 195V and 270V the lower indicators will
all indicate green and one of the top indicators marked LOOP
TEST will indicate the range into which the measured earth loop
impedance falls.
For example if the top centre indicator is green then the
measured earth loop impedance of the circuit under test is
between 1.7Ω and 5Ω, or if the top left-hand indicator is red then
the measured earth loop impedance is between 10Ω and 100Ω.
Refer to the latest edition of the IET Wiring Regulations (BS
7671), to determine if the indicated earth loop impedance of the
wiring under test meets the necessary requirements.
Figure 3. Loop Test Indicators (Top LED's)
9
0 - 1.7Ω
1.7 - 5Ω
5 - 10Ω
10 - 100Ω
100 - 200Ω
200 - 500Ω
Wiring fault or voltage
<195V or >270V
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