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21
Operation
4. Press the
TEST
button. The GFCI should trip and the display ‘trp’ or display the trip current in mA if it is
between 5-6 mA.
If the GFCI fails to trip, >11 mA is displayed.
Trips at <5 mA
Trips between 5-6 mA
5. The test should be repeated on both 0º and 180º leading half cycle to ensure the GFCI is compliant. This can
be changed by pressing the function key (insert image).
Touch voltage display
The voltage to which an ground conductor may rise during a GFCI test. The limit for touch voltage is 50 V AC or
25 V AC, depending on the environment.
Touch voltage is caused by excessive resistance in the ground circuit when a load is placed between the live and
ground conductors.
Touch voltage is displayed:
- at the end of an GFCI test if the voltage is below the safe limit
- before an GFCI test is started if it would exceed the safe limit.
X
Touch voltage limit
Measured touch voltage
GFCI Trip time (no trip)
GFCI Type
GFCI Test mode
Touch voltage is calculated using the nominal trip current of the GFCI x Ground resistance. For example:
GFCI trip current = 6 mA
Ground resistance = 1000 Ω
0.006 A x 1000 Ω = 6 V
If the calculated touch voltage is less than the Touch voltage limit, the GFCI test will proceed. If it is greater than
the limit set, the test is halted.
The touch voltage limit is set in “Touch voltage display” on page 21 - UL 25 V, 50 V, 60 V
Measurement methods and sources of error
GFCI Testing - Method of measurement
A two wire lead, or mains plug lead should be used for this measurement. A constant current source is connected
across the supply and increased in incremental steps. When the GFCI trips, the current flowing is recorded and
displayed in mA.
GFCI Testing - Possible sources of error
Measurement results can be affected by the following:
Significant operating errors can occur if loads, particularly rotating machinery and capacitive loads, are left
connected during tests.
A poor connection to the circuit under test.
