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Voltage Drop Measurements
There are three tests within the voltage drop menu.
Measurement
Icon
Voltage Drop at 15-Amp load
Voltage Drop at 12-Amp load
Voltage Drop at 20-Amp load
The National Electrical Code recommends 5% as the maximum voltage drop
for branch circuits for reasonable efficiency (NEC article 210-19. FPN 4).
High voltage drop could be an indication of a high resistance connection
within the circuit, undersized wire for the load or length of run, or a defective
device on the branch circuit.
All of the voltage drop measurements are taken under an actual 12-Amp load
and extrapolated for 15 amp and 20 amp measurements. This allows the
user to test a 15-Amp rated circuit at full capacity or 80% capacity, and test a
20-Amp rated circuit under a full capacity. Voltage drop under a 15 amp
load is the first measurement within this menu selection. Pressing the side
arrow button (→ ) moves the unit from measurement to measurement within
the line voltage menu. Pressing the down arrow button (
↓
) moves the unit
to the next menu selection – Ground-Neutral Voltage.
Troubleshooting Tips
Measurement Expected Problem Possible Possible
Result Causes Solutions
Voltage Drop <5% High - Too much load - Redistribute the
voltage on the branch load on the circuit
drop circuit
- Undersized wire - Check code
for length of run requirements and
re-wire if
necessary
- High resistance - Locate high
connection within resistance
the circuit or at the connection/device
panel and repair/replace
Ground-Neutral Voltage Measurement
There is only one test within the Ground-Neutral Voltage menu. In a single-
phase circuit, high ground-neutral voltage indicates excessive leakage
between the neutral and ground conductors. In a 3-phase circuit with a
shared neutral, a high ground-neutral voltage could also indicate unbalanced
load between the three phases, or harmonic distortion on the shared neutral.
A reading of less than 2 Volts usually indicates a usable outlet. An excessive
ground-neutral voltage may result in inconsistent or intermittent equipment
performance. Pressing the down arrow button (
↓
) moves the unit to the
next menu selection – Line Impedance.
Troubleshooting Tips
Measurement Expected Problem Possible Possible
Result Causes Solutions
Ground-Neutral <2V High G-N - Current leaking - Identify source of
Voltage voltage from neutral leakage (multiple
to ground l bonding points)
- Unbalanced - Check load balance
3-phase system and re-distribute load
- Harmonic content - Oversize neutral or
returning on neutral de-rate transformer
in 3-phase system to dissipate heat
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