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across the breaker. If the voltage drop exceeds 5% but noticeably decreases as you nearer the
panel, the circuit may have undersized wire, too long of a cable run, or too much current on the
circuit. Check the wire to ensure that it is sized per code and measure the current on the branch
circuit. If a voltage drop reading changes significantly from one receptacle to the next, then the
problem is a high impedance point at or between two receptacles. It is usually located at a termi-
nation point, such as a bad splice or loose wire connection, but it might also be a bad receptacle.
Troubleshooting Tips for Voltage Drop
Measurement
Voltage Drop
Estimated Load on Line (ELL) Measurement
The SureTest estimates the load on a branch circuit to provide an indication of how much capac-
ity in the circuit remains or to quickly check if the circuit is dedicated. This function is a rough
estimate (no stated accuracy), as accurately measuring circuit current has to be done with a clamp
meter at the electrical panel. The proprietary way in which these calculations are made allows the
user to plug the unit into an outlet and quickly determine the current load on that branch circuit.
Both the distance of the SureTest from the load and branch circuit impedance will affect accuracy.
Best accuracy is obtained by positioning the SureTest in the same outlet as the largest load on
line; otherwise, try to position the SureTest between the load(s) and the electrical panel. The maxi-
mum amperage reported by the tester is 15A.
ASCC Measurement
The SureTest calculates the Available Short-Circuit Current (ASCC) that the branch circuit can
deliver through the breaker during a bolted fault (dead-short) condition.
The ASCC is calculated by dividing the line voltage by the circuit's line impedance (hot + neutral).
Depressing the side arrow (
neutral, ground) are shorted together -- the neutral and ground provide a lower impedance via
a parallel return path. Note that this second test will trip a GFCI. See the following equations for
clarification.
ASCC 1 = Line Voltage (V HN )/ (Hot Ω + Neu Ω)
ASCC 2 = Line Voltage (V HN )/ (Hot Ω + 1/(1/Neu Ω+ 1/ Grd Ω)
Expected
Problem
Result
High Voltage
<5%
Drop
) displays the worst-case scenario where all three conductors (hot,
Possible
Causes
Too much
load on
the circuit.
Undersized wire for
length of run.
High resistance
connection within
the circuit or at
the panel.
6
Possible
Solutions
Redistribute the
load on
the circuit.
Check code requirements
and re-wire if necessary.
Locate high
resistance connection/
device and
repair/replace.
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