Case Studies

2 Fluke Corporation Instant power replay solves a breaker trip
Zooming into the initial region
of the event in Figure 2, we see
the turn-on loads of the temper-
ature chamber’s dual compres-
sor system. The first compressor
turns on with a large initial
surge, followed by the second-
ary compressor surge. This load
profile clearly identifies the tem-
perature chamber as the cause of
the overload.
Temperature chamber peak
current is 49.7 amps. In Figure 3,
the sustained load is near
25 amps.
We can zoom in further,
in Figure 4, to see even more
detailed resolution of this ini-
tial current surge. Note that the
phase A voltage sags during this
current surge, but the voltage
drop is small, indicating that the
power feed at the sub-panel is
very stiff, and can accommodate
substantial demand.
Conclusion
The power feed to the second
floor is robust. The nuisance
tripping is most certainly due to
temporary overload of a standard
20 amp appliance branch circuit
from using an industrial tempera-
ture chamber on the circuit. The
temperature chamber should be
connected to a dedicated branch
circuit, sized to meet the require-
ments of the chamber, minimum
20 amps.
Figure 2. Compressor activity
Figure 4. Interpreting voltage drop
Figure 3. Load evaluation
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©2007 Fluke Corporation. Specifications subject
to change without notice. Printed in U.S.A.
11/2007 3185343 A-EN-N Rev A
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