Application Note

2 Fluke Corporation Monitoring power usage: five reasons to log power and energy use
Fluke Corporation
PO Box 9090, Everett, WA 98206 U.S.A.
Fluke Europe B.V.
PO Box 1186, 5602 BD
Eindhoven, The Netherlands
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©2013 Fluke Corporation.
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Printed in U.S.A. 8/2013 6000862A_EN
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being used when, by what, and
at what hourly cost. Without fail,
the data will turn up several
energy wastes that can be
rectified by operational changes
alone, such as turning off certain
loads, reducing loads during peak
rate periods, or adjusting the
schedule so that loads operate
during non-peak rate periods.
3. Accuracy of electrical bill
Owners of large and medium
sized facilities often install elec-
trical sub metering to bill tenants
for their specific electricity usage.
However, these sub meters are
commonly installed improperly,
putting that billing into ques-
tion. Installation issues vary, from
current transducers installed
backwards, current transducers
on the wrong phase, and errors
in configuring the sub meter.
A good business practice is to
double check the reading with a
portable energy logger. Logger
data provides a rough order of
magnitude comparison of what is
being billed versus what is actu-
ally used. A significant deviation
between the amount charged for
electricity usage and the logger
data would signal the need to
investigate the sub meter setup.
4. Rebates and financial
incentives
Utility companies offer incentives
and rebates as a way to encour-
age their customers to decrease
energy use. The goal is to serve
more customers with the same
existing power supply, since
building new power generation
plants is prohibitive. Many
incentives and rebates are
available for retrofitting existing
buildings, such as energy effi-
cient lighting and high efficiency
motors, as well as replacing
motor starters with variable
frequency drives. In order to
receive the financial incentive,
the utility company will often
require verification of the energy
savings—an ideal scenario for a
load study. A pre-retrofit load
study will document the existing
energy use to provide baseline
data, while a post-retrofit load
study verifies the energy savings
achieved upon completion of the
modifications.
5. Troubleshooting
There are many times when the
only way to troubleshoot a prob-
lem is to capture and analyze
data over an extended period
of time. For these advanced
troubleshooting scenarios, energy
loggers are invaluable—and
they are much more afford-
able and easier to use than a
more complex power analyzer. A
good example is when a circuit
breaker trips randomly. Obvious
events, like a large motor start-
ing up, may not be the cause. In
fact, what causes the trips might
appear to be totally random or
may occur when technicians are
not around to observe it (like the
middle of the night). Because it’s
impractical for a maintenance
technician to monitor the load
until the circuit breaker trips,
connecting an energy logger
to the load side of the circuit
breaker to record the current
draw over time can help trouble-
shoot the trip.