Application Note

3 Fluke Corporation Troubleshooting photovoltaic systems: three typical problems
When you get up on the roof,
visually check the entire system
for any obvious damage. Also,
keep in mind that someone may
have disconnected the wiring
accidentally while servicing
another device on the roof. Once
the module or array that is not
producing power is found, check
all wiring, switches, fuses, and
circuit breakers. Replace blown
fuses and reset the breakers
and switches. Keep in mind
that since the PV system is on
the roof that a lighting strike or
power surge may have affected
it. With the large amount of
wiring present, check for broken
wires and loose or dirty con-
nections. Replace and clean as
needed. Especially be on the
lookout for wire nuts that are
connecting modules together.
They may have worked loose
and caused lack of contact.
The concentrators can be a
great place to troubleshoot the
system because the individual
wires from the modules are
brought back there. Each module
may have a fuse which should
be checked with the 381 meter.
Wiring problems and loose
connections may also cause a
particular module to produce too
low a voltage. Again, all wiring
connections should be checked.
If a particular module output
is low, it may mean that an
individual section of cells is bad.
These may be traced out using
the 381 meter at the junction
boxes until the culprit is found.
Any dirt on the modules, or
modules in the shade, can cause
a reduced output. Although the
modules are usually designed to
be maintenance free for years,
they may need to be cleaned.
Pollen can be a problem in some
areas of the country. Check the
system with the 381 meter after
any corrections are made.
Troubleshooting Problem #2:
Load Problem
Remember that the PV system is
used to operate building electri-
cal loads. Any problems with the
loads will affect the system as
well. The first step is to check
the load switches, fuses, and
breakers. With the 381’s voltme-
ter, check to see that the proper
voltage is present at the load’s
connection. Next use the 381
to check the fuses and circuit
breakers. If there are blown
fuses or tripped breakers, locate
the cause and fix or replace the
faulty component. If the load
is a motor, an internal thermal
breaker might be tripped or
there might be an open winding
in the motor. For testing pur-
poses plug in another load and
see if it operates properly.
As with any electrical system,
check for broken wires and any
loose connections. Clean all
dirty connections and replace all
bad wiring. With the power off,
check for and repair any ground
faults. If any fuses and break-
ers blow or trip again, there is
a problem short that must be
located and repaired.
If the load still does not oper-
ate properly, use the 381 meter
to check the system’s voltage at
the load’s connection. The wire
size may be too small and need
to be increased. It may also be
possible that that the wire runs
to the load are too long. This
will show up as a low voltage
at the load. In this case you can
reduce the load on the circuit or
run a larger wire.
Troubleshooting Problem #3:
Inverter Problem
Many HVAC technicians work
with variable speed drives every
day, so we are used to checking
ac and dc power. The inverter
in a PV system can also fail and
cause problems. The inverter
converts dc from the PV system
into ac power for building use. If
the inverter is not producing the
correct output first use the 381’s
voltmeter and dc ammeter to
check and record the inverter’s
operating dc input voltage and
current level. On the ac side, use
the 381 clamp meter to check
the inverter’s output voltage
and current levels. As men-
tioned previously, many of these
systems have a display that
To measure the current output of this photovoltaic cell, a technician wraps the 381iFlex™
flexible current probe around the conductor.