Grid-tied PV systems without battery backup or emergency or critical power
panels generally use the manufacturer’s setting with the inverter. Study the litera-
ture and installation manual to ensure that the settings are right for your system.
There are occasions where settings need adjusting. One example of this is if a
positive grounded system is installed. Some settings can be confirmed through
monitoring, and some can be tested by a multimeter.
Grid-tied PV systems with battery backup need very specific programming.
Follow all equipment instruction manual procedures. However, know how you
are going to use the system. Develop a system operation plan with your desired
settings. Some mechanisms are very complex to program. PV system performance
and safety rely on understanding and knowing the importance of each program-
setting mode. Double- or triple-check the settings before operations begin. Check
again after operations begin as well.
Test the entire system once the inverter is programmed. Go through each cir-
cuit. Test all operating modes for every part of the PV system for appropriate
functionality.
During these processes and procedures, we highly recommend double and
triple checking the whole PV system—settings, voltages, currents, and polarity.
One of the greatest lessons learned in the PV industry is to get it right the first
time. These items must be accurate. Unnecessary service calls will occur if you
rush a set of tests, are overconfident in your own capabilities, are sloppy or tired,
want to wrap up the day, or make inappropriate assumptions.
These service calls usually cost the company about $200 to $300 or more per
visit. This is very expensive compared to spending 10 or 15 minutes on a PV
system to get it right. Not completing the job properly causes a customer and
management loss of confidence, especially when the installer or technician says,
“It was only a loose wire or the wrong setting.”
Performance Inspection and Monitoring
System performance monitoring for all PV systems is crucial. It extends longevity
and increases production. After installation, perform a thorough system checkout.
However, before we proceed we will review some of the issues and applica-
tions of using jumpers.
References to the use of bonding jumpers are found throughout the 2011
Code. Its applications must be put into perspective by first reviewing the defini-
tions of jumpers. In Article 100, Definitions, NEC 2011 defines jumpers thus:
“Bonding Conductor or Jumper. A reliable conductor to ensure the required
electrical conductivity between metal parts required to be electrically
connected.”
“Bonding Jumper, Equipment. The connection between two or more
portions of the equipment grounding conductor.”
CHAPTER 10 Quality Control, Testing, Troubleshooting, Monitoring 235
“Bonding Jumper, Main. The connection between the grounded circuit
conductor and the equipment grounding conductor at the service.”
“Bonding Jumper, System. The connection between the grounded circuit
conductor and the supply-side bonding jumper, or the equipment
grounding conductor, or both, at a separately derived system.”
It is important to understand what is a recognized and acceptable method of
using jumpers, which may be found in:
CODE: 250.8 CONNECTION OF GROUNDING AND BONDING EQUIPMENT
(A) Permitted Methods. Equipment grounding conductors, grounding electrode conductors,
and bonding jumpers shall be connected by one of the following means:
(1) Listed pressure connectors
(2) Terminal bars
(3) Pressure connectors listed as grounding and bonding equipment
(4) Exothermic welding process
(5) Machine screw-type fasteners that engage not less than two threads or are secured with a nut
(6) Thread-forming machine screws that engage not less than two threads in the enclosure
(7) Connections that are part of a listed assembly
(8) Other listed means:
The uses of jumpers in PV applications include yet may not be limited to the following. A thor-
ough understanding of the use and reasons for using jumpers requires additional study and
instruction.
1. Continuity of Equipment and System Grounding:
In the 2005 NEC, sections NEC 690.48 and 690.49 included new provisions that require that
jumpers be installed as follows:
“690.48 Continuity of Equipment Grounding Systems. Where the removal of equipment discon-
nects the bonding connection between the grounding electrode conductor and exposed con-
ducting surfaces in the photovoltaic source or output circuit equipment, a bonding jumper shall
be installed while the equipment is removed.”
And “690.49 Continuity of Photovoltaic Source and Output Circuit Grounded Conduc-
tors. Where the removal of the utility-interactive inverter or other equipment disconnects the
bonding connection between the grounding electrode conductor and the photovoltaic source
and/or photovoltaic output circuit grounded conductor, a bonding jumper shall be installed to
maintain the system grounding while the inverter or other equipment is removed.”
These provisions are included to protect maintenance technicians and others from inadver-
tently ungrounding equipment when inverters are removed during maintenance services. As a
result, an ungrounded system will not create a hazard for future worker or owners who may be
unaware that the system is ungrounded.
236 ADVANCED PHOTOVOLTAIC INSTALLATIONS
A system checkout includes the following steps to monitor performance:
Visually inspect the entire PV system to ensure that all components,
terminations, and connections are secure.
Ensure that all wiring is properly connected and neatly bundled.
Apply weather sealing adequately but not excessively.
Check the grounding system so that all required parts are
properly grounded.
Turn off all disconnects and breakers.
Leave fuses out of the holders.
CODE: 250.8 CONNECTION OF GROUNDING AND BONDING EQUIPMENT
(CONTINUED)
2. With Regards to Optional Standby System Panels: When an optional standby system
panel is a single-phase 3-wire panel which is wired with a jumper between phases to provide a
connection for an inverter with 120Vac output to both busbars of the panel, it must be labeled
per NEC 690.10(C). The panel label must read: “WARNING, SINGLE 120-VOLT SUPPLY. DO NOT
CONNECT MULTIWIRE BRANCH CIRCUITS!”
3. When Performing a System Checkout Testing and pre-commissioning Inspection:
Remember that you will not be testing at STC and therefore you must consider the testing in
that light. Please review the definition of standard test conditions and compare them to the
conditions that exist as you do your testing.
With consistent irradiance during the test, short-circuit currents should be within 5 percent.
Again, visually confirm that all breakers and switches are open and check to see that all fuse
holders are empty. Do not rely on memory or on others unless you have a strict protocol for
communications of these details.
Measure the voltage across the circuit where you are going to install the shorting jumper.
That voltage must be zero!
If it is not zero, you must not proceed until you have determined why it is not zero. Do not
install the shorting jumper until the issue is resolved. If the voltage is zero, it is safe to install a
shorting jumper.
4. Removing A Panel From An Array:
The PV system array is usually an integral part of the grounding system. By removing a panel
you have now removed continuity. During maintenance on an array, the continuity of grounding
must be maintained, and jumpers may be required. Grounding and bonding connections must
always be inspected during routine maintenance. This becomes especially critical for their integ-
rity, security and corrosion impacts where corrective actions may be required.
(Excerpts from NEC 2011 reprinted with permission from NFPA 70®, National Electrical Code®, Copyright© 2010, National
Fire Protection Association, Quincy, MA.)
CHAPTER 10 Quality Control, Testing, Troubleshooting, Monitoring 237
Examine the polarity, voltage, and current of all source circuits and battery
strings, if applicable.
Combiner strings need to be tested quickly, and all under the same
conditions. You are looking for a relationship between strings to see
how balanced the system will be. Balance equals energy production.
You will use the data later to see if the strings compare at the same
ration of variation, which should be very small.
It is best to check batteries at full charge and after they have set and
stabilized their temperature.
Check open-circuit voltages to make sure they are within
1 to 2 percent of each other.
Short-circuit currents should be within 2 to 5 percent of
each other if the irradiance stays consistent during the test.
Install a shorting jumper if the circuit voltage is zero.
Insert a source-circuit fuse in the first source-circuit fuse
holder, close the disconnect, calculate the short-circuit
current, and open the disconnect.
Repeat the procedure for each source-circuit fuse holder.
Remove the shorting jumper, and install the source-
circuit fuses.
Confirm that there is only one grounding point.
Document, document, document!
This is true of your test data. This is also true for any special
design or other issues on the system. Keep data documentation
for instances when service technicians have to come out to the
site in the future for any reason. They will need this information for review. After
these initial checks, look into performance monitoring for your specific PV system.
Performance monitoring for standalone PV systems with charge controllers
includes the following steps:
1. From your system plan, complete the required settings.
2. Close the battery disconnect to connect the batteries to the charge controller
input after all polarity is assured.
3. Apply power to the charge controller by closing the PV output-circuit
disconnect.
4. Adjust the charge controller using the instruction manual, as needed.
5. Turn on the loads with all charge controller adjustments, which have
been made.
6. Adjust the charge controller to control the voltage and current to the loads
and check for system batteries and loads.
7. Start the PV system operation once the charge controllers have been
adjusted and confirmed.
TECH TIPS
The closer the voltage and
current values are to each other,
the better and more balanced the
strings are. This results in high energy
production.
TECH TIPS
Measure the voltage across the
circuit where the shorting jumper is
to be installed. It must be zero. If it is
not zero, then stop. Do not install the
shorting jumper.
238 ADVANCED PHOTOVOLTAIC INSTALLATIONS
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