Use UL-listed charge controllers. These charge controllers are less likely to
have safety issues.
Use multipole switches or circuit breakers to disengage the battery from the
charge controller.
Ungrounded Systems
Ungrounded PV systems should have other mechanisms in place. Specifically,
ungrounded systems should have overcurrent devices and disconnects. The over-
current devices and disconnects should be placed on every ungrounded con-
ductor. [690.13]
Multiple Power Sources
Sometimes PV systems have multiple power sources. These power sources include:
PV output
Battery system
Generators
Other backup power sources (such as wind or hydroelectric power)
PV systems with several interconnected energy sources should have separate
switching. Each disconnect switch should be labeled. Inspectors and workers need
to know if the PV system is a hybrid system with wind, water, or gas as its backup
power source.
Illustrations of the interconnection are not required. However, they may be
advantageous. Place the drawing near the PV system disconnects.
Per NEC Article 230.71, place all disconnects near one another to ease
management of all the disconnect switches that are needed to shut the power off
from the entire PV system.
CHAPTER 8 Connecting the Sun to the Home and the Utility 201
Chapter 8 assessment
Connecting the Sun to the Home and the Utility
1. PV arrays are live when mounted and installed.
A. True
B. False
2. What is the voltage for a PV module that has a 17.1V STC rating with module temperature
of 60 degrees Celsius and 1,000 W/m
2
radiation?
A. 20.1V
B. 17.1V
C. 14.1V
D. 12.0V
3. Why would wires with oversized ampacity work in battery interconnections?
A. Equalize all battery current and voltage flow
B. Give battery short-circuit current a path
C. Offer load or array size increases
D. Secure batteries
4. Using a 2,500 W inverter to supply a 120 V AC load of 1,500 W, what is the inverter output
ampacity?
A. 12.5A
B. 15.6A
C. 20.8A
D. 26.0A
Chapter 8 summary
Installing PV systems requires knowledge of the system as a whole. It requires understanding
all of the components. You must learn how they work together. The interconnections within a
PV system are crucial to its functionality and performance.
Interconnections between the PV system and the building or dwelling are imperative to
PV installation. Important interconnections between the PV system and the power company
determine what components are needed.
Know the guidelines for various wiring types. This knowledge helps identify the best con-
ductors to use under particular conditions. It makes installation easier. Grounding the PV
system and all of its components curtails the possibility of damage. Fault protection and over-
current protection procedures keep PV systems and PV system components safe.
Key ConCepts and terms
Amperes interrupting rating (AIR)
Blocking diode
Grounding electrode conductor (GEC)
Ungrounded conductor
202
ADVANCED PHOTOVOLTAIC INSTALLATIONS
5. What is the smallest size equipment-grounding conductor (type THWN-2) for
the PV output circuit?
A. 14 AWG copper
B. 12 AWG copper
C. 10 AWG copper
D. 8 AWG copper
6. What color is the equipment-grounding conductor?
A. White
B. Black
C. Red
D. Green
7. All unlisted PV equipment must be grounded properly because the PV system
has to be grounded, even if the negative input terminal on the inverter is the
point of system ground.
A. True
B. False
8. What are some of the disconnect switches in large PV systems?
A. String disconnect switches
B. Disconnects for sub-arrays
C. PV disconnects for every inverter
D. AC output disconnects for every inverter
E. All of the above
9. Fuses and circuit breakers can be used as overcurrent devices.
A. True
B. False
10. Where should overcurrent devices and disconnects be located?
A. Listed panel boards
B. Unlisted enclosures
C. Outside in the elements
D. Bathrooms or laundry rooms
CHAPTER 8 Connecting the Sun to the Home and the Utility 203
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