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Utility-Interactive Microinverter
The rapidly advancing technology making this new product
possible is the utility-interactive microinverter. These
devices are governed by
IEEE1547 — Standard for
Interconnecting Distributed Resources with Electric Power
Systems
. This is a standard of the
Institute of Electrical and
Electronics Engineers
meant to provide a set of criteria and
requirements for the interconnection of distributed
generation resources into the power grid in the United
States.
UL1741 - Standard for Safety Inverters, Converters,
Controllers and Interconnection System Equipment for Use
with Distributed Energy Resources --
addresses
requirements for microinverters, converters, charge
controllers and interconnection system equipment (ISE)
intended for use in stand-alone (not grid-connected) or
utility-interactive (grid-connected) power systems.
Utility-interactive microinverters, converters and ISE are
intended to be operated in parallel with an electric power
system (EPS) to supply power to common loads.
IMPORTANT
The customer needs to understand that this is a
utility-interactive photovoltaic (PV) system which WILL
NOT generate power when the grid power is down (OFF).
Due to the differences in power quality between the grid
and generators, the PV module system will not produce
power concurrently with a back-up generator.
ELECTRIC UTILITIES AND SOLAR PV UTILITY
INTERACTIVE SYSTEMS
Does the electric utility have any special
requirements?
The local utility will want to be aware of the presence of
such a system on the grid. Usually, there will be an
interconnection application that needs to be submitted to
the local utility. Some utilities will have a particular type of
electrical disconnect (indicating, lockable disconnect
switch) which they want to be used in an interactive
system.
Is there an incentive program?
If there is a rebate involved, the utility may require that a
separate meter, which is usually referred to as a
Renewable Energy Credit {REC} meter, be installed in a
location where it measures the power generated by the
solar PV system.
Is there a minimum kilowatt (KW) threshold?
Some utilities require a 1KW or 2KW threshold for this
rebate/incentive programs.
Does the electric utility have a net-metering program?
The larger and publicly owned utilities tend to have
net-metering programs. Net-metering rules specify how
credit for
net generation of energy
is returned to the
homeowner. The total is the amount of electricity
consumed, less the amount of electricity produced.
NOTE — Additional liability insurance may be required when
a utility-interactive system is installed in a home.
SunSource
®-
Ready Heat Pumps and Air
Conditioners
The outdoor portion of the SunSource
®
HVAC system has a
standard power connection to the dedicated HVAC branch
circuit. It also has a second 240-volt AC power source
connection for the utility-interactive solar power input. Solar
photovoltaic (PV) alternating current modules (incorporating
grid tie microinverters) are the source of the solar power.
Figure 2. SunSource
®
Solar Sub-Panel
The heat pumps and air conditioners have been Electrical
Testing Laboratories (ETL) listed to accept the Lennox
®
Solar Sub-Panel (an ETL-listed accessory). Units not
designated as solar-ready are NOT safety agency approved
for solar applications.