Grid-Interactive Voltage Drop Wire Size Design Considerations
Ideally, for off-grid / grid-interactive
and on-grid inverter wiring, the total voltage drop for the grid-tied AC side should be <1% when possible. When we design complete systems, we do our best to stay under 1.5% (General industry acceptable
tolerance is 1 - 1.5% AC Vdrop). The max. of 1.5% AC voltage drop is all about maximizing inverter up time during Utility voltage swings.
Grid Tie Inverters Enphase, SMA, Sol-Ark and SolarEdge residential and light commercial applications.
Inverters / Chargers Off-Grid, stand alone, bimodal, battery based powering home, cabin, or Marine applications.
Inverters / chargers are solid-state electronic devices used in solar and wind energy system. The inverters Blue Pacific Solar sell employ the latest
in power electronics to produce AC power from a DC power source. The power source can be a battery bank, solar panels directly or the electricity
produced by a wind turbine. Inverters use a variety of different circuits and designs but we have narrowed those down to a few inverter
companies that manufacture durable, reliable inverters with he longest guarantees. Inverters use different switching devices and control methods
to affect the electrical waveform properties. As part of a complete solar or wind power system, inverters may also include functions for battery
charging, monitoring, system control and MPPT (maximum power point tracking).
Off-grid, or battery-based, inverters convert DC electricity from
a battery bank to AC. In this case, the solar array and/or wind generator is used to charge the batteries via a charge controller and only the power
demanded by the loads is inverted to AC. Because these systems do not have access to the electrical grid, it is important to properly size the
inverter and battery bank. The nameplate capacity of an inverter is measured by its maximum continuous output in watts. The inverter capacity limits the
sum of all AC loads you can operate simultaneously. Most AC appliances list their consumption on a tag located near the power cord and/or in the
equipment manufactures owner's manual. You will need to add up the consumption of all the appliances you may need to operate at once and that will
represent your minimum inverter size. If your appliances include induction motors, like washers, dryers, dishwashers, furnace electronic controls and
large power tools, be sure to select an inverter with surge capability to accommodate the higher start-up loads. You can start this process by listing
all the equipment you want to run and how long you need to run it each day on the average then send us your list. Blue Pacific Solar staff of Solar
Energy Consultants can guide you through the process of off-grid system design.
Off-grid inverters will output either pure sine wave or modified
sine wave AC electricity. Pure sine wave inverters can closely mimic utility grid power and will run virtually any AC appliance. Sine wave inverters
with cleaner waveforms, such as the Exeltech XP line, are often desired for sensitive audio or telecommunications equipment. Modified sine wave
inverters are an economical choice when waveform is not critical. They often have a high surge capacity for motor starting and generally retain
good efficiency when partially loaded. Unfortunately, this type of inverter may damage or fail to operate some sensitive appliances such as
rechargeable tools and flashlights, laser printers, copiers, variable speed drives. Some audio equipment will have a background buzz when operated or
some ceiling fans that are speed modulated with a speed control may have a problem with a modified sine wave inverter. Most battery-based inverters
found on our web site (portable inverters being the exception) supply standard 120VAC / 60Hz single-phase outputs. The SMA Sunny Island, Magnum MS-4024, and OutBack FX Series inverters can be
stacked in pairs for 240VAC. Pairs of OutBack and Sunny Island inverters can also be wired in parallel to provide more output power at 120VAC single-phase, or 120/240VAC split-phase. The Magnum MS-PAE inverters deliver 120 / 240VAC power from one
inverter, and can also be wired in parallel for greater power output.
Battery-based inverters may interfere with radio and television reception,
cause noise on telephones or buzz in audio equipment. Interference can be minimized by using pure sine wave inverters and by locating the inverter as
close to the batteries as practical, twisting together the cables that connect the inverter to the battery, running AC lines separate from other wiring
(such as telephone wires) and locating the inverter away from appliances that are susceptible to interference. All inverters cause interference with
AM radio reception. Battery-based inverters require high current from a battery bank to operate large loads. A 2kW inverter will draw nearly 200 A
from a 12 VDC battery bank. Large cables and good connections are required for safe operation.
Grid interactive, or
bimodal, inverters can export
power to the utility grid, but can also supply emergency backup power for critical loads during a grid outage. These inverters use a battery bank for
energy storage, and include an automatic transfer switch that enables them to safely operate off-grid during a blackout. Magnum Energy is a great
utility interactive inverter and we use the Magnum inverter on many of our home power emergency backup kits.
The grid interactive inverter is
connected to the battery bank (12, 24, or 48 VDC), then to an AC subpanel for critical loads, and the building's utility main panel. The battery bank
is charged by the solar array connected through a charge controller. Under normal conditions, it operates like any grid-tie inverter and will export
any excess power produced by the solar array. During a utility blackout, the inverter will automatically disconnect from the grid, and supply AC power to
the critical load subpanel by drawing energy from the battery bank. Blue Pacific Solar has a home emergency backup system that will operate with SMA or
Enphase MicroInverters using your solar array to recharge the batteries during blackouts if the system is under 3kW or 3,000 watts or about 12 235 watt
solar panels. When the outage is over, the inverter will automatically switch back to grid-tie operation and recharge the batteries. The Outback Radian
GS grid interactive inverters have split-phase 120/240 VAC output from a single inverter. The Outback GFX and SMA Sunny Island inverters have 120 VAC
output, but two inverters can be "stacked" for 120/240 VAC output. The SMA Sunny Island is designed to interact with a Sunny Boy grid-tie inverter to
create an "AC Coupled" power system.
