Solar Power Solutions

Eaton Solar PV Balance of System Products

TYPICAL COMPONENTS FOR 10kW microFIT
Solar Photovoltaic Installation

Eaton is a market leader in the manufacture of AC and DC electrical power distribution equipment and industrial control and automation products. Eaton has a large manufacturing presence in Ontario and utilizes existing Ontario based facilities in Perth, Mississauga, Oshawa and Milton to assemble and supply Balance of System (BOS) electrical components and assemblies for solar PV installations from the smallest microFIT project through larger rooftop installations and multi-megawatt solar farms under the Ontario Power Authority's Feed-In Tariff (FIT) program.

As a home owner, farmer or small business owner in Ontario, you have the opportunity to develop a solar PV project of 10kW or less in size on your property. You will be paid a guaranteed rate for 20 years for all the electricity you produce through the microFIT program. Currently (2010) that rate is up to 80.2¢ / kWh. All installations are Grid Tied solar electric systems that are capable of feeding power to the grid (or utility company). This is in contrast to "off-grid" or "stand alone" systems that do not have this capability.

The diagram below represents a typical grid tied 10kW Solar PV installation and indicates all of the components that are normally required.

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Solar Panels
A photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. The photovoltaic module (solar panel) is then used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications.

• PV String: A set of 'Solar Panels' connected in series is known as a PV String.


• PV Array: A PV Array is made up of a group of PV Strings. A single photovoltaic module can only produce a limited amount of power so many installations contain several strings of modules or panels and this is known as a photovoltaic array.

String Combiner: String Combiners, often referred to as source combiners, are located closest to the "strings" of solar panels. They are used in solar installations to combine the inputs from multiple strings of solar panels into one output circuit.

DC Disconnect Switch: A DC Disconnect Switch is required ahead of the inverter to isolate the load from the PV source. The DC switch is often shipped as part of the inverter but may also be sourced separately.

Inverter: An inverter is an electrical device that converts direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits. The DC input voltage in microFIT Grid-tie installations is normally <600vdc. The AC Output from the inverter is normally 120/240V single phase.

AC Panel (Loadcentre): When multiple inverters are used, there is a need to recombine the AC output into a single feed that can be commented to the utility meter through an AC Disconnect.

Utility Source Disconnect: The Electrical Safety Authority requires that a Service Entrance Disconnect be provided next to the utility meter.

Meter Socket: A utility grade meter socket is required to accurately measure the Solar PV power that is produced. Some Local Distribution Companies have standardized on 200A Meter Sockets. For others, 100A sockets are acceptable. Refer to your local LDC for specific requirements.

Some microFIT installations may only utilize a single inverter in which case, the AC Loadcentre may not be required. Also, the 2 circuit string combiner box referenced above may need to be expanded to accommodate 3 or 4 string inputs. Similarly, some applications may use up to 3 inverters in which case a total of (3) 2 circuit string combiner boxes would be required.


OPA Recommended Connection Types for microFIT installations

There are three different connection configurations for microFIT Grid Tied installations; indirectly connected in series, indirectly connected in parallel and directly connected. The OPA issued a recommendation recently that installers not use a series connection. This was based on information from Measurement Canada that it will not recognize or support" the in-series metering configuration defined by Figure 2(b) of the microFIT Rules. This is primarily because there could be an unacceptable level of error that results when two meters are used to measure electricity consumed by a load customer.

Series Connection: (Not Recommended). The solar meter is connected into a load breaker in an existing panel. This method is also known as a "Behind the meter" connection since it is on the load side of the Utility Meter.

Parallel Connection: A Parallel connection is made in front of the utility meter. This type of connection utilizes a Dual Meter Socket that includes 2 sockets tied together on a common bus. The Incoming Utility Power is connected to the common line side bus form the 2 meter sockets. The Solar AC Disconnect Switch is connected to the load side of the Solar Meter. The load side of the utility meter feeds into the home service.

Direct Connection: A direct connection requires a single meter socket that is connected directly to the utility grid and does not interconnect with the existing building services. This connection is normally made if the project is located at a significant distance from the existing load customer (e.g., the house) and is closer to the main distribution system.


Solar PV Balance of System Components
Available from Eaton