Electrical PV Equipment

ELECTRICAL PV EQUIPMENT

Design

Balance of System components are the components that make the PV system work. This training will help you become familiar with these components as they relate to designing a PV system.

1 | MODULES

WHAT TYPE OF MODULES DO WE USE?

Monocrystalline:

Each solar PV cell is made of a single silicon crystal.
Has the highest efficiency rating of the three main types of PV modules manufactured.

This information is often printed on spec sheets for modules. It is recommended, but not required, that you uptrain and learn to read spec sheets to improve your understanding of design.

Other types of modules not used by ION include:

Polycrystalline
Thin Film

STANDARD TEST CONDITIONS (STC)

STC is a test that tells us how modules perform under ideal conditions:

Tested under 1000 watts of sunlight
Tested at a temperature of 25 degrees Celsius (about 77 degrees Fahrenheit)

For example:

If a module is rated for 400W, this means that under the conditions above, the module can produce 400W of electricity.

The main takeaway here is that there are specific guidelines used to get these ratings and they are not always uniform from jurisdiction to jurisdiction regarding accepted methods for equipment rating. For example: some jurisdictions want us to include the PTC (PV USA Test Conditions) rating of modules instead. A different set of parameters is used to get the PTC rating. For most jurisdictions, STC will be used.

This is normally a matter handled by our compliance department but it is important for all of Design & Engineering to understand the different ratings and methods.

MODULE EFFICIENCY

Efficiency tells you how much sunlight the PV Module is capable of converting into usable electricity.

If your efficiency rating is 15%, that means 15% of the sunlight striking the module will be converted into usable electricity.

What can affect module efficiency?

Shading.
Cell reflective properties.
Temperature.
Environmental factors (orientation, inclination, latitude, climate, etc.)

2 | INVERTERS

BASIC INVERTER TYPES

Two basic types of inverters:

Microinverter:
- Each module has its own inverter. Modules are strung in parallel and run AC to a PV circuit combiner box where all solar circuits are consolidated.
- this is the type of inverter used here at ION

This type of inverter is not currently used by ION:

String Inverter:
- Modules are strung together in series and run DC to a single inverter which combines the strings and converts to AC power.

MICRO INVERTER

STRING INVERTER

DIFFERENCES IN WIRING AND EFFICIENCY

Microinverter:
- Micro inverters are strung parallel. This combines the Ampacity while the voltage remains the same
- Because the energy is conditioned and inverted at the source, the efficiency of each module will be independent from the other modules in the string.
String Inverter:
- Modules are strung together in series. This combines the voltage of each module while the ampacity will remain the same.
- Because the modules are strung in series with a combined output, the efficiency of the entire string of modules is limited by the least efficient module
  - The way around this is to utilize DC Optimizers which condition the current output of each module to get around this hiccup.

Since ION uses microinverters, our designers never have to worry about choosing the correct inverter size or using DC optimizers. Using micro inverters makes your job as a designer a little simpler in most cases. It is still important to be familiar with the difference as many aspects of PV design are controlled by availability of equipment and it is not impossible that we could switch to designing with string inverters some day.

3 | BOS

WHAT IS BOS?

Balance-of-System (BOS) components include all of the equipment involved in PV system installation and function other than the modules themselves.

Typically, BOS can make up about 50% of the installation cost.

JUNCTION BOXES

A junction box is an enclosure where conductors can be safely spliced together and maintained.

When do we use junction boxes?

When splicing roof PV cable to Romex for attic run to the combiner box
Called a roof junction box

When else do we use junction boxes?

When connecting attic Romex to general use THHN for PV circuitry.

COMBINER BOXES

A combiner panel is a BOS component used to consolidate PV circuits for the purpose of solar interconnection.

The purpose of this is to create one single output for the purpose of tying into the existing electrical system
This is also where the PV production monitoring hardware is also housed.

Combiner Envoy:

Enphase IQ Combiners come pre-installed with an IQ Gateway (Envoy)
Envoy allows for system monitoring in real time.

The default connection will be Wi-Fi. When the customer does not have Wi-Fi, then the Envoy will need to be commissioned using an alternative method.

Typically, a cell modem will be installed to facilitate the connection in this case.

PV METER SOCKETS

PV meters are used to track PV production for Net Metering purposes.

Some utilities install bi-directional meters for net metering purposes and no PV meter socket would be installed in this case.

Other utilities will require a second production meter to be installed specifically to track PV production.

Notice that the PV meter (left) looks very similar to the utility meter (right)

AC DISCONNECTS

Two types of general AC disconnects you will see:

Fusible AC disconnect
Non-fusible AC disconnect

AC disconnects are installed under the following circumstances:

Utility required for rapid shutdown and equipment isolation purposes. (non-fused)

Tap type interconnections require a fusible disconnect.
- This includes both supply side and load side taps.

RACEWAYS

A raceway is an enclosed conduit that forms a physical pathway for electrical wiring.

Common types of raceways:

Electrical Metallic Tubing (EMT)
Non-Metallic Conduit (PVC)
Flexible Metal Conduit (FMC)
Galvanized Rigid Steel Conduit (GRC, RMC)

EMT

EMT (Electrical Metallic Tubing) is a type of conduit used to protect and direct general outdoor circuitry.

This is the type of conduit used to as a raceway between all "wall equipment," or BOS components that would be mounted on the exterior of the home next to the existing electrical equipment.

PVC

PVC is a type of conduit also generally used outdoors. It is common for this type of tubing to be used for service risers.

PVC is also typically used here at ION as an underground conduit under high stress areas such as driveways and roads when underground runs are required.

FMC

FMC is a flexible type of conduit that is approved for indoor use. It can sometimes come pre-filled with conductors, known as MC.

This type of conduit should mainly be seen indoors
It should never be seen outdoors without a PVC jacket for weatherproofing.

RMC

RMC has similar applications to PVC. It is generally seen used as a service riser.

This type of conduit may also be used underground at shallower depths.

WIRES & CABLES

SE-R and SE-U
NM-B/Romex
THHN
MC
UF-B
URD
Overhead Service Cable

SE-R & SE-U

These are the pre-assembled cables commonly used to supply a panel with energy from the meter to the MSP or the MSP to a sub panel.

SE-U:

SEU is an unarmored Style U flat service electrical cable with two-phase conductors and a concentric neutral (middle example of the photo at the top).
Generally used for service conductors between the meter and MSP

SE-R:

SER is a round service electrical cable that typically has up to four conductors and a bare ground (right most example of the photo at the top).
Generally used to feed sub panel from the MSP.

NM-B (ROMEX)

NM-B is commonly called "Romex" which is the name of the most popular manufacturer of NM-B type cable. NM-B is a type of preassembled flat-wound cable generally used residential circuitry such as outlets and lighting. It is for interior use and is ran free-air through walls and attic spaces.

These cables are generally pre-configured with 3-4 conductors: 1 or 2 ungrounded conductor, 1 grounded conductor, and 1 equipment grounding conductor.
This cable is used for interior attic runs for PV circuitry here at ION.

THHN

THHN stands for "Thermoplastic High Heat-resistant Nylon-coated wire." This type of wire is used for general wiring purposes. THHN comes in a variety of sizes to handle different ampacity currents.

THHN is generally used for localized circuitry, in other words, you wouldn't use THHN to do an extended wire run.
It is very common for PV circuitry to utilize NM-B for the wire run through the attic only to later splice to THHN later in the schedule for the purpose of wiring Combiner panels, PV meters, and AC disconnects.

MC

MC is simply FMC that is pre-filled with THHN. This type of cable is used for interior wire runs similarly to Romex.

These cables are generally pre-configured with 3-4 conductors: 1 or 2 ungrounded conductor, 1 grounded conductor, and 1 equipment grounding conductor.
This cable can also some times be used for attic wire runs for PV circuitry.

UF-B

UF-B is a preassembled cable type used for underground use. Typically, they are used to feed an outbuilding or otherwise distribute power to an accessory structure from the main home.

These cables are generally pre-configured with 3-4 conductors: 1 or 2 ungrounded conductor, 1 grounded conductor, and 1 equipment grounding conductor.
These cables are for underground use only either in conduit or direct burial.

URD

URD is and underground cable type used in similar applications as SE-R/SE-U. The key difference being the underground rating.

URD is used to supply services on accessory structures away from the main home.
URD may also be used for extended underground runs where is may be necessary to upsize wire.
Typically comes pre-assembled as either triplex or quadruplex cable.

OVERHEAD SERVICE CABLE

Overhead Service Cable is similar to URD but is used for overhead spans rather than underground. It is very common for utility distribution to use this type of cable to distribute power to a customer's home when the service orientation is overhead.

This type of cable can also be used here at ION for extended spans to service accessory structures.

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Design & Engineering > Design 3 - Electrical PV Equipment

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