Solar Panel Connections and Maintenance

Trunk Bus and Parallel Connections

• Trunk bus is a wiring harness supported by a torque tube.

• A mini trunk bus can be used for parallel connections in a shop setting.

Series and Parallel Panel Connections

• Panels are connected in series first (positive to negative, positive to negative, etc.).

• After the series connection, the string of panels is connected in parallel using trunk buses.

• The positive end of the series string connects to a positive trunk bus, and the negative end connects to a negative trunk bus.

• Another series-connected string is then connected between the same positive and negative trunk buses, creating a parallel connection.

Harness and Couplers

• Blue harness indicates the negative conductor.

• Positive harness will have a negative coupler to ensure opposite genders on each end for coupling.

• This setup is used to connect multimeters for testing.

Measuring with Couplers

• For a series-connected string of five panels, connections are made negative to positive.

• To measure between the ends, a long lead harness with a positive coupler on one end and a negative coupler on the other is used.

• This allows measuring between the positive and negative ends of the series string.

Polarity and Gendered Couplers

• Couplers are labeled positive and negative, but this is just for guidance.

• The positive coupler can be put on the negative lead as long as the opposite gender lead is used for connection.

• A positive trunk bus will have multiple couplers to plug into the solar panel's opposite-gendered couplers.

• A negative gendered harness will plug into the unused conductors/couplers on the panels.

Junction Boxes

• Solar panels have junction boxes labeled positive and negative.

• Negative color should be on the opposite end to ensure proper connections.

• Having opposite polarities is essential for connecting components.

Importance of Drawings

• Without drawings, technicians often face connection issues with same-gendered couplers.

• One end has five like couplers, while the opposite gendered end connects to the meter.

• Like couplers connect to the positive or negative of the panels for parallel connection.

MC4 Connectors and Ingress Protection

• MC4 connectors, T4, and H4 are types of solar electrical connectors.

• Connectors enable disconnecting and reconnecting for testing and replacements.

• These connectors are water and dust resistant with a compression-style sleeve and o-ring seal.

• IP (Ingress Protection) rating indicates protection against dust and moisture.

• Connectors are IP65 when unmated and IP68 when mated.

Connector Types and Safety

• MC4 is the most common term, a trademark by Staubli (a European brand).

• Warning: Do not disconnect under load to prevent arcing due to high DC voltage.

• Disconnecting under load can cause arcing and is dangerous.

Male and Female Couplers

• The electrical conductor determines the gender, not the coupler housing.

• Male coupler houses a male pin, while female coupler houses a female pin.

• The plastic housing is typically the opposite polarity of the conductor.

Installation and Fail-Safes

• It's possible to insert the wrong conductor into a coupler, but it will lock in place.

• If inserted incorrectly, the conductor cannot be removed and must be cut.

• The opposite conductor will not fit in the wrong coupler, providing a fail-safe.

• Since they are inexpensive, it's better to replace than attempt to remove.

Tooling and Testing

• Specialized tools are required for creating connections, including cutters, strippers, and crimpers.

• Connections are tested to ensure low resistance.

Wire Strippers

• Specialized wire strippers grab and hold the wire while stripping the insulation.

• The appropriate gauge setting must be used to strip the insulation properly.

Crimpers

• Ratcheting crimpers with interchangeable jaws are used for making connections.

• A release lever is available to undo the crimp if needed.

Wire Ferrules

• Wire ferrules are important for stranded wires to prevent loosening over time.

• The tool crimps a metal cylinder around the stranded wires, effectively making it a solid wire.

• This ensures a secure connection in screw terminals.

Provided Tooling and PPE

• All necessary tooling and PPE are provided; technicians should not have to spend money on work-related items.

Spanner Wrenches and Disconnect Tools

• Spanner wrenches and disconnect tools are used to disconnect couplers, especially when wearing hot gloves.

• These tools help pinch the barbs and pull the connectors apart.

• Multi-tools have a spanner on one side to tighten or loosen couplers.

Torque Wrenches

• Torque wrenches should be used to ensure proper compression sleeve tightness.

• A photovoltaic kit from Vera includes an adjustable torque wrench.

• 3 < x < 6 (newton meters) is the adjustable range.

Compression Sleeve Torque

• The compression sleeve has a tapered fit.

• Tighter compression sleeves provide more bite into the insulation.

• The correct compression sleeve gap is essential to avoid over or under torquing.

• Manufacturer specifications often include charts with conductor size and insulation types for proper torque.

Myths About Slipping Wrenches

• A common myth is that spanner wrenches are designed to slip at a predetermined torque.

• These wrenches are not calibrated and can wear out, leading to inaccurate torque.

• Nexera procedures require torque to 3.5 newton meters using a specific coupler.

• Different couplers have different specified torque values based on conductor size.

Werra Torque Wrench Kit

• It can potentially prevent MC4 connector failures.

• The Werra voltaic torque wrench kit number should be provided for easy ordering.

Key Considerations for Connections

• Use the appropriate 12-gauge center position on the crimper jaws for 12-gauge wire.

• Using the wrong gauge can lead to over or under crimping.

• The crimper has an m-shape on the top jaw to bend over the ears of the pin and socket.

Inspection Stages

• Strip the appropriate amount of insulation (approximately 1/4 to 3/8 inch).

• Inspect for the correct strip length and crimp the crimp area fully.

• Perform a tug test to ensure the connection is secure.

• Insert the pin and socket into the opposite gendered coupler, and tug test again.

Common Mistakes and Failures

• Improper installation, dirt, grease, or damaged parts can cause failures.

• Unseated parts can lead to issues.

• Boxes of couplers falling into the sand can contaminate the parts.

• Worn tools and uncalibrated torque wrenches can lead to poor connections.

Calibration and Mismatched Connectors

• Calibration is crucial for all tooling that performs repetitive tasks.

• Torque wrenches should be calibrated and certified annually.

• Mismatched connectors can cause electrical issues.

• Replace in pairs (positive and negative) to ensure consistent tolerances and electrical conductivity.

Counterfeit Products

• Counterfeit or untested products can cause issues.

• Familiarize yourself with different styles of connectors as they may have different torque values.

Spotting Problems

• Loose or over-tightened compression sleeves can indicate issues.

• Check for threads showing or bottomed-out compression sleeves.

• Unseated parts can cause arcing.

• Cable management should prevent cables from rubbing and wearing out.

• Damaged or overheated connections can be identified by discoloration or melting.