Solar Panel Maintenance and Troubleshooting

Door Safety and Combiner Inspection

• Door Positioning: When approaching electrical cabinets, stand on the hinge side of the door. This minimizes exposure to potential heat or arcs.
• Avoiding Blind Door Openings: Do not open doors blindly. Observe what's happening inside before fully opening.
• Using Back Pressure: If a door feels stuck, apply back pressure to peel the gasket.
• Initial Inspection: Upon opening a combiner, quickly scan for any immediate hazards.

Voltage Measurement and Safety

• Voltmeter Usage: Use a DC voltmeter to check voltage levels.
• DC Voltmeter Setting: The DC setting on a voltmeter is indicated by two straight lines.
• Polarity Insensitivity (Initial Check): When initially checking for voltage presence, polarity is not critical. The absolute value is the primary concern.
• Loaded Voltage: A loaded voltage should be observed. 104 volts is not a good voltage in this context.
• Pole Identification: In DC circuits, use the term "poles" instead of "phases".
• Positive Pole Identification: Positive inputs often connect to a fuse block.

Grounding and Polarity Conventions

• DC Polarity Color Coding: In DC systems, the darker color (typically black) represents the negative or common.
• Ground Wire Identification: Ground wires are typically green or bare copper and connect directly to the earth.
• Ground Connection: A bare copper wire is connected directly to the earth, often via a sleeve buried in the ground.
• Voltage Confirmation: A reading of 656 volts is considered satisfactory for this system.
• Lead Placement: When measuring voltage to ground, connect the common (negative) lead to the ground.
• Polarity Check: A negative reading on the voltmeter indicates reversed leads.

DC Circuit Breaking and Safety Features

• Multiple Disconnects: DC circuits often have multiple disconnects (e.g., four switches) on the positive side to ensure arc extinction.
• AC vs DC Breaking: AC circuits typically only require breaking the circuit once, while DC requires multiple breaks due to its robust current flow.
• Polarity Convention Exception: In some systems, white wires may be negative if black is present, or black wires may be negative if red is present. This is noted as an inconsistent industry standard.
• Common Block: Negative wires are often bolted together in a common block.

Transient Voltage Surge Suppressor (TVSS)

• TVSS Function: A TVSS protects against transient voltages, such as those caused by lightning.
• Transient Voltage Definition: Transient voltage refers to a voltage that is not normally present in the system.
• Lightning Protection: Lightning strikes can induce voltage surges through the "corona effect."
• Corona Effect: When lightning strikes, the electrical wave propagates outwards and can induce voltage in nearby conductors.
• TVSS as a Sacrificial Component: A TVSS is a sacrificial device that diverts transient voltages to ground.
• Limitations of TVSS: A TVSS is not a failsafe against lightning and may not prevent damage from direct strikes.
• Protection Direction: A TVSS primarily protects the system from surges coming from the earth, not necessarily from direct strikes to the modules.

Fuse Block Inspection and Safety

• Ammeter Usage: Before tilting out any fuses, check for current using an ammeter.
• Checking for Circulating Current: Even with the switch off, circulating currents may exist.
• Safe Current Threshold: If the ammeter reads less than 0.2 amps (200 milliamps), it is generally safe to open the fuse.
• Induced Current: Induced current tends to fluctuate and not settle on a specific number.
• Fuse Sacrifice Avoidance: Unlike MC4 connectors, avoid sacrificing components at the fuse block.
• Arcing Risk: Opening a fuse under current creates arcs, which can melt surrounding components.
• Alternative Disconnection: If current flow is detected, disconnect the corresponding circuit at the MC4 connector.
• Relieving Circulating Currents: Address circulating currents promptly to prevent overheating and potential fires.
• Potential for Rapid Damage: Catastrophic failures can occur in combiner boxes within 20-30 minutes if circulating currents are left unchecked.

Emergency Procedures and Safety Priorities

• Upstream Disconnection: In case of a melting component, disconnect the circuit upstream (towards the solar panels).
• Gradual Disconnection: When disconnecting, move quickly but avoid running.
• Inverter Disconnection: If the issue escalates, consider disconnecting the inverter or contacting relevant personnel.
• Decision-Making: Complex decisions should be made by experienced personnel.
• DC Voltage Hazard: High DC voltage (e.g., 650 volts) is extremely dangerous. Avoid contact with DC components.
• Arc Flash: Arc flash is a risk associated with DC systems. Wear appropriate protective equipment (e.g., 8 cal suit).
• Shock Hazard Misconceptions: The instructor asserts that the minimum approach distance for shock hazards on combiner boxes is often overstated.
• Distance Mitigation: Distance is a key factor in preventing electrical hazards. DC voltage requires very little to arc across short distances.
• Glove Usage: Electrical gloves may not provide benefit and don't protect against water. Do not interface if it's raining.

Combiner Box Components and Metering

• Fiberglass Hairs: The interior of combiner boxes often contains fiberglass hairs due to resin degradation.
• Ammeter Setting: The ammeter is set to the 400 amp setting initially, since the box is labeled.
• Current Verification: Use a current meter to verify current levels.
• Hot-Cold-Hot (HCH) Verification: Use an ammeter to confirm the expected absence or presence of current at various points in the circuit.

Identifying Ground Faults

• Circulating Currents: Circulating currents in the system indicate potential ground faults.
• Open Circuit Voltage Testing: In an open circuit, ammeter readings are invalid.
• String Voltage Measurement: Measure string voltages, expecting around 730 volts.
• String Voltage Calculation: 730 / 20 = 36.5 meaning the voltage per solar panel is about 36.5V.
• Underground Cable Faults: Common causes of leakage include damage to underground cables, often caused by animals.

Fuse Assessment and High Resistance Failures

• Fuse Failure Impact: Incorrect voltage readings can be caused by a broken