OBJECTIVESOBJECTIVES

1. Identify the three general steps required for the diagnostics and troubleshooting of PV systems and demonstrate knowledge of their use.2. Identify PV system maintenance requirements and demonstrate service procedures for modules, arrays, batteries, power conditioning equipment, safety systems, and weather sealing systems.3. Demonstrate how to measure PV system performance and compare with specifications.4. Demonstrate how to perform PV diagnostic procedures and troubleshooting skills.5. Demonstrate how to identify PV performance safety issues, and implement corrective measures.6. Demonstrate how to test and verify PV system installation functionality and integrity using proper wire labeling, wire mapping, wire placements, input/output verifications, and prior documentation.7. Demonstrate when to communicate with technical support, and what information is relevant.

(continued)

OBJECTIVES (CONTINUED)OBJECTIVES (CONTINUED)

8. Compile, maintain, and deliver appropriate manuals and documentation (records of system operation, performance, and maintenance activities) to the client upon the completion of the PV installation.9. Identify demarcation issues, along with the responsibilities of associated trades and/or utilities.

Has it been cloudy for several days? Maybe the battery bank simply needs recharging.

Is the array blocked (shaded) by something, or is it dirty?

Are any fuses or circuit breakers blown or tripped?

If the PV system fails, determine:

Any loose connections?

Are any connections corroded?

Is the wiring system operating with proper polarity?

(continued)

Is the system operating under proper voltage and current?

Are the modules and batteries properly connected (series and parallel configuration)?

Are any of the components physically damaged?

If the PV system fails, determine: (continued)

Analyze the problem thoroughly enough to be able to create a clear problem statement. With a clear problem statement in mind, define the observed symptoms and their potential causes.

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Gather enough facts in order to help isolate the possible causes of the problem.

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Consider the possible problem causes based on the facts gathered.

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The following steps help to round out the general problem-solving process.

(continued)

Create an action plan based on those causes. Begin with the most likely problem, and devise a plan in which only one variable will be manipulated.

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Implement the action plan, performing each step carefully while testing to see whether the symptom disappears.

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Analyze the results to determine whether the problem is resolved.

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The following steps help to round out the general problem-solving process. (continued)

(continued)

Terminate the process if the problem is resolved.

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If the problem is not resolved, create an action plan based on the next most probable cause, and return to Step 4 to repeat the process until the problem is solved.

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The following steps help to round out the general problem-solving process. (continued)

Figure 7-1: Digital Multimeter

Figure 7-2: DC Voltage Check

WARNINGWARNING

When setting the meter, it is normal practice to first set the meter to its highest voltage range, to make certain that the voltage level being measured does not damage the meter.

Figure 7-3: Testing an Outlet

WARNINGWARNING

Remember to keep the power off. Unlike the voltage check, resistance checks are always made with power removed from the system.

Figure 7-4: Measuring Current

The various sections of a photovoltaic system include components such as:

Photovoltaic cells. These are thin squares, discs, or films of semiconductor material that generate voltage and current when exposed to sunlight.

Panels. These are various configurations of individual PV cells, laminated between a clear glazing.

(continued)

The various sections of a photovoltaic system include components such as: (continued)

Arrays. These consist of one or more panels, wired together to provide a specific voltage. Figure 7-5 illustrates how cells, modules, panels, and arrays are related.

Charge controllers. These are equipment components that regulates battery voltage.

Battery storage. The medium used to store direct current electrical energy.

(continued)

Figure 7-5: Photovoltaic Cell, Module, Panel, and Array Example

The various sections of a photovoltaic system include components such as: (continued)

Inverters. These are electrical devices that change direct current into alternating current.

DC loads. These are appliances, motors, and equipment powered by direct current.

AC loads. These are appliances, motors, and equipment powered by alternating current.

The various arrangements of PV modules and panels include:

Strings. A string consists of a number of PV panels connected in series.

Arrays. An array consists of a number of PV strings connected in parallel.

Figure 7-6: Cleaning the PV Module

Figure 7-7: Partial Shading of a 36-Cell PV Module

Figure 7-8: A Combiner Box

Voltages between strings should match closely when the sunlight is consistent. Keep the following key points in mind:

NEC 690.7(A) requires that the open circuit voltage be multiplied by a correction factor based on the lowest expected ambient temperature.

Convention dictates that the lowest expected ambient temperature is the same as the minimum recorded temperature.

Voltages over 600V are not permitted in one and two family dwellings, as per NEC690.7(C).

(continued)

Voltages between strings should match closely when the sunlight is consistent. Keep the following key points in mind: (continued)

For the majority of New York State, if the nominal Voc is over 480Vdc then the system will exceed the 600V limit.

Voc over 600Vdc can damage inverters, insulation, and switchgear.

Open circuit voltage of PV panels is temperature dependent, generally –0.4%/° C.

(continued)

Voltages between strings should match closely when the sunlight is consistent. Keep the following key points in mind: (continued)

Voc is not a strong function of irradiance and it comes up pretty quickly at dawn before any direct radiation hits or heats the PV modules.

Night sky radiation actually cools the modules a few degrees below the ambient temp and that is why you get frost above 32° F.

The lowest daily temperatures generally occur just before sunrise.

Table 7-1: Color Coding for AC and DC PV Circuits

Figure 7-9: Multi-contact PV Connectors

Figure 7-10: A Solarlok Junction Box

Figure 7-11: Huber+Suhner Connectors

Table 7-2: IP Ratings

Figure 7-12: A Basic PV Wiring Example

Figure 7-13: PV System Fuses for 600Vdc and 1000Vdc Systems

Figure 7-14: Normal PV Module Operations

Figure 7-15: A Shaded PV Module Hot Spot with No Bypass Diodes

Figure 7-16: A Shaded PV Module Hot Spot with Bypass Diodes

Figure 7-17: Module IV Curves With and Without Bypass Diodes

Figure 7-18: Bypass Diodes Housed In Module Junction Boxes

Blocking reverse current flow from the battery through the module at night. In battery charging systems, the module potential drops to zero at night, and the battery could discharge all night backwards through the module. This would not be harmful to the module, but would result in loss of precious energy from the battery bank. Diodes placed in the circuit between the module and the battery can block any nighttime leakage flow.

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Two situations in which blocking diodes can help prevent the phenomenon include:

(continued)

Blocking reverse current flow through damaged modules during the day, originating from parallel modules. In high-voltage systems during daylight conditions, blocking diodes can be placed at the head of separate series-wired strings. If one string be comes severely shaded, or if there is a short circuit in one of the modules, the blocking diode prevents other strings from losing current backwards through the shaded/damaged string. The shaded/damaged string is “isolated” from the others, and more current reaches the load. In this configuration, blocking diodes are called “isolation diodes.”

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Two situations in which blocking diodes can help prevent the phenomenon include: (continued)

If the voltage level is too low at the point where the battery storage system connects to the PV system, then there are several options to consider:

The PV system is not supplying enough current to the battery system to keep it charged up – a PV panel or string is not functioning, the disconnect(s) are open, one of the monitoring devices is faulty, or an overcurrent device has blown or tripped.

(continued)

If the voltage level is too low at the point where the battery storage system connects to the PV system, then there are several options to consider: (continued)

One or more of the batteries in the system is failing – when a cell within a battery fails, the entire battery may fail (refusing to take a charge) or it may simply produce a lower than specified output voltage. In either case, you will have to isolate the defective battery and replace it with a working one. In complex storage systems, this will involve isolating the terminals of each battery one-by-one to test its output.

(continued)

If the voltage level is too low at the point where the battery storage system connects to the PV system, then there are several options to consider: (continued)

There has simply not been enough light present to produce sufficient output to charge the battery storage system – check for dirty panels or shading that may be diminishing the output of the PV array.

Figure 7-19: Battery Storage System Connection Point

If the input voltage is correct, but no (or improper) output voltages are present, there are several possibilities to consider:

The battery storage system is configured improperly (incorrect series-parallel connections)

(continued)

There are bad connections or devices between the charge controller and the battery storage system, causing the charge controller to not sense the presence of the batteries (charge controllers shut down when no load is connected to them)

If the input voltage is correct, but no (or improper) output voltages are present, there are several possibilities to consider: (continued)

One or more of the batteries in the storage system are defective

The Charge Controller is defective (or it could be incorrectly sized for the panel array/battery storage system configurations)

Figure 7-20: A Simple Charge Controller

Figure 7-21: Load Diverter Duties

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include:

The battery storage system is configured improperly (incorrect series-parallel connections). Verify the battery system configuration and rewire as necessary to achieve the correct configuration.

(continued)

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include: (continued)

There are bad connections or devices between the inverter and the battery storage system (or the charging controller), causing excessive voltage drop between the battery system and the inverter. Make sure the cabling is large enough to handle the current flow from the battery storage system or the PV system. Tighten all the connections between the batteries and the inverter.

(continued)

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include: (continued)

One or more of the batteries in the storage system are defective. Replace the battery with a working unit.

(continued)

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include: (continued)

The inverter’s load is too large and is pulling AC current out of the inverter faster than the battery/PV array systems can produce DC current to replace it. Disconnect the load and check the output of the inverter without it. Manually reset the unit by turning it off and then back on.

(continued)

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include: (continued)

The Charge Controller or Diverter/Regulator output voltage is too high, causing the inverter to shut down for self-protection purposes.

(continued)

If the inverter’s input voltage to the inverter is low (or missing), check the battery storage system to determine the cause of the low voltage. Possible causes can include: (continued)

The input vents for the inverter’s fan may be clogged causing it to shut down due to overheating - clear the vents so that cooling air can move freely through the inverter. Allow the inverter to cool off before restarting it.

CAUTIONCAUTION

Always make sure to disconnect the AC source before disconnecting any of the DC connections.

Documentation that was originally organized or created by the installation team, or previous repair personnel.

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Troubleshooting documentation exists in two categories:

Documentation that you, the troubleshooting technician must generate during any repair scenario.

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Figure 7-22: A Residential Solar PV Wiring Diagram with Overlay

Figure 7-23: A Cable Tester