The Most Common Issues Found During Solar Commissioning

Commissioning is a critical phase of any solar project, as it serves as the final verification process before a site is energized and handed over to the owner. A comprehensive commissioning process verifies that the project meets design specifications, safety requirements, and performance expectations.

Photo by Day Electric

Unfortunately, not all systems are built with proper QA/QC checks along the way and along with the pressure of construction timelines, commissioning inspections frequently uncover issues that impact production, pose safety hazards, or lead to costly repairs if left unaddressed.

Before we dig in, let’s address the most common issue we face BEFORE starting the commissioning process as an experienced 3^rd party commissioning contractor. Most commonly, we face sites not actually being ready for commissioning when being asked to dispatch to site. Usually this is the result of miscommunication between on-site crews and management, and is a common occurrence we face. This can usually be solved by a pre-commissioning inspection to assess site conditions to prepare for commissioning, or an in-house individual that is on-site that can provide reliable feedback of site readiness. The commissioning process takes communication and transparency from all parties for it to go smoothly.

The commissioning process is a set of inspection and testing measures to verify a system is built, executed, and performing as expected, safely, with no known risks. As an experienced 3^rd party commissioning expert, we asked our commissioning technicians what the most common issues found during the commissioning process are and compiled our list of the top 10 issues found:

1. DAS/SCADA Not Communicating

Monitoring issues can prevent operators from identifying production or equipment failures promptly, so it is essential they are communicating before a site is handed over. This is a common issue found during commissioning that often needs to be remediated by an experienced commissioning technician well-versed in this area.

2. Tracker Issues

Most commonly, trackers not tracking properly. This will usually be called out during mechanical completion in the initial inspection for corrections to be made. When trackers are operating properly, they maximize the amount of sunlight hitting the panels, thus increasing production. On a large solar farm, a tracker row that is not tracking properly, or even off slightly, can lose a noticeable amount of energy production and revenue over time.

3. Incorrect Inverter Settings

During commissioning, inverter settings often need to be adjusted to meet utility interconnection requirements or project-specific operating criteria. The goal is to ensure the plant operates safely, complies with grid requirements, communicates correctly with control systems, and delivers the expected performance before commercial operation begins.

4. Loose Terminations

The commissioning process is usually the first time the entire electrical system is thoroughly inspected, tested, and energized under real operating conditions. On a utility-scale solar site, you may see thousands of electrical terminations; therefore, there are numerous spots for error to occur. Whether it’s vibration, thermal expansion, or human error, it is a very common issue to find during commissioning and important to correct. Loose terminations can cause excessive heating, arcing, fire hazards, equipment damage, and/or reduced system efficiency.

5. Discrepancies between plans and onsite equipment

A major component of commissioning is to check and verify that a system matches construction plans, concerning design, layout, and equipment. With so many contractors involved, miscommunication, and human error, it is common for there to be discrepancies between plans and what is discovered during the visual inspection portion of commissioning. Sites need to be built, as they were designed and engineered, to reduce risk of errors.

6. Damaged Equipment

Every system is composed of a large amount of material and equipment, from modules, inverters, combiner boxes, SCADA, switchgear, etc. All of these components are at risk of damage occurring and needing correction before project completion. Equipment damage can occur from manufacturing defects, transportation, site and storage conditions, installation quality, construction activities, and the environment. Between visual and mechanical inspections and various testing measures , like thermal imaging, insulation resistance testing, etc., damaged equipment can be called out and replaced or corrected during the commissioning process to prevent larger repairs or production declines in the future.

7. Incomplete Grounding

Grounding is critical for the safety of personnel and equipment, however it can often be overlooked or improperly performed and/or completed. Since grounding components are installed throughout multiple phases of construction, it is not uncommon for it be overlooked. It is often discovered that grounding connectors have not been installed or connected to equipment, such as combiner boxes or transformers. This error leaves equipment vulnerable to electrical faults. Incomplete grounding can be discovered by commissioning technicians performing continuity or ground resistance testing.

8. DC Wiring and String Issues

DC wiring and string issues are common finds during commissioning due to the large quantity of modules, wiring, and electrical connections. Since solar projects are built under demanding schedules, with multiple contractors involved, wiring errors can occur often due to incomplete string installation, pinched conductors, damaged cable, incorrect string connections, etc. Most wiring and string issues are discovered through testing, such as VOC testing, as they are often difficult to identify solely through a visual inspection.

9. Poor MC4 Connector Installation

MC4 connectors are among the most widely used electrical connections used on solar sites. They connect DC wiring to the module and often face installation issues due to improper cable stripping or crimping techniques, damaged connector components, rushed installation, or human error. Because every string relies on multiple MC4 connections, a single defective connector can impact the performance of an entire circuit. For this reason, it is important they be corrected during the commissioning process and can be identified through visual inspections, thermal imaging, IV curve tracing, or voltage testing.

10. Vegetation Overgrowth or Overall Poor Site Conditions

Mowing and vegetation control can often be overlooked during construction, as it is often looked at as an O&M activity. However, vegetation management is important to address throughout the construction lifespan, to ensure safe working conditions for crews. It is also important to address site cleanliness, water build-up, or other issues affecting overall site conditions that may impact safety, site access, or cause production concerns down the road.

The commissioning process, comprised of visual and mechanical checks, as well as system-wide testing, allows all parties involved to know a project is safe, reliable, and able to be handed over to the owner. Best-case scenario, commissioning is performed by a 3^rd party contractor specialized in inspection and testing. This provides unbiased, reliable, and verified documentation, essential for the owner, and beneficial to EPCs looking to limit liability. Commissioning is also a process that needs special attention to detail, as it is the final check before a project reaches completion; nothing can be overlooked. When commissioning is not prioritized and rushed, you often see systems that face production and safety concerns within the first few years of operation. This results in higher O&M costs and less revenue for the owner down the road.

“When it comes to commissioning, it’s important to understand that it shouldn't be rushed just to get a project across the finish line. It's more than just ‘turning it on’. Our job is to make sure everything is installed correctly and safely; if you rush that process, you risk damaging the equipment, or worse, you risk the health and safety of individuals working on site.” -Drake, Commissioning Technician at Day Electric

At Day Electric, we perform 3^rd party commissioning and testing services to support EPCs and owners. We understand the importance of thorough inspections, complete system testing, and reliable and comprehensive reporting. It’s not about rushing to get a project over the finish line, it is about the long-term safety and reliability of a system.

Want to learn more about commissioning, or in need of a 3^rd party commissioning contractor? Contact Day Electric for more information.