Installation Standards

The ultimate goal of reducing PV costs to grid parity requires a substantial reduction in installation costs. Development of industry-wide installation standards should support this goal. A key area where standardization of methods can help is in reduction of compliance costs. A reduction in the incidence of rejections by building inspectors will reduce the overall costs of installation, as well as the uncertainty in estimating labor and administrative costs.

Objectives

The SolarTech group intends to document a set of best practices for installation, specifically targeted at enabling installers to pass inspection on the first visit. This documentation will clarify the requirements of the NEC Code as it relates to solar installations and will highlight the differences in requirements imposed by inspectors and building departments in different jurisdictions within Silicon Valley.

The documentation produced in this effort is intended to be utilized by installers to aid in their job planning and training processes. It is also intended to support the installer training programs defined in this paper. Furthermore, it will provide the building departments with a set of benchmarks, to encourage and empower them to adopt standard methodologies that will reduce costs of compliance within their jurisdictions.

Focus on Compliance Costs

Many solar installers have been in business for many years, and have developed their own installation practices that enable them to be very efficient in their operations. However, there is some reluctance to share many of their hands-on techniques with competitors.

One area where all installers can benefit from sharing such information is in reducing compliance costs. All installers have stories of building inspectors’ rejections. Furthermore, the more experienced installers learn to tailor their techniques to the particular requirements of local jurisdictions, often driven by the opinions or preferences of specific inspectors.

A major cost driver of solar installations is the number of trips to the job site that are required to complete the job. A failed inspection costs another trip. Eliminating unnecessary trips to the jobsite and eliminating rejections by the inspector are common goals that have universal appeal.

A worthy initial goal is to enable a high percentage (99 percent) of solar installations to be approved on the first visit of the building inspector. However, a more interesting long-term goal is to work towards eliminating the inspection visit altogether – by enabling experienced, high quality installers to self-inspect and commission their own systems through a Permit by Rule process similar to that which is used for water heater and pool equipment installations. It is a secondary goal of SolarTech to investigate the process by which a certification path can be developed to deliver this capability.

Best Practices Approach

The central deliverable of the SolarTech installation standards effort will be an installation Best Practices Guide, designed to enable solar installers to pass a building inspection on the first attempt. In addition to the printed form, this guide will be incorporated into a website, to enable it to be maintained as a living document and to enable its content to be filtered or tailored to the user’s jurisdiction.

The documentation effort will focus on potential problem areas where inspectors have been known to raise issues. It is intended to be highly specific and hands-on and will include a photo gallery of specific installation practices implemented in a variety of settings.

In the process of developing these best practices, the team will review the content with the departments having jurisdiction in Silicon Valley, and will partner with the departments to drive continuous process improvement over time. Periodic reviews with the building departments will enable the building inspectors and permitting authorities to review and comment on the best practices as proposed and will highlight differences between jurisdictions to empower building departments to simplify their requirements based on an understanding of common practices in other local jurisdictions.

Upon completion of the guide, its content is intended to be incorporated into the installer training programs to be developed by SolarTech discussed separately in this paper. Furthermore, the Guide provides a long term opportunity to collaborate with International Association of Electrical Inspectors (IAEI) to expand/define nationwide best practices for solar installers and inspectors.

Key Potential Areas for Cost Reduction

A number of specific areas for best practices development have been identified by SolarTech:

• Grounding: Per the NEC code, modules with metal frames and metal mounting structures must be grounded. The specific methods for grounding, ground rod placement, and wiring methods vary, and significant opportunities for standardization and cost reduction exist.
• Inverter selection, connection and placement: Inverters convert DC power from solar modules into AC power that can be used or fed back into the utility grid. In most cases, inverters that are UL-listed are acceptable; however, some utilities and some building departments place additional requirements on inverter selection. In placement of inverters, which is subject to the design of the building and placement of the PV panels, the guide will highlight universal good practices, such as placement in the shade, providing adequate airflow, and minimizing wire losses.
• Disconnects & disconnect placement: Disconnects for both AC and DC power are typically employed in a solar installation and are also incorporated into some inverters. These allow the system to be safely turned off for maintenance or by emergency personnel. Jurisdictions and utilities, however, have widely different requirements for the location, type, and placement of disconnects. As of November 2006, PG&E no longer requires AC disconnects in most residential installations; however, other utilities still require them. Also, Santa Clara County no longer requires DC disconnects because some inverters have an integrated-disconnect switch ; however, other jurisdictions still require DC disconnects that are external to the inverter.
• Wiring & conduit: The wiring between solar modules and the inverter is generally contained in conduit. The type of conduit, penetration of the conduit through living spaces and walls, and other specific wiring hardware are subject to interpretation of the National Electrical Code (NEC) but have resulted in many opportunities for disagreement with building inspectors. For example, under the 2005 version of the NEC, DC conduits are allowed in attics but are not allowed under the 2002 version of the NEC. Many building departments are still using the 2002 version and have not adopted 2005, creating challenges for installers.
• System labeling: The NEC provides specific requirements for labeling of wiring, inverters, and disconnects; however, some local jurisdictions have differing preferences and standards. Labeling should be a low-cost part of the installation, with standards that prevent if from becoming cause for rejection by an inspector.

Other Installation Cost Drivers

There are some cost drivers in PV installations where standardization efforts may be less likely to help, but where product innovation and experience will provide eventual cost reductions. Mounting of the PV modules to the roof or other structure is one of the most significant costs in an installation and is subject to many variations in technique and in products used. Standardization would require installers to agree to use only a single kind of racking, for example. While there will likely never be universal agreement on a single mounting solution, there could be benefits in providing best and recommended practices information for voluntary adoption by integrators and installers.

Job cost estimation, design, and pricing is another area where installers use many different approaches. Sophisticated installers tend to develop their own estimating software, which becomes a key advantage in managing costs. A well-designed software package for PV system design and cost estimation would enable many more installers to reap these benefits. While this is a commercial undertaking best left to third parties or individual companies, there would be benefits in sharing information on rebates, solar assessments, equipment specifications and the like, as well as the potential of hosting an open source forum for sharing software source code.

Summary of Recommendations

In order to develop a Best Practices Guide, SolarTech will build a multi-disciplinary team, including installers, distributors, module, rack, and inverter suppliers, and municipalities/inspectors. The team will also include professionals to conduct the research, photography, documentation and web development required.

The team will develop surveys (to be done in interview form) for building departments, installers, and equipment suppliers. The surveys will focus on several key areas:

1. Parts of the installation that have generated rejections by inspectors.
2. Differences in requirements among jurisdictions.
3. Practices that installers have developed to accommodate the inspectors’ requirements and to assure passing inspection on the first visit.

Since the initial focus of SolarTech is on installations in Silicon Valley, the team will identify the appropriate jurisdictions and will identify installers who have completed installations in each. The research will include meeting with installers and visiting jobsites to photograph installations and build a photo library. In addition, the team will hold monthly meetings to discuss findings and solicit feedback from member companies.

The Best Practices Guide will be an online resource to ensure it serves as a living document and to enable its content to be customized by jurisdiction. The content will include an online database of specific city/county restrictions, interpretations, requirements, and preferences. An installer should be able to visit the site before doing an installation in a new city and print out a guide defining specifically what needs to be done in order to install a system in that city that will pass inspection.

The Best Practices Guide is intended to enable installers to minimize the number of trips they must make to the jobsite, as well as to the city offices. Combining this effort with SolarTech’s permitting and workforce efforts provides a multi-faceted approach that will reduce compliance costs and help the industry move closer to the goal of single-visit installations.