NABCEP - Certified North American Board of Certified Energy Practitioners Specialist PV System Mechanical Installation Questions and Answers — Questions and Answers
Question 1: When installing a PV array on a composite shingle roof, what is the primary purpose of using flashing at each roof penetration?
- To provide a secure bonding path for the equipment grounding conductor.
- To cover the lag screw heads for aesthetic purposes.
- To divert water away from the penetration point and prevent leaks. (Correct answer)
- To increase the pullout strength of the lag screws securing the L-feet.
Correct answer: To divert water away from the penetration point and prevent leaks.
Flashing is a critical component for weatherproofing roof penetrations. It is installed over the L-foot or standoff and integrated with the roofing material (shingles) to create a watershed that directs water away from the hole created for the lag screw, thereby preventing water intrusion and potential roof leaks.
Question 2: An installer is using a torque wrench to tighten the M8 bolts on the mid-clamps securing PV modules to the racking system. The racking manufacturer's instructions specify a torque value, but the module installation manual provides a different, lower torque range. Which torque specification should the installer follow?
- The higher value to ensure maximum clamping force.
- The average of the two specified torque values.
- The torque specification from the racking manufacturer.
- The torque specification from the PV module manufacturer. (Correct answer)
Correct answer: The torque specification from the PV module manufacturer.
The PV module frame is the more sensitive component. Overtightening the clamps can deform the module frame, create stress points on the glass, and potentially void the module warranty. Therefore, the installer must adhere to the torque values specified by the module manufacturer to avoid damaging the product.
Question 3: Which of the following is a key requirement when using a UL 2703 listed mounting system to bond the PV modules together?
- A separate grounding electrode must be installed at the array location.
- A bare copper bonding jumper must connect each individual module frame.
- The system must be installed precisely according to the manufacturer's instructions. (Correct answer)
- Each rail segment must be connected to the grounding electrode conductor.
Correct answer: The system must be installed precisely according to the manufacturer's instructions.
A UL 2703 listing certifies that a racking system and its components provide a reliable bonding path when installed as a complete system. This certification is contingent upon following the manufacturer's specific installation instructions, which detail how components like clamps and splices create the electrical bond. Deviating from these instructions can compromise the integrity of the bonding path.
Question 4: A PV system is being installed on a roof in a region with high snow loads. According to ASCE 7 standards, what factor is critical for determining the design snow load on the array?
- The color of the roof shingles.
- The ambient air temperature during installation.
- The ground snow load for the specific location. (Correct answer)
- The brand of the PV module being installed.
Correct answer: The ground snow load for the specific location.
The American Society of Civil Engineers (ASCE) 7 standard, "Minimum Design Loads for Buildings and Other Structures," is the basis for structural design requirements. The starting point for calculating roof snow loads is the ground snow load (pg), which is determined from maps based on historical climate data for the specific geographic location.
Question 5: When attaching a flush-mounted racking system to a residential roof, what is the standard best practice for securing the L-feet or standoffs?
- Attaching them directly to the roof decking with wood screws.
- Securing them with adhesive approved for roofing applications.
- Using lag screws driven into the center of the roof rafters. (Correct answer)
- Placing them between shingles without any roof penetration.
Correct answer: Using lag screws driven into the center of the roof rafters.
To ensure the structural integrity of the PV array and its ability to withstand wind and snow loads, the racking system must be securely anchored to the building's structure. The standard and required practice is to locate the roof rafters and drive lag screws through the roof decking and into the center of these structural members, providing a strong and reliable connection.
Question 6: During a mechanical installation, an installer notices that removing a single PV module from the middle of a row will break the continuity of the equipment grounding conductor run along the rail. According to NEC and best practices, this installation is:
- Acceptable, as long as the module is immediately replaced.
- Non-compliant, because removing a module must not interrupt the bonding path for other modules. (Correct answer)
- Compliant, provided the inverter has integrated ground-fault protection.
- Acceptable, if the modules are mounted on a non-conductive roof surface.
Correct answer: Non-compliant, because removing a module must not interrupt the bonding path for other modules.
NEC 690.43 and best practices require that the equipment grounding path for a PV array remains continuous. The connection method for the bonding jumpers or grounding clips must be arranged so that the removal of a single module does not interrupt the grounding continuity for any other modules in the array. This ensures the entire system remains safely grounded during maintenance.
NABCEP - Certified North American Board of Certified Energy Practitioners Specialist PV System Mechanical Installation Questions and Answers
When installing a PV array on a composite shingle roof, what is the primary purpose of using flashing at each roof penetration?