NABCEP PV System Mechanical Installation 4 — Questions and Answers
Question 1: What is the minimum required fire setback distance from a ridge line for rooftop PV systems in many jurisdictions adopting IFC requirements?
- 12 inches
- 18 inches
- 3 feet (Correct answer)
- 6 feet
Correct answer: 3 feet
The International Fire Code requires a minimum 3-foot setback from ridge lines to allow firefighter access and ventilation during a fire.
Question 2: When modules are installed in a landscape orientation versus portrait orientation on the same racking system, what mechanical consideration changes?
- Grounding requirements
- Module wiring polarity
- Clamp placement and rail spacing (Correct answer)
- Inverter sizing
Correct answer: Clamp placement and rail spacing
Changing orientation affects the module dimension spanning between rails, requiring adjusted rail spacing and clamp positioning.
Question 3: What is the function of a 'wire management clip' or 'cable clip' used in PV installations?
- To terminate PV wiring at the combiner box
- To organize and secure DC wiring to the racking rail to prevent abrasion (Correct answer)
- To connect module frames for grounding
- To label individual circuit conductors
Correct answer: To organize and secure DC wiring to the racking rail to prevent abrasion
Cable clips secure conductors to rails, preventing movement that causes chafing, abrasion damage, and potential faults.
Question 4: Which standard governs the structural design loads (wind, snow, seismic) that must be applied to PV mounting systems in the United States?
- UL 2703
- ASCE 7 (Correct answer)
- IEC 61215
- NEC Article 690
Correct answer: ASCE 7
ASCE 7 (Minimum Design Loads and Associated Criteria) specifies the wind, snow, and seismic loads used for structural design of PV mounting systems.
Question 5: A carport-style ground mount PV system must support vehicle loads below and PV above. What additional structural consideration is required compared to a standard ground mount?
- Deeper rail embedment only
- Increased column sizing and cross-bracing to handle combined gravity and lateral loads (Correct answer)
- Additional module clamps per rail
- Fire-rated conduit throughout
Correct answer: Increased column sizing and cross-bracing to handle combined gravity and lateral loads
Carport structures must carry both the PV array loads and provide overhead clearance, requiring heavier column design and lateral bracing for wind and seismic loads.
Question 6: When using a hammer drill to install lag screws into roof rafters, what step should be taken first to ensure structural integrity?
- Pre-drill a pilot hole slightly smaller than the lag screw shank (Correct answer)
- Use the lag screw directly without pilot hole for maximum grip
- Apply sealant before drilling
- Install the flashing before drilling
Correct answer: Pre-drill a pilot hole slightly smaller than the lag screw shank
A pilot hole prevents wood splitting and guides the lag screw into the center of the rafter for maximum pull-out strength.
Question 7: What is the purpose of applying butyl tape or roofing sealant around a lag bolt after installation in a composition shingle roof?
- To increase pull-out strength of the fastener
- To create a watertight seal around the roof penetration (Correct answer)
- To satisfy electrical bonding requirements
- To prevent UV degradation of the lag bolt
Correct answer: To create a watertight seal around the roof penetration
Sealant or butyl tape fills the gap around the fastener penetration to prevent water infiltration into the roof structure.
NABCEP PV System Mechanical Installation 4
What is the minimum required fire setback distance from a ridge line for rooftop PV systems in many jurisdictions adopting IFC requirements?