NABCEP PV System Mechanical Installation 5 — Questions and Answers
Question 1: Which UL standard specifically covers mounting systems (racks and rails) for PV modules?
- UL 1741
- UL 2703 (Correct answer)
- UL 4703
- UL 508A
Correct answer: UL 2703
UL 2703 covers rack mounting systems for flat-plate photovoltaic modules and panels, including bonding and grounding requirements.
Question 2: A roof-mounted PV system has rails running parallel to the roof slope (portrait landscape). This rail orientation is called:
- Landscape racking
- Parallel (portrait) rail configuration (Correct answer)
- East-west racking
- Flush-mount portrait orientation
Correct answer: Parallel (portrait) rail configuration
When rails run parallel to the roof slope with modules in portrait orientation, this is called a parallel or portrait rail configuration.
Question 3: What is the maximum recommended unsupported span for a standard aluminum extrusion rail in most residential PV racking systems?
- 24 inches
- 36 inches
- 48 inches (Correct answer)
- 72 inches
Correct answer: 48 inches
Most residential aluminum rails are rated for spans up to approximately 48 inches between attachment points without exceeding deflection limits.
Question 4: When installing a PV system on a flat roof with a membrane (TPO/EPDM), what is the primary advantage of a non-penetrating ballasted system?
- Lower installation labor cost
- Preservation of the roof warranty by avoiding penetrations (Correct answer)
- Higher wind resistance than penetrating systems
- Reduced need for structural engineering
Correct answer: Preservation of the roof warranty by avoiding penetrations
Ballasted systems avoid puncturing the membrane, which would void most roofing warranties and create potential leak points.
Question 5: What is the primary mechanical hazard when installing PV modules on a steep-slope roof (>8:12 pitch) without proper fall protection?
- Module overheating
- Installer falling from the roof (Correct answer)
- Excessive wind loading on modules
- Fastener corrosion
Correct answer: Installer falling from the roof
Steep roofs dramatically increase the risk of a worker fall, which is the leading cause of fatality in roofing work; OSHA requires fall protection at 6 feet.
Question 6: When adjusting the tilt angle of a ground-mounted PV array from 20° to 30°, what structural effect must be recalculated?
- Module temperature coefficient
- Wind and snow load forces on the racking structure (Correct answer)
- Inverter input voltage range
- Battery state of charge
Correct answer: Wind and snow load forces on the racking structure
Changing tilt angle alters the wind pressure coefficients and snow accumulation patterns, requiring new structural load calculations for the racking.
Question 7: In a dual-tilt (east-west) low-slope racking configuration, what is the primary mechanical advantage over a south-facing single-tilt system?
- Higher annual energy yield per module
- Reduced ballast requirements due to self-anchoring row geometry (Correct answer)
- Lower racking material cost per watt
- Fewer roof penetrations required
Correct answer: Reduced ballast requirements due to self-anchoring row geometry
East-west rows lean against each other, partially self-anchoring and reducing the ballast weight needed to resist wind uplift compared to south-facing rows.
NABCEP PV System Mechanical Installation 5
Which UL standard specifically covers mounting systems (racks and rails) for PV modules?