NABCEP PV System Mechanical Installation 2 — Questions and Answers
Question 1: When installing PV modules on a roof with asphalt shingles, what is the primary purpose of flashing around roof penetrations?
- To improve module aesthetics
- To prevent water infiltration at penetration points (Correct answer)
- To increase structural load capacity
- To reduce wind uplift forces
Correct answer: To prevent water infiltration at penetration points
Flashing directs water away from roof penetrations to prevent leaks and moisture damage to the building envelope.
Question 2: What is the maximum allowable deflection for a rack mounting system under design load conditions per most structural standards?
- L/120
- L/180
- L/240 (Correct answer)
- L/360
Correct answer: L/240
Most racking standards require deflection not to exceed L/240 of the span under design loads to maintain structural integrity.
Question 3: Which fastener type is preferred for attaching aluminum racking to steel purlins in a commercial PV installation?
- Galvanized steel bolts
- Stainless steel bolts (Correct answer)
- Aluminum rivets
- Cadmium-plated screws
Correct answer: Stainless steel bolts
Stainless steel fasteners resist corrosion and are compatible with aluminum racking without causing galvanic corrosion issues when properly isolated.
Question 4: A ground-mounted PV array is located in a region with a frost depth of 42 inches. What is the minimum embedment depth for the support posts?
- 24 inches
- 36 inches
- Below the frost line (Correct answer)
- At the frost line
Correct answer: Below the frost line
Support posts must be embedded below the local frost depth to prevent frost heave from displacing the structure.
Question 5: When using a torque wrench to tighten module clamps, why is it critical to follow the manufacturer's specified torque values?
- To meet electrical code requirements
- To prevent frame damage and ensure proper clamping force (Correct answer)
- To comply with OSHA fall protection rules
- To satisfy utility interconnection standards
Correct answer: To prevent frame damage and ensure proper clamping force
Over-torquing can crack module frames or strip fasteners, while under-torquing results in insufficient clamping force and potential module movement.
Question 6: What is the purpose of a 'mid clamp' in a standard PV racking system?
- To attach the rail to the roof attachment point
- To secure two adjacent modules at their shared frame edge (Correct answer)
- To connect rail sections end-to-end
- To ground the racking system
Correct answer: To secure two adjacent modules at their shared frame edge
Mid clamps are placed between adjacent modules to secure both frames simultaneously to the mounting rail.
Question 7: On a standing-seam metal roof, which attachment method is generally preferred to avoid roof penetrations?
- Lag screws through the seam
- S-5! or equivalent seam clamps (Correct answer)
- Through-bolted L-feet
- Adhesive-bonded mounts
Correct answer: S-5! or equivalent seam clamps
Seam clamps like S-5! clamp directly to the standing seam without penetrating the roof membrane, maintaining the roof's weather integrity.
NABCEP PV System Mechanical Installation 2
When installing PV modules on a roof with asphalt shingles, what is the primary purpose of flashing around roof penetrations?