NABCEP NABCEP Solar Heating Installation Professional 2 — Questions and Answers
Question 1: What is the Solar Fraction (SF) of a solar thermal system?
- The angle of the collector relative to true south
- The percentage of the total heating load supplied by solar energy (Correct answer)
- The ratio of collector area to storage volume
- The system's thermal efficiency at standard test conditions
Correct answer: The percentage of the total heating load supplied by solar energy
Solar fraction represents the portion of a building's total water or space heating load that is met by the solar thermal system, with higher values indicating greater solar contribution.
Question 2: Which SRCC (Solar Rating and Certification Corporation) rating is used to compare solar water heating collectors?
- OG-100 Collector Rating (Correct answer)
- OG-300 System Rating
- ISO 9001 certification
- ASHRAE 90.1 compliance
Correct answer: OG-100 Collector Rating
SRCC OG-100 is the collector-level rating that measures thermal performance under standardized conditions, allowing consumers and installers to compare different collector models.
Question 3: In a drainback solar thermal system, what prevents freeze damage when the pump shuts off?
- Antifreeze glycol in the fluid
- The water drains back into an indoor reservoir by gravity when the pump stops (Correct answer)
- An electric heat trace on all outdoor pipes
- Foam insulation on collectors only
Correct answer: The water drains back into an indoor reservoir by gravity when the pump stops
Drainback systems are designed so that water flows only when the pump is running; when the pump stops, gravity returns all water to an indoor reservoir, leaving no water in the collectors to freeze.
Question 4: What is the recommended storage volume per unit collector area for a solar domestic water heating system?
- 1 gallon per square foot of collector
- 1.5–2 gallons per square foot of collector (Correct answer)
- 5 gallons per square foot of collector
- Storage volume has no relationship to collector area
Correct answer: 1.5–2 gallons per square foot of collector
Industry guidelines recommend 1.5–2 gallons of storage per square foot of collector area to ensure adequate thermal mass without oversizing the tank to the point of poor solar fraction.
Question 5: What type of heat exchanger is most commonly used in pressurized closed-loop solar thermal systems to protect potable water?
- Direct open-loop coil
- Double-wall heat exchanger for separation of glycol from potable water (Correct answer)
- Single-wall copper coil submerged in the tank
- Plate heat exchanger with no double-wall requirement
Correct answer: Double-wall heat exchanger for separation of glycol from potable water
Many plumbing codes require a double-wall heat exchanger when toxic antifreeze (or any non-potable fluid) transfers heat to a potable water supply, preventing contamination in case of failure.
Question 6: What sizing tool does SRCC and the solar industry use to estimate annual solar water heating system performance by location?
- ASHRAE load calculator
- F-Chart method or Solar Rating and Certification Corporation OG-300 simulation (Correct answer)
- Manual J residential load calculation
- RETScreen energy analysis
Correct answer: F-Chart method or Solar Rating and Certification Corporation OG-300 simulation
The F-Chart method is the industry standard analytical tool for estimating the annual solar fraction and performance of solar water heating systems using local climate data.
NABCEP NABCEP Solar Heating Installation Professional 2
What is the Solar Fraction (SF) of a solar thermal system?