CSLB C-46 Solar (Trade Exam) — All Questions
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18 questions
Which passive solar water heating system stores the water inside the collector itself?
- a.Indirect active system
- b.Integral collector-storage (batch)✓
- c.Evacuated-tube active system
- d.Direct active system
DOE describes integral collector-storage systems as a storage tank covered with transparent material so the sun heats the water in it. Active systems use pumps; ICS systems suit mild-freeze climates.DOE Energy Saver, Solar Water Heaters
In a one-tank solar water heating system, where is the backup heater?
- a.On the roof beside the collector
- b.In a separate tank downstream
- c.There is no backup in one-tank systems
- d.In the same tank as solar storage✓
DOE explains that in one-tank systems the backup heater is combined with the solar storage in one tank; in two-tank systems the solar tank preheats water for a conventional heater.DOE Energy Saver, Solar Water Heaters
How many Btu does it take to heat 40 gallons of water from 60 °F to 120 °F, using DOE's 8.35 pounds per gallon?
- a.About 20,040 Btu✓
- b.About 334 Btu
- c.About 2,400 Btu
- d.About 40,080 Btu
DOE's formula is gallons × 8.35 × temperature rise: 40 × 8.35 × 60 = 20,040 Btu. Leaving out the 8.35 pounds per gallon gives 2,400, which treats water as weighing one pound per gallon.DOE Energy Saver, Estimating the Cost and Energy Efficiency of a Solar Water Heater
What range of collector area does DOE give for solar pool heating, relative to the pool's surface area?
- a.150 to 200 percent of the surface area
- b.Exactly equal to the pool's volume in gallons
- c.50 to 100 percent of the surface area✓
- d.10 to 25 percent of the surface area
DOE says the surface area of the solar collector should equal 50 to 100 percent of the pool's surface area, more in cooler and cloudier areas and less with a pool cover.DOE Energy Saver, Solar Swimming Pool Heaters
How can a solar pool heating system help cool a pool in a hot climate?
- a.By adding glycol to the pool loop
- b.By reversing the pump at noon
- c.By circulating water through them at night✓
- d.By draining the collectors during the day
DOE notes that in hot climates the collectors can cool the pool during peak summer months by circulating water through them at night.DOE Energy Saver, Solar Swimming Pool Heaters
A pool holds 1,500 cubic feet of water. About how many gallons is that?
- a.About 11,220 gallons✓
- b.About 55 gallons
- c.About 1,500 gallons
- d.About 200 gallons
NIST defines a gallon as 231 cubic inches and a cubic foot as 1,728 cubic inches, so one cubic foot is about 7.48 gallons: 1,500 × 7.48 ≈ 11,220 gallons. Fifty-five is the volume in cubic yards.NIST Handbook 44 Appendix C
Which collector has parallel rows of transparent glass tubes and is used more often in U.S. commercial applications?
- a.Thermosyphon batch tank
- b.Evacuated-tube collector✓
- c.Unglazed flat-plate collector
- d.Integral collector-storage unit
DOE describes evacuated-tube collectors as parallel rows of transparent glass tubes, each with an absorber tube and fin, and says they are used more frequently for U.S. commercial applications. Unglazed collectors are typical for pools.DOE Energy Saver, Solar Water Heaters
Where should integral collector-storage (batch) systems be installed, according to DOE?
- a.Indoors in the attic
- b.Anywhere; the tank is insulated
- c.In climates with regular hard freezes
- d.Only in mild-freeze climates✓
The stored water sits outdoors in the collector, so DOE says ICS systems belong only where freezes are mild. Insulation does not protect outdoor pipes in severe cold. Hard freezes are exactly where the outdoor pipes would freeze. An attic location would not let the collector heat the water.DOE Energy Saver, Solar Water Heaters
What does the solar energy factor of a solar water heater measure?
- a.Hours of sun per year at the site
- b.Collector area per gallon of storage
- c.Energy delivered divided by energy put in✓
- d.The share of the load supplied by the sun
DOE defines the solar energy factor as the energy delivered by the system divided by the electrical or gas energy put into it. That describes the solar fraction, which is a different rating. Collector area per gallon is a sizing ratio. Sun hours describe the climate, not the system's rating.DOE Energy Saver, Estimating the Cost and Energy Efficiency of a Solar Water Heater
Why are double-wall heat exchangers less efficient than single-wall ones?
- a.They are required to run at lower flow rates
- b.They use noticeably less copper tubing
- c.Heat must cross two surfaces, not one✓
- d.They hold more antifreeze in the jacket
DOE explains that heat must pass through two surfaces rather than one, which lowers efficiency. Copper quantity does not explain the loss. Flow rate is not the reason given. Antifreeze volume is not the reason given.DOE Energy Saver, Solar Water Heaters
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A solar water heating system's daily load is 34,120 Btu. About how many kilowatt-hours is that, at 3,412 Btu per kWh?
- a.About 100 kWh
- b.About 1 kWh
- c.About 10 kWh✓
- d.About 3.4 kWh
34,120 divided by 3,412 is 10 kWh. 100 kWh moves the decimal point the wrong way. 1 kWh divides by 34,120 instead of 3,412. 3.4 kWh divides 34,120 by 10,000.EIA, Energy conversions (Btu per kWh)
What is a drawback of air as a solar heat-transfer fluid, according to DOE?
- a.It is toxic in small amounts
- b.It corrodes copper tubing quickly
- c.It freezes solid at 20 degrees F
- d.Its heat capacity is very low✓
DOE notes air will not freeze or boil and is non-corrosive, but has a very low heat capacity. Air does not freeze in a collector loop. Air is not toxic. Air is non-corrosive.DOE Energy Saver, Solar Water Heaters
How does a pool cover affect the collector area needed for solar pool heating?
- a.It requires glazed collectors instead
- b.It usually decreases the required area✓
- c.It increases the required collector area
- d.It has no effect on the area needed
DOE says you can usually decrease the required collector area by using a pool cover. A cover reduces heat loss, so it lowers the need for area. A cover does change heat loss, so it does have an effect. A cover does not change the collector type.DOE Energy Saver, Solar Swimming Pool Heaters
A pool slopes uniformly from 3 feet deep at one end to 9 feet deep at the other. What average depth is used to find its volume?
- a.3 feet
- b.9 feet
- c.6 feet✓
- d.4.5 feet
For a uniform slope the average is (3 + 9) / 2 = 6 feet. 3 feet is only the shallow end. 9 feet is only the deep end. 4.5 feet halves the deep end alone.NIST Handbook 44 Appendix C (volume units)
Which pool collector costs more but works better in cold weather and can also heat domestic water, per DOE?
- a.An unglazed rubber collector on the roof
- b.A glazed copper collector✓
- c.A black plastic drum set on the roof ridge
- d.A bare black plastic hose loop on the roof
DOE describes glazed collectors of copper tubing on an aluminum plate under iron-tempered glass as costlier but better in cold weather. Unglazed rubber collectors are the low-cost warm-weather type. A hose loop is not a DOE collector type. A drum is not a pool collector.DOE Energy Saver, Solar Swimming Pool Heaters
Replacing a conventional pool heater with solar may call for what, according to DOE?
- a.A smaller filter, with the same pump
- b.No pump at all; solar heating is passive
- c.A larger pump, or a separate smaller one✓
- d.A second sand filter on the return line
DOE says solar may need a pump larger than the current one, or a separate smaller pump to move water through the collectors. A smaller filter does not move water to the roof. Collectors need pumped flow. A second filter does not address pumping.DOE Energy Saver, Solar Swimming Pool Heaters
When can unglazed collectors serve an indoor pool in a cold climate?
- a.If antifreeze circulates through the pool
- b.If the collectors face north at a steep tilt
- c.If it is designed to drain back to the pool✓
- d.If the collectors are painted white on top
DOE says unglazed collectors can serve indoor pools in cold climates if the system drains back to the pool when idle. White paint would reduce absorption and does not stop freezing. A north orientation reduces heat and does not prevent freezing. Antifreeze in pool water is not a design option.DOE Energy Saver, Solar Swimming Pool Heaters
DOE reports a typical installed cost of $2,500 to $4,000 for a solar pool heater. What payback does it give?
- a.8 to 12 years
- b.1 to 7 years✓
- c.15 to 20 years
- d.Under 3 months
DOE gives a payback of between 1 and 7 years for a solar pool heating system. 15 to 20 years is far longer than DOE reports. 8 to 12 years is longer than DOE reports. Under 3 months is far shorter than DOE reports.DOE Energy Saver, Solar Swimming Pool Heaters