Arizona ROC C-78/CR-78 Solar Plumbing, Liquid Systems Only Examination

What is the recommended fixed tilt angle for flat-plate solar thermal collectors installed in Phoenix, Arizona (approximate latitude 33.4° N) to optimize year-round domestic hot water performance?

• A15 degrees (Latitude minus 18 degrees)
• B33 degrees (Equal to local latitude)
• C48 degrees (Latitude plus 15 degrees)
• D60 degrees (Latitude plus 27 degrees)

To optimize a liquid solar thermal system specifically for winter performance in Arizona, what rule of thumb is applied to adjust the collector tilt angle relative to local latitude?

• ASubtract 15 degrees from local latitude
• BAdd 15 degrees to local latitude
• CMultiply local latitude by 0.5
• DSet tilt angle to 90 degrees vertical

In the Northern Hemisphere, toward which true compass direction should fixed solar thermal collectors be oriented to capture maximum daily solar radiation?

• ATrue East (90 degrees azimuth)
• BTrue West (270 degrees azimuth)
• CTrue South (180 degrees azimuth)
• DMagnetic North (0 degrees azimuth)

When aligning solar collectors in Phoenix, Arizona using a magnetic compass, an installer must account for an approximate magnetic declination of 9° East. What compass reading corresponds to True South (180° true)?

• A171 degrees magnetic
• B189 degrees magnetic
• C180 degrees magnetic
• D195 degrees magnetic

Which optical properties characterize a high-performance selective surface coating on a flat-plate solar collector absorber?

• ALow solar absorptance (α ≤ 0.20) and high thermal emittance (ε ≥ 0.90)
• BHigh solar absorptance (α ≥ 0.95) and low thermal emittance (ε ≤ 0.10)
• CHigh solar absorptance (α ≥ 0.95) and high thermal emittance (ε ≥ 0.90)
• DLow solar absorptance (α ≤ 0.20) and low thermal emittance (ε ≤ 0.10)

In a heat-pipe evacuated tube collector array, how is heat transferred from the individual glass evacuated tubes to the solar fluid loop?

• ASolar loop fluid circulates directly inside each glass tube through plastic dip tubes
• BVapor inside the copper heat pipe rises to a condenser bulb inserted into a dry manifold…
• CEvacuated tubes use air pumps to blow heated air across an external heat exchanger coil
• DLiquid refrigerant flows down an open gutter into the domestic water storage tank

According to standard roofing and building structural practices for solar thermal mounting, lag bolts securing mounting brackets into wood rafters must penetrate into the solid wood structural rafter by at least what minimum depth?

• A0.5 inches (13 mm)
• B1.0 inch (25 mm)
• C2.0 inches (51 mm)
• D4.5 inches (114 mm)

A solar water heating system consists of four 4' x 10' flat-plate collectors installed in parallel. If each collector requires a manufacturer-specified flow rate of 0.75 GPM, what is the required total flow rate for the collector array?

• A0.75 GPM
• B1.50 GPM
• C3.00 GPM
• D6.00 GPM

Why is reverse-return piping preferred over direct-return piping in multi-collector solar thermal arrays?

• AIt reduces total piping material length by 50 percent
• BIt ensures equal pipe path length and equal fluid resistance through every collector
• CIt allows domestic potable water to mix directly with toxic glycol loop fluid
• DIt eliminates the requirement for an expansion tank in closed loops

When penetrating a shingle roof to install solar collector mounting standoffs, what is the proper method to ensure a long-term watertight seal per building codes?

• AApply silicone sealant over top of the shingle surface after tightening the bolt
• BInstall approved metal flashing slid beneath the upslope shingle course and sealed around…
• CWrap lag screws in duct tape prior to driving them into roof sheathing
• DFill the rafter space below the penetration with expanding spray foam insulation

To prevent inter-row shading between parallel rows of flat-plate collectors on a flat roof, spacing between rows is calculated based on solar position at solar noon on which date?

• ASummer Solstice (June 21)
• BVernal Equinox (March 21)
• CWinter Solstice (December 21)
• DAutumnal Equinox (September 21)

A solar thermal liquid collector system is designed exclusively for seasonal swimming pool heating from late spring through early autumn in Arizona. What collector tilt angle is most appropriate?

• ALatitude minus 10 to 15 degrees (approx. 18 to 23 degrees)
• BLatitude plus 15 degrees (approx. 48 degrees)
• CLatitude plus 30 degrees (approx. 63 degrees)
• DVertical 90 degrees wall mount

What physical condition occurs in a liquid solar thermal collector during stagnation?

• AFluid pump speeds increase uncontrollably due to high voltage generated by heat
• BSolar radiation continues to strike the collector while fluid circulation has stopped, ca…
• CCollector fluid freezes instantly due to sudden pressure drops in the manifold
• DVacuum seals in evacuated tubes automatically vent non-potable steam into ambient air

High-efficiency flat-plate solar collectors with selective absorber surfaces can reach maximum stagnation temperatures of approximately what range under full desert sun?

• A140°F to 160°F (60°C to 71°C)
• B180°F to 200°F (82°C to 93°C)
• C350°F to 400°F (177°C to 204°C)
• D650°F to 800°F (343°C to 427°C)

When evaluating structural load on a roof for a liquid solar thermal installation, what classification is given to the permanent weight of the filled collectors, mounting frames, and fluid-filled piping?

• ALive load
• BDead load
• CEnvironmental uplift load
• DDynamic impact load

Why is low-iron tempered glass specified for flat-plate solar collector glazing rather than standard float window glass?

• ALow-iron tempered glass has high solar transmittance (90%+), high strength, and high resi…
• BLow-iron glass blocks all shortwave solar radiation from entering the collector
• CStandard float glass is too expensive to manufacture in rectangular dimensions
• DLow-iron glass absorbs all infrared energy directly into the glass pane

Where MUST an air elimination vent or air bottle be installed in a closed-loop pressurized liquid solar thermal collector array?

• AAt the lowest point of the system near the expansion tank outlet
• BAt the highest point of the collector array where fluid leaves the collectors
• CDirectly between the pump suction port and check valve
• DInside the storage tank dip tube connection

A solar thermal array consists of two flat-plate collectors, each having an absorber area of 32 sq. ft. On a clear day in Arizona, average solar radiation striking the array is 2,000 BTU/sq. ft/day. If the array operates at an overall thermal efficiency of 50%, how much heat energy is delivered to the storage tank in one day?

• A32,000 BTU
• B64,000 BTU
• C128,000 BTU
• D256,000 BTU

Which heat transfer fluid is approved by the International Plumbing Code (IPC) and Uniform Solar Energy Code (USEC) for use in indirect solar domestic water heating systems with single-wall heat exchangers?

• AAutomotive ethylene glycol anti-freeze
• BFood-grade USP Propylene Glycol with non-toxic inhibitors
• CMineral oil with aromatic hydrocarbon solvents
• DIndustrial chlorinated heat transfer fluid

How does a solar thermal drainback system protect collector array piping from freezing during cold winter nights?

• AIt circulates electric heating cable current through the solar copper pipes
• BWhen the pump turns off, all fluid in outdoor collectors drains by gravity into an indoor…
• CIt injects high-pressure nitrogen gas into collectors to displace liquid water
• DIt maintains a continuous high-velocity flow of distilled water through collectors 24 hou…

What is the minimum required continuous pitch (slope) for horizontal solar loop piping in a drainback system to guarantee complete gravity drainage?

• A1/16 inch per foot of horizontal run
• B1/8 inch per foot of horizontal run
• C1/4 inch per foot of horizontal run
• D1.0 inch per foot of horizontal run

Which hydronic component is mandatory in a closed-loop pressurized glycol solar system but is NOT required for fluid thermal expansion in an atmospheric drainback system?

• ACirculator pump
• BDiaphragm expansion tank
• CSolar collector absorber plate
• DStorage tank heat exchanger

What specialized service tool should a solar plumbing technician use to accurately measure the freeze protection level and concentration percentage of a propylene glycol heat transfer fluid?

• AStandard hydrometer calibrated for automotive ethylene glycol
• BOptical refractometer with propylene glycol scale
• CDigital pH meter with glass electrode
• DBourdon tube pressure gauge

During maintenance of a closed glycol solar system, testing fluid with pH test strips reveals a pH reading of 6.2. What does this indicate and what corrective action is required?

• AFluid is in ideal condition; no action required
• BGlycol has oxidized and become acidic; system must be flushed, purged, and refilled with…
• CGlycol concentration is too high; add 10 gallons of pure ethylene glycol immediately
• DSystem pressure is too high; vent air from the expansion tank valve

What is the primary operational risk associated with using active recirculation freeze protection in direct water solar thermal systems?

• AExcessive storage tank temperatures during freezing weather
• BComplete freeze protection failure and catastrophic pipe bursting during electrical power…
• CRapid accumulation of glycol sludge inside domestic hot water faucets
• DHigh vacuum pressure collapsing the water storage tank

How does the volumetric thermal expansion rate of a 50/50 propylene glycol/water mixture compare to pure water over the same temperature rise from 40°F to 180°F?

• APropylene glycol solution expands significantly more than pure water
• BPropylene glycol solution expands at less than half the rate of pure water
• CPropylene glycol solution experiences zero expansion when heated
• DPropylene glycol solution shrinks in volume as temperature rises

How do mechanical freeze-protection valves (dribble valves) installed on outdoor direct solar piping function when ambient temperatures approach freezing?

• AThey electrically energize a solenoid coil to seal the system under 100 psi pressure
• BThey mechanically open near 35°F to 40°F, discharging cold water to allow warmer supply w…
• CThey isolate collectors by closing internal ball valves to trap stagnant air
• DThey inject anti-freeze chemicals into the municipal water main

A closed-loop solar system has a total fluid capacity of 16 gallons. To achieve freeze protection down to -20°F (-29°C), manufacturer tables require a 50% propylene glycol by volume concentration. How many gallons of pure propylene glycol and distilled water are required?

• A4 gallons glycol and 12 gallons water
• B8 gallons glycol and 8 gallons water
• C12 gallons glycol and 4 gallons water
• D16 gallons glycol and 0 gallons water

A pressurized solar collector array is located on a roof 30 feet above the basement expansion tank and pump station. To prevent vapor locking and boiling at the array top, what minimum cold static fill pressure should be maintained at the basement gauge?

• A5 psi
• B13 psi
• C23 psi
• D60 psi

Under the Uniform Solar Energy Code (USEC) fluid hazard classification, food-grade USP propylene glycol with non-toxic additives falls into which fluid safety category?

• ACategory 1 / Class I (Non-toxic / Food grade)
• BCategory 4 / High Hazard Toxicity
• CFlammable Class IA Liquid
• DRadioactive / Corrosive Waste

In a drainback solar liquid system, where is the atmospheric air vent/vacuum breaker port situated within the closed drainback loop?

• AAt the bottom of the water heater cold inlet dip tube
• BAbove the static water line inside the unpressurized drainback reservoir tank or high-poi…
• CDirectly downstream of the pressure relief valve discharge pipe
• DInside the main municipal water meter box

What operational problem occurs when hard unconditioned water is circulated through direct solar thermal collectors in areas like Arizona with high total dissolved solids (TDS)?

• ACopper absorber pipes dissolve rapidly due to acid formation
• BCalcium carbonate scale precipitates on hot copper tube walls, reducing heat transfer and…
• CWater turns into flammable hydrogen gas at 120°F
• DWater density increases, causing pump motors to burn out from overload

Why must uninhibited technical-grade propylene glycol NEVER be used in solar thermal collector loops?

• AUninhibited glycol rapidly oxidizes under heat and air exposure, forming organic acids th…
• BUninhibited glycol evaporates completely at room temperature
• CUninhibited glycol expands by 300 percent when cooled below freezing
• DUninhibited glycol causes solar collectors to absorb negative thermal radiation

To prevent erosion-corrosion in copper solar loop piping carrying hot glycol/water solutions above 140°F, what maximum fluid velocity should not be exceeded per Copper Development Association (CDA) standards?

• A2 feet per second (0.6 m/s)
• B5 feet per second (1.5 m/s)
• C12 feet per second (3.7 m/s)
• D25 feet per second (7.6 m/s)

How does the specific heat capacity of a 50/50 propylene glycol/water mixture compare to that of pure liquid water?

• APure water has a higher specific heat capacity (~1.0 BTU/lb·°F) than 50/50 glycol (~0.85…
• B50/50 glycol has double the specific heat capacity of pure water
• CBoth fluids have identical specific heat capacity values at all temperatures
• DPropylene glycol has zero heat capacity

What equipment and procedure are required to purge air and charge fluid into a closed-loop pressurized solar thermal system?

• AGravity funnel poured into the highest collector air vent
• BHigh-head fluid charging pump cart connected to fill/purge valves, circulating fluid in a…
• CBrazing torch applied to expansion tank inlet to draw fluid by thermal vacuum
• DCompressed air line pressurizing fluid from an open bucket into the drain line

Under International Plumbing Code (IPC) Section 608.16.3, what construction feature is mandatory for heat exchangers that utilize non-potable toxic heat transfer fluids to heat potable water?

• ASingle-wall copper coil with high-temperature epoxy coating
• BDouble-wall construction with an intermediate leak path vented to the atmosphere
• CTriple-wall cast iron shell with closed drain plugs
• DDirect submerged electric heating element barrier

When does the International Plumbing Code (IPC) permit the use of a SINGLE-WALL heat exchanger in a solar domestic water heating system?

• AOnly when the system operating pressure exceeds 300 psi
• BWhen the transfer fluid is potable water or classified as non-toxic (USP food-grade) AND…
• CWhenever the solar storage tank capacity is under 30 gallons
• DSingle-wall heat exchangers are strictly prohibited under all plumbing codes regardless o…

In a solar storage tank featuring an internal submerged heat exchanger coil, why is the coil located in the bottom third of the tank?

• ATo prevent the coil from coming into contact with incoming cold city water
• BBecause cold water settles at the tank bottom, maximizing heat transfer temperature diffe…
• CTo make coil replacement easier from the lower tank drain valve
• DBecause solar fluid naturally sinks to the bottom of the coil

What physical property of water enables thermal stratification inside a solar domestic hot water storage tank?

• AHot water is denser than cold water and settles at the bottom
• BWarm water is less dense than cold water, causing warmer water to naturally float to the…
• CWater viscosity increases dramatically at high temperatures, preventing fluid movement
• DWater molecules expand and lock into rigid crystalline structures above 140°F

In a two-tank solar domestic hot water installation, how are the solar storage pre-heat tank and the conventional backup water heater connected in relation to domestic water flow?

• AIn parallel, with cold water splitting equally to feed both tanks simultaneously
• BIn series, with cold city water feeding the solar pre-heat tank, whose outlet feeds the c…
• CIn series, with hot outlet of the backup heater feeding into the bottom of the solar stor…
• DIn a closed loop where domestic water recirculates continuously between tanks without fix…

Why must an ASSE 1017 certified thermostatic mixing valve be installed on the hot water outlet of a solar domestic storage tank?

• ATo prevent toxic glycol from entering the solar storage tank
• BSolar storage tanks can reach scalding temperatures (over 160°F); the valve blends cold w…
• CTo boost solar loop circulation pump pressure during peak sun hours
• DTo drain excess solar hot water onto the roof when tank reaches capacity

A closed solar collector loop contains 20 gallons of fluid. Thermal expansion over the maximum temperature range increases fluid volume by 1.2 gallons. If initial fill pressure is 30 psig and maximum allowable pressure relief setting is 60 psig, what is the minimum required acceptance volume of the diaphragm expansion tank?

• A0.6 gallons
• B1.2 gallons
• C3.6 gallons
• D20.0 gallons

Per ASME standards and International Plumbing Code (IPC), what are the standard factory pressure and temperature relief settings for a combination T&P relief valve installed on a solar domestic water storage tank?

• A50 psi and 140°F (60°C)
• B100 psi and 180°F (82°C)
• C150 psi and 210°F (99°C)
• D300 psi and 250°F (121°C)

In an external brazed plate heat exchanger, why are solar loop fluid and domestic water routed in a counter-flow configuration?

• ACounter-flow maintains the maximum temperature difference (mean temperature difference) b…
• BCounter-flow causes fluids to mix together to equalize hydraulic pressure
• CCounter-flow reduces liquid velocity to zero inside the plate channels
• DCounter-flow eliminates the need for circulating pumps on both sides

Before filling and pressurizing a closed-loop solar system with glycol, how should the diaphragm expansion tank air pre-charge pressure be set?

• ASet to 0 psi with Schrader valve stem removed
• BSet equal to the desired cold system fill static pressure while tank is unpressurized on…
• CSet to maximum relief valve rating (150 psi)
• DSet to 5 psi regardless of system height or design fill pressure