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100+ Free AZ ROC C-77 Plumbing Including Solar (Commercial) Practice Questions

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2026 Statistics

Key Facts: AZ ROC C-77 Plumbing Including Solar (Commercial) Exam

100 Questions

Official Question Count

PSI Candidate Information Bulletin

240 Minutes

Time Limit

PSI Candidate Information Bulletin

70%

Passing Score

Arizona Registrar of Contractors

$66

Exam Fee

PSI Services LLC

Open Book Computerized MCQ

Exam Format

PSI / AZ ROC Guidelines

100 Questions

Practice Question Bank

OpenExamPrep Practice Bank

The Arizona ROC C-77/CR-77 Commercial Plumbing Including Solar Examination consists of 100 multiple-choice questions administered in a 240-minute open-book PSI session, plus a separate 30-question / 75-minute solar examination with a 70% passing requirement ($66 exam fee). This practice question bank provides 100 realistic practice questions grounded in 2026 codes with detailed step-by-step calculations and technical explanations.

Sample AZ ROC C-77 Plumbing Including Solar (Commercial) Practice Questions

Try these sample questions to test your AZ ROC C-77 Plumbing Including Solar (Commercial) exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1In an active solar water heating system, what is the primary operational function of a differential temperature controller?
A.To energize the circulator pump when collector temperature exceeds storage tank temperature by a set differential (Delta T ON)
B.To modulate the flow rate of city water directly into the solar collectors based on outdoor ambient air temperature
C.To switch the auxiliary backup heater on whenever solar storage tank temperature drops below 160°F
D.To open the thermal expansion valve when collector loop pressure reaches 100 psi
Explanation: A differential temperature controller monitors sensors located at the solar collector outlet and the bottom of the solar storage tank. It starts the circulating pump when the collector temperature is higher than the tank temperature by a designated threshold (typically 8°F to 12°F Delta T ON), maximizing heat collection efficiency.
2Which piping design rule is critical for proper operation of an active drainback solar thermal water heating system?
A.All solar loop piping above the drainback tank must slope downward continuously toward the tank at a minimum of 1/4 inch per foot with zero traps or dips
B.Collector return piping must be trapped below roof line to maintain a permanent liquid seal at all times
C.Solar collectors must be installed perfectly level with horizontal supply lines to prevent air pockets
D.Drainback lines must be sized one pipe size smaller than supply lines to create backpressure during shutdown
Explanation: Drainback systems protect collectors from freezing and overheating by allowing fluid to drain by gravity into an indoor drainback reservoir whenever the pump stops. All piping and collectors must maintain a continuous slope of at least 1/4 inch per foot toward the reservoir, with no sagging or trapped sections where fluid could linger and freeze.
3Under the International Solar Energy Code (ISPC) and Uniform Plumbing Code (UPC), which heat transfer fluid is classified as non-toxic and permitted in single-wall heat exchangers connected to potable water?
A.USP grade propylene glycol / water solution
B.Industrial ethylene glycol antifreeze solution
C.Mineral oil heat transfer fluid
D.Aromatic hydrocarbon heat exchange liquid
Explanation: USP food-grade propylene glycol is classified as a non-toxic (Category 1) fluid under plumbing and solar codes. It is acceptable for use in single-wall heat exchangers separating the collector loop from domestic potable water systems, whereas toxic fluids like ethylene glycol mandate double-wall heat exchangers with atmospheric leak paths.
4A closed-loop commercial solar thermal system contains a total fluid volume of 40 gallons of a 40% propylene glycol mix. The fluid expands by 5% when heated from 60°F to its maximum operating temperature. What minimum acceptance volume must the diaphragm expansion tank provide to absorb fluid thermal expansion?
A.2.0 gallons
B.4.0 gallons
C.6.0 gallons
D.8.0 gallons
Explanation: The fluid expansion volume V_exp is calculated as total fluid volume multiplied by the volumetric expansion fraction: V_exp = 40 gallons × 0.05 = 2.0 gallons. The expansion tank acceptance volume must be at least equal to this expansion volume to prevent system overpressurization.
5What design feature is mandated by code for a double-wall heat exchanger used between a solar loop carrying toxic fluid and a domestic potable water system?
A.An open atmospheric leak path between the two separation walls to visibly discharge fluid if either wall fails
B.A dual-check valve with intermediate atmospheric vent on the solar fluid supply line
C.An internal motorized shutoff valve wired to a conductivity sensor inside the potable water line
D.A secondary storage buffer tank placed between the primary collector loop and heat exchanger
Explanation: Code standards (IPC Chapter 6 and ISPC) require double-wall heat exchangers handling toxic transfer fluids to feature an intermediate space open to the atmosphere. If either the potable water wall or solar fluid wall fails, fluid will leak harmlessly to the outside, providing a visual warning without contaminating the drinking water.
6What does an SRCC OG-100 certification label on a solar thermal collector verify for commercial installations?
A.Independent laboratory thermal performance testing, structural durability, and standardized BTU output ratings
B.Automatic compliance with local Arizona building electrical and PV inverter codes
C.Exemption from local plumbing permit requirements and structural roof inspections
D.Guaranteed 25-year zero-maintenance warranty coverage backed by the EPA
Explanation: The Solar Rating & Certification Corporation (SRCC) OG-100 standard certifies individual solar thermal collectors based on independent thermal performance rating tests, pressure resistance, and structural integrity. OG-100 certification is required by building codes and rebate programs.
7To prevent erosion-corrosion in copper solar loop piping operating at temperatures exceeding 140°F, what is the maximum recommended fluid velocity?
A.5 feet per second
B.8 feet per second
C.10 feet per second
D.12 feet per second
Explanation: The Copper Development Association (CDA) and plumbing engineering standards recommend limiting flow velocity in copper tubing to 5 feet per second (fps) for hot water systems above 140°F (such as solar thermal collector loops). Higher velocities accelerate erosion-corrosion, especially at fittings and elbows.
8For optimal year-round domestic hot water production in Phoenix, Arizona (latitude approximately 33.5°N), at what tilt angle from horizontal should fixed solar thermal collectors be mounted?
A.33° to 35° facing due South
B.15° to 18° facing due East
C.50° to 55° facing due West
D.0° (flat horizontal) facing North
Explanation: For year-round solar thermal domestic water heating, collectors should be tilted at an angle roughly equal to the local latitude (33.5° for Phoenix, rounded to 33°-35°) and oriented toward true South (180° azimuth) to equalize summer and winter solar radiation absorption.
9What condition occurs in a closed solar collector loop when pump failure or power loss coincides with full solar radiation, causing fluid temperature to reach boiling point?
A.Thermal stagnation
B.Laminar cavitating
C.Thermosyphon backfeed
D.Hydraulic implosion
Explanation: Thermal stagnation occurs when no fluid flows through solar collectors exposed to intense sunlight. Absorber temperatures can reach 300°F to 400°F in flat-plate collectors, vaporizing heat transfer fluid and generating high steam pressure that must be accommodated by expansion tanks and relief valves.
10Why are evacuated tube solar collectors preferred over unglazed collectors for high-temperature commercial water heating applications?
A.The vacuum between inner and outer glass tubes virtually eliminates conductive and convective heat losses
B.Evacuated tubes generate direct current electricity to power internal circulation pumps without external power
C.Evacuated tubes require zero freeze protection and can operate filled with pure water down to -40°F
D.Unglazed collectors reflect more than 90% of incident sunlight at fluid temperatures above 100°F
Explanation: Evacuated tube collectors utilize a sealed vacuum envelope surrounding the absorber element. Because a vacuum contains no air molecules, conductive and convective heat loss from the hot absorber to cold ambient air is almost completely eliminated, maintaining high efficiency at elevated delivery temperatures (160°F–200°F).

About the AZ ROC C-77 Plumbing Including Solar (Commercial) Exam

The Arizona ROC C-77/CR-77 Plumbing Including Solar (Commercial) Examination is a 100-question, 240-minute open-book computer-administered trade exam managed by PSI Services LLC for the Arizona Registrar of Contractors. It evaluates comprehensive technical knowledge across solar thermal collector arrays, active/passive solar systems, glycol closed loops, heat exchangers, freeze and stagnation protection, differential temperature controls, DWV pipe sizing, water supply WSFU calculations, backflow protection for toxic solar loops (RPZ), storm drainage roof drains, commercial water heaters, fuel gas pipe sizing under IFGC/NFPA 54, ADEQ septic standards, hydronics, and OSHA excavation safety.

Assessment

Two separately scored PSI examinations, both open book and both requiring 70%: the main trade examination (100 questions / 240 minutes) and the solar examination (30 questions / 75 minutes). Solar content outline: Pumps and Storage Systems (6), Open and Closed Loop Systems (5), Pipes and Materials (5), System Designs (5), Collectors (3), Controls (3), Estimating and Sizing (2), Pool Systems (1).

Time Limit

240 minutes

Passing Score

70%

Exam Fee

$66 (Arizona ROC / PSI Services LLC)

AZ ROC C-77 Plumbing Including Solar (Commercial) Exam Content Outline

15%

Drainage Waste and Vents

15 of 100 items on the official PSI content outline. DWV sizing, fixture units, vent types, slopes and cleanouts.

12%

Water Supply Systems

12 of 100 items on the official PSI content outline. Sizing, materials, pressure, water hammer and distribution layout.

10%

Fuel Gas

10 of 100 items on the official PSI content outline. Gas pipe sizing, materials, appliance connections and testing.

10%

Septic and Sewer

10 of 100 items on the official PSI content outline. Building sewers, septic tanks and leaching lines within property lines.

8%

General Knowledge and General Regulations

8 of 100 items on the official PSI content outline. Scope of work, permits, general code administration and trade practice.

6%

Plumbing Fixtures (including water heaters and accessibility)

6 of 100 items on the official PSI content outline. Fixture setting, water heaters, relief valves and accessible fixture requirements.

5%

Backflow Prevention

5 of 100 items on the official PSI content outline. Assembly selection, air gaps, cross-connection control and testing.

5%

Roof Drains and Storm Drainage Systems

5 of 100 items on the official PSI content outline. Primary and secondary roof drainage, sizing and overflow.

5%

Specialty Plumbing, Interceptors, and Traps

5 of 100 items on the official PSI content outline. Grease and oil interceptors, special wastes and trap seals.

5%

Isometric Analysis

5 of 100 items on the official PSI content outline. Reading and interpreting isometric plumbing drawings.

5%

Hydronics

5 of 100 items on the official PSI content outline. Hot water heating and supply systems within the classification's pressure and temperature limits.

5%

Fire Sprinklers

5 of 100 items on the official PSI content outline. NFPA 13, 13D and 13R residential and light-hazard sprinkler basics.

5%

Excavation

5 of 100 items on the official PSI content outline. Trenching, bedding, backfill and excavation safety for underground piping.

4%

Indirect Waste

4 of 100 items on the official PSI content outline. Indirect waste receptors, air gaps and air breaks.

How to Pass the AZ ROC C-77 Plumbing Including Solar (Commercial) Exam

What You Need to Know

  • Passing score: 70%
  • Assessment: Two separately scored PSI examinations, both open book and both requiring 70%: the main trade examination (100 questions / 240 minutes) and the solar examination (30 questions / 75 minutes). Solar content outline: Pumps and Storage Systems (6), Open and Closed Loop Systems (5), Pipes and Materials (5), System Designs (5), Collectors (3), Controls (3), Estimating and Sizing (2), Pool Systems (1).
  • Time limit: 240 minutes
  • Exam fee: $66

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

AZ ROC C-77 Plumbing Including Solar (Commercial) Study Tips from Top Performers

1Master solar thermal system fundamentals: differential controller operation, heat exchanger requirements (double-wall vs single-wall for toxic fluids), glycol freeze protection, and drainback system pitch rules.
2Practice solar collector installation requirements under ISPC/USEC and IBC: tilt angles for Arizona latitude (~33°-35°), roof lag screw embedment into structural rafters, and flashing details.
3Study backflow prevention rules for solar systems: Reduced Pressure Zone (RPZ) assemblies are mandated whenever toxic chemicals or non-food-grade heat transfer fluids are used.
4Review IPC/UPC Drainage Fixture Unit (DFU) and Water Supply Fixture Unit (WSFU) sizing tables for commercial building drains, stacks, water distribution mains, and flushometer valves.
5Memorize OSHA 29 CFR 1926 Subpart P trench safety standards: depth threshold for protective systems (5 ft), maximum ladder travel distance (25 ft), spoil pile setback (2 ft), and Arizona 811 notice period.

Frequently Asked Questions

How many questions are on the official Arizona ROC C-77/CR-77 Plumbing Including Solar exam?

The official PSI Arizona ROC C-77/CR-77 Commercial Plumbing Including Solar examination contains 100 questions with 240 minutes allowed, and the 'Including Solar' classification adds a separate C-77 Solar examination of 30 questions with 75 minutes allowed.

What passing score is required for the AZ ROC C-77 exam?

A minimum passing score of 70% is required on each examination: 70 correct out of 100 on the trade portion and 21 correct out of 30 on the solar portion.

Is the Arizona ROC C-77 Commercial Plumbing Including Solar exam open book?

Yes, the examination is open-book. Approved reference materials—such as the International Plumbing Code, Uniform Solar Energy Code / International Solar Energy Code, International Fuel Gas Code / NFPA 54, and OSHA 29 CFR 1926—may be brought into the PSI testing center.

What key difference exists between the C-37 Plumbing exam and the C-77 Plumbing Including Solar exam?

The C-77/CR-77 license adds comprehensive coverage of solar thermal water heating systems (active/passive collectors, heat transfer fluids, solar heat exchangers, differential controllers, freeze/overheat protection, and solar loop hydronics) in addition to full commercial plumbing.

Where can I schedule the AZ ROC C-77/CR-77 examination?

Examinations are scheduled online through PSI Services LLC at https://test-takers.psiexams.com/azcon or by calling PSI candidate services.