CCP CCP Plumbing & Mechanical Systems 1 — Questions and Answers
Question 1: During commissioning of a domestic hot water (DHW) system, what minimum temperature must storage water be maintained at to prevent Legionella growth per ASHRAE 188?
- 100°F (38°C)
- 120°F (49°C)
- 140°F (60°C) (Correct answer)
- 160°F (71°C)
Correct answer: 140°F (60°C)
ASHRAE 188 requires domestic hot water storage at or above 140°F (60°C) to prevent Legionella bacteria proliferation, a critical public health concern verified during commissioning.
Question 2: What is the primary purpose of commissioning a domestic water pressure-reducing valve (PRV)?
- To increase water pressure for upper floors
- To confirm the PRV maintains downstream pressure within the design range under varying flow conditions (Correct answer)
- To test backflow preventer operation
- To verify water meter accuracy
Correct answer: To confirm the PRV maintains downstream pressure within the design range under varying flow conditions
A PRV commissioning check confirms the valve modulates correctly to maintain design downstream pressure (typically 60–80 psi) under both low-flow and high-flow conditions.
Question 3: A commissioning agent is verifying a hydronic heating system. What does 'delta-T' refer to, and why is it significant?
- The temperature difference between supply and return water, indicating heat transfer efficiency (Correct answer)
- The pressure drop across the heat exchanger
- The difference between indoor and outdoor temperatures
- The temperature rise across the boiler heat exchanger only
Correct answer: The temperature difference between supply and return water, indicating heat transfer efficiency
Delta-T is the temperature difference between supply and return water in a hydronic loop; a low delta-T indicates poor heat transfer or excessive flow, reducing system efficiency and capacity.
Question 4: What is the purpose of a backflow preventer, and what commissioning test confirms its function?
- It increases water pressure; tested by flow measurement
- It prevents contaminated water from flowing back into the potable supply; tested by a certified backflow preventer test (Correct answer)
- It filters sediment from domestic water; tested by pressure drop measurement
- It regulates hot water temperature; tested by thermostat calibration
Correct answer: It prevents contaminated water from flowing back into the potable supply; tested by a certified backflow preventer test
A backflow preventer protects the potable water supply from contamination; commissioning requires a certified tester to perform a differential pressure test per local code requirements.
Question 5: During commissioning of a chilled water system, why is air purging of the hydronic loop critical?
- Air purging improves the chemical treatment effectiveness
- Trapped air causes pump cavitation, reduced flow, noise, and poor heat transfer in hydronic coils (Correct answer)
- Air purging is required only for steam systems
- Air must be added to maintain system pressure
Correct answer: Trapped air causes pump cavitation, reduced flow, noise, and poor heat transfer in hydronic coils
Air trapped in hydronic systems causes pump cavitation, reduces flow capacity, creates noise, and degrades coil heat transfer performance, all of which must be eliminated before functional testing.
Question 6: What is the purpose of chemical water treatment in a cooling tower system, and how is it verified during commissioning?
- To increase cooling tower efficiency by adding surfactants, verified by flow testing
- To control scale, corrosion, and biological growth; verified by reviewing the water treatment program and testing water chemistry (Correct answer)
- To reduce water consumption, verified by metering
- To improve condenser water temperature, verified by thermometer readings
Correct answer: To control scale, corrosion, and biological growth; verified by reviewing the water treatment program and testing water chemistry
Chemical treatment controls scale, corrosion, and Legionella in cooling tower water; commissioning verifies that an approved water treatment program is in place and that initial water chemistry meets design parameters.
CCP CCP Plumbing & Mechanical Systems 1
During commissioning of a domestic hot water (DHW) system, what minimum temperature must storage water be maintained at to prevent Legionella growth per ASHRAE 188?