Systems & Equipment Performance Flashcards
7 cards from real CCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Systems & Equipment Performance flashcards as text
A rooftop unit (RTU) is short-cycling on the high-pressure cutout during commissioning. Which cause should be investigated FIRST?
Answer: Insufficient condenser airflow due to dirty coil or fan failure
Insufficient condenser airflow is the most common cause of high discharge pressure trips and should be verified before investigating refrigerant circuit issues.
What does superheat measurement at a refrigerant expansion valve indicate?
Answer: How much the refrigerant vapor exceeds saturation temperature at that pressure
Superheat is the temperature of refrigerant vapor above its saturation temperature at a given pressure, confirming all refrigerant has evaporated before the compressor.
In a variable flow hydronic system, what is the minimum recommended differential pressure setpoint strategy for energy optimization?
Answer: Differential pressure reset based on the most open valve position
Resetting differential pressure setpoint based on the most open control valve minimizes pump energy while ensuring adequate pressure for all loads.
During commissioning of a DDC-controlled air handling unit, the mixed air temperature is consistently lower than calculated. This MOST LIKELY indicates:
Answer: Outside air damper leaking when commanded closed
An outside air damper leaking when commanded closed allows cold outdoor air to infiltrate, reducing mixed air temperature below the designed minimum.
The net positive suction head available (NPSHa) must exceed NPSHr to prevent:
Answer: Cavitation and associated pump damage
NPSHa must exceed NPSHr to prevent cavitation, which occurs when fluid pressure drops below vapor pressure, forming destructive vapor bubbles in the impeller.
Which of the following BEST describes the purpose of economizer lockout controls in a chiller plant?
Answer: To disable waterside or airside free cooling when conditions make it inefficient
Economizer lockout controls disable free cooling modes when ambient conditions (wet-bulb or dry-bulb) make mechanical cooling more efficient than economizing.
A laboratory fume hood's face velocity reads above design during commissioning. The MOST appropriate corrective action is to:
Answer: Reduce exhaust flow at the hood or increase supply air
Reducing exhaust airflow at the hood or increasing supply air to maintain proper face velocity within design range is the standard TAB correction method.