MECHANICAL AND ELECTRICAL SYSTEMS MIDTERM EXAM 1 QUESTIONS AND ANSWERS |
EXAM PREP & STUDY GUIDE 2026/2027
What does a Building Energy Management System (BEMS) control? - ✔✔HVAC, lighting, fire,
safety, and security functions
What is Direct Digital Control (DDC)? - ✔✔A hierarchical system where a central control center
gathers input, makes decisions, and sends commands via network
What are the three main ways to control space temperature? - ✔✔1. Vary conditioned air
temperature, constant flow; 2. Vary conditioned air flow, constant temperature (most common);
3. Vary both temperature and flow (complex systems)
What is a VAV (Variable Air Volume) terminal box? - ✔✔A device that adjusts air flow to
maintain temperature, often decreasing flow under light load, which can cause stuffiness
What do diffusers, registers, and grilles do? - ✔✔They direct the flow of air into occupied
spaces
What is a Single-Zone CAV system? - ✔✔A constant air volume system serving one zone with
fixed airflow
What is a Multizone CAV system? - ✔✔A system that uses separate ducts for different zones,
allowing temperature control per zone
What is a Multiple-Zone VAV system? - ✔✔A system where airflow volume varies per zone to
maintain temperature
How do baseboard convectors counter downdrafts? - ✔✔By heating air at the perimeter wall
base so it rises and offsets cold air near windows
, Where should equipment with desirable heat (e.g., radiators) be placed? - ✔✔Inside the
building
Where should heat rejection equipment (chillers, cooling towers) be placed? - ✔✔Outside,
since they release unwanted heat
Why are rooftop units more costly to maintain? - ✔✔Difficult access, safety concerns,
weathering, and vibration issues
What purpose do screen walls serve? - ✔✔Improve aesthetics and mitigate noise, but add
structural and maintenance complexity
Why is water often used instead of air for cooling? - ✔✔Water has higher specific heat,
requiring less volume than air to dissipate heat
What risks do piping penetrations create? - ✔✔Potential leaks, especially with vertical roof
penetrations
What are the pros of central vs distributed HVAC systems? - ✔✔Central = more efficient but
larger losses in long ductwork/piping. Distributed = smaller units, less loss, but potentially less
efficient
What are the space tradeoffs of boilers vs district steam? - ✔✔Boilers require more space
(sometimes even a separate building), while district steam reduces equipment footprint
Why must fan rooms be designed with clearances? - ✔✔To allow maintenance access and
ductwork routing
EXAM PREP & STUDY GUIDE 2026/2027
What does a Building Energy Management System (BEMS) control? - ✔✔HVAC, lighting, fire,
safety, and security functions
What is Direct Digital Control (DDC)? - ✔✔A hierarchical system where a central control center
gathers input, makes decisions, and sends commands via network
What are the three main ways to control space temperature? - ✔✔1. Vary conditioned air
temperature, constant flow; 2. Vary conditioned air flow, constant temperature (most common);
3. Vary both temperature and flow (complex systems)
What is a VAV (Variable Air Volume) terminal box? - ✔✔A device that adjusts air flow to
maintain temperature, often decreasing flow under light load, which can cause stuffiness
What do diffusers, registers, and grilles do? - ✔✔They direct the flow of air into occupied
spaces
What is a Single-Zone CAV system? - ✔✔A constant air volume system serving one zone with
fixed airflow
What is a Multizone CAV system? - ✔✔A system that uses separate ducts for different zones,
allowing temperature control per zone
What is a Multiple-Zone VAV system? - ✔✔A system where airflow volume varies per zone to
maintain temperature
How do baseboard convectors counter downdrafts? - ✔✔By heating air at the perimeter wall
base so it rises and offsets cold air near windows
, Where should equipment with desirable heat (e.g., radiators) be placed? - ✔✔Inside the
building
Where should heat rejection equipment (chillers, cooling towers) be placed? - ✔✔Outside,
since they release unwanted heat
Why are rooftop units more costly to maintain? - ✔✔Difficult access, safety concerns,
weathering, and vibration issues
What purpose do screen walls serve? - ✔✔Improve aesthetics and mitigate noise, but add
structural and maintenance complexity
Why is water often used instead of air for cooling? - ✔✔Water has higher specific heat,
requiring less volume than air to dissipate heat
What risks do piping penetrations create? - ✔✔Potential leaks, especially with vertical roof
penetrations
What are the pros of central vs distributed HVAC systems? - ✔✔Central = more efficient but
larger losses in long ductwork/piping. Distributed = smaller units, less loss, but potentially less
efficient
What are the space tradeoffs of boilers vs district steam? - ✔✔Boilers require more space
(sometimes even a separate building), while district steam reduces equipment footprint
Why must fan rooms be designed with clearances? - ✔✔To allow maintenance access and
ductwork routing
