System Design Flashcards

Which factor does NOT directly affect the heat loss calculation through a wall assembly?

Answer: Color of the interior paint

Heat loss Q = U × A × ΔT; interior paint color has no significant effect on conductive heat loss through a wall.

In a constant-air-volume (CAV) system, how is zone temperature control typically achieved?

Answer: Using a reheat coil in the zone terminal

CAV systems maintain constant airflow and use zone reheat coils to raise supply air temperature as needed for individual zone temperature control.

What is 'static pressure' in duct system design?

Answer: The pressure acting perpendicular to airflow on duct walls

Static pressure is the pressure exerted outward on duct walls perpendicular to the direction of airflow, driving air through the distribution system.

A two-pipe changeover hydronic system limitation is that it:

Answer: Cannot provide heating and cooling to different zones at the same time

Two-pipe changeover systems use the same piping for either hot or chilled water, so all zones must be in heating or cooling mode simultaneously.

What is the purpose of a bypass duct or 'dump zone' in a zoned forced-air system?

Answer: Relieve excess system pressure when zone dampers close

A bypass duct diverts excess supply air back to the return plenum when multiple zone dampers close, preventing excessive static pressure on the blower.

According to ASHRAE 62.2, residential ventilation rates are based primarily on:

Answer: Floor area and number of bedrooms

ASHRAE 62.2 calculates required ventilation airflow using a formula that accounts for conditioned floor area and the number of bedrooms as a proxy for occupant count.

In HVAC design, 'face velocity' refers to:

Answer: Airflow velocity across the face area of a coil or filter

Face velocity is the air speed across the frontal area of a cooling coil, heating coil, or filter, measured in feet per minute (FPM).