HVAC System Design 5

Question 1

In a VAV system, a minimum airflow setpoint for VAV terminal boxes is required primarily to:

Accepted Answer

Maintain adequate ventilation and thermal comfort at low cooling loads

Answer

Minimum airflow setpoints ensure each zone receives sufficient ventilation air and prevents 'dead air' conditions even when the cooling load is near zero.

Question 2

What is 'infiltration' as it applies to HVAC load calculations?

Accepted Answer

Uncontrolled air leakage into a building through cracks and gaps in the envelope

Answer

Infiltration is uncontrolled outdoor air that enters through gaps, cracks, and openings in the building envelope, adding to both heating and cooling loads.

Question 3

Which of the following best describes a 'dedicated outdoor air system' (DOAS)?

Accepted Answer

A separate system that provides pre-conditioned outdoor air to each zone independent of sensible cooling/heating equipment

Answer

A DOAS handles ventilation by conditioning 100% outdoor air to neutral conditions before delivering it to zones, while separate equipment (fan-coils, radiant panels) handles sensible loads.

Question 4

When designing refrigerant piping for a split system with the outdoor unit above the indoor unit, what special design consideration is required?

Accepted Answer

Adding oil traps in the suction line riser at regular intervals

Answer

When the compressor is above the evaporator, suction line risers need oil traps (P-traps) at the bottom and at every 20 feet of vertical rise to return lubricating oil to the compressor.

Question 5

In HVAC system design, 'diversity factor' is applied to:

Accepted Answer

Reduce the total calculated peak load when all zones are unlikely to peak simultaneously

Answer

A diversity factor reduces the sum of individual zone peak loads to reflect that zones rarely all peak at the same time, allowing smaller central plant equipment.

HVAC Practice Test

HVAC Practice Test

HVAC System Design 5