BPI HVAC Systems 5 — Questions and Answers
Question 1: In the context of BPI whole-house assessments, what does the term 'infiltration' describe?
- Intentional outdoor air supplied by mechanical ventilation
- Uncontrolled air leakage into a building through the envelope (Correct answer)
- Air movement between floors via interior partition leaks
- Exhaust air removed by bathroom and kitchen fans
Correct answer: Uncontrolled air leakage into a building through the envelope
Infiltration refers to uncontrolled, unintentional outdoor air entering a building through gaps, cracks, and penetrations in the building envelope.
Question 2: A homeowner has a condensing (high-efficiency) gas furnace that drains condensate. The condensate line freezes in winter, causing the furnace to shut down. What is the BEST long-term solution?
- Increase furnace fan speed to raise cabinet temperature
- Re-route or insulate the condensate line to prevent freezing (Correct answer)
- Switch to a standard 80% AFUE furnace to eliminate condensate
- Install a larger condensate trap
Correct answer: Re-route or insulate the condensate line to prevent freezing
Re-routing the condensate drain to a warm interior location or insulating exposed sections prevents freezing without sacrificing equipment efficiency.
Question 3: What does an Energy Recovery Ventilator (ERV) do differently than a Heat Recovery Ventilator (HRV)?
- ERV transfers only sensible heat; HRV transfers both heat and moisture
- ERV transfers both sensible heat and moisture; HRV transfers only sensible heat (Correct answer)
- ERV uses a refrigeration cycle; HRV uses a heat wheel
- ERV is for cooling climates only; HRV is for heating climates only
Correct answer: ERV transfers both sensible heat and moisture; HRV transfers only sensible heat
An ERV exchanges both sensible heat and moisture (latent energy) between incoming and outgoing airstreams, while an HRV exchanges sensible heat only.
Question 4: What is the recommended practice when a BPI energy auditor finds existing knob-and-tube (K&T) wiring in an attic that is to receive blown-in insulation?
- Proceed with insulation installation as normal
- Install insulation only up to the wiring and leave a gap
- Consult an electrician before insulating, as K&T must not be covered (Correct answer)
- Replace all insulation with rigid foam to safely cover K&T
Correct answer: Consult an electrician before insulating, as K&T must not be covered
Knob-and-tube wiring relies on free-air cooling and must not be covered with insulation; an electrician must evaluate or replace it before any insulation is added.
Question 5: Which of the following best describes the 'stack effect' in a tall building during cold weather?
- Warm air sinks from upper floors to lower floors
- Cold outdoor air rises through the building due to wind pressure
- Warm indoor air rises and exits near the top while cold air enters at the bottom (Correct answer)
- Exhaust fans pull air uniformly through all floors simultaneously
Correct answer: Warm indoor air rises and exits near the top while cold air enters at the bottom
During cold weather, buoyant warm interior air rises and exits through upper openings while cold outdoor air infiltrates through lower openings, creating a chimney-like effect.
Question 6: When performing a combustion analysis on a natural-draft gas water heater, which measurement confirms adequate draft is occurring?
- Positive static pressure at the draft hood
- Negative static pressure (draft) at the draft hood (Correct answer)
- CO2 reading above 12% at the flue
- Flue gas temperature below 200°F
Correct answer: Negative static pressure (draft) at the draft hood
A negative pressure reading at the draft hood confirms that flue gases are being drawn up and out of the appliance rather than spilling into the living space.
Question 7: A high-velocity, small-duct HVAC system differs from conventional systems primarily in that it:
- Operates at lower static pressure with larger ducts
- Uses 2-inch diameter ducts and higher air velocity to deliver conditioned air (Correct answer)
- Requires no return air system
- Cannot be used for cooling, only heating
Correct answer: Uses 2-inch diameter ducts and higher air velocity to deliver conditioned air
High-velocity systems use small (typically 2-inch) flexible ducts operating at higher velocities to distribute conditioned air with minimal duct space requirements.
BPI HVAC Systems 5
In the context of BPI whole-house assessments, what does the term 'infiltration' describe?