HERS - Certified Home Energy Rating System Rater Combustion Safety Principles Questions and Answers 1 — Questions and Answers
Question 1: A HERS Rater is performing a worst-case depressurization test in a Combustion Appliance Zone (CAZ). After establishing a baseline pressure, which of the following steps should be performed FIRST to create the worst-case scenario?
- Turn on the central forced-air system blower.
- Open all interior doors.
- Turn on all exhaust fans, such as clothes dryers and bathroom fans.
- Close all exterior doors and windows. (Correct answer)
Correct answer: Close all exterior doors and windows.
To create a worst-case depressurization scenario, the house must first be isolated from the outdoors. This is achieved by closing all exterior doors and windows, which is a foundational step before activating any exhaust appliances that would depressurize the house.
Question 2: During a combustion safety inspection, a HERS Rater measures an ambient carbon monoxide (CO) level of 40 ppm in the home. According to RESNET and BPI standards, what is the immediate required action?
- Continue with the inspection while monitoring the CO level.
- Immediately turn off the combustion appliance, ventilate the area, and recommend the occupants evacuate.
- Advise the homeowner to open windows and doors and to contact a qualified professional. (Correct answer)
- Complete the spillage test before taking any further action.
Correct answer: Advise the homeowner to open windows and doors and to contact a qualified professional.
According to combustion safety standards, if ambient CO levels exceed 35 ppm, the test must be stopped. The rater should advise the homeowner of the elevated levels, recommend ventilating the house by opening windows and doors, and advise them to have the potential source (the appliance) checked by a qualified professional. Evacuation is typically required at higher levels (e.g., 70 ppm or greater).
Question 3: Which of the following conditions is most likely to cause backdrafting of a natural draft water heater?
- An oversized chimney flue shared with a high-efficiency furnace.
- A leaky building envelope with significant air infiltration.
- Operation of a powerful, uncompensated kitchen exhaust fan. (Correct answer)
- Low outdoor wind speeds.
Correct answer: Operation of a powerful, uncompensated kitchen exhaust fan.
Powerful exhaust fans can create significant negative pressure within a home. If there is not adequate makeup air, this depressurization can overcome the natural buoyancy of the flue gases in an atmospheric appliance, pulling them back into the living space.
Question 4: When performing a spillage test on a natural draft gas furnace that has been off and has a cold vent, at what point during the main burner operation should spillage be assessed?
- Immediately upon burner ignition.
- At 2 minutes.
- At 5 minutes. (Correct answer)
- After the blower fan has activated.
Correct answer: At 5 minutes.
For a natural draft appliance with a cold vent, it takes time for the flue to warm up and establish a proper draft. Standard protocols, such as those from BPI, require checking for spillage at 5 minutes of main burner operation to allow sufficient time for the draft to establish. Checking earlier may result in a false failure.
Question 5: A homeowner has recently air-sealed their attic and crawlspace. What is the primary combustion safety concern a HERS Rater should investigate related to this work?
- Increased potential for gas leaks due to pressure changes.
- Reduced dilution of potential CO spillage and increased depressurization. (Correct answer)
- Damage to the flue liner from changes in attic temperature.
- Over-firing of the furnace due to restricted combustion air.
Correct answer: Reduced dilution of potential CO spillage and increased depressurization.
Making a house tighter reduces the amount of natural air infiltration. This has two major impacts on combustion safety: 1) it makes the house more susceptible to depressurization from exhaust fans, increasing backdrafting risk, and 2) if spillage does occur, the reduced air exchange rate means the harmful gases, like CO, will not be diluted as quickly, leading to higher concentrations.
Question 6: According to RESNET Standard Chapter 8, which of these tests is a required part of a combustion safety inspection?
- Heat exchanger integrity test using a camera.
- Gas leakage test on all appliance fittings and connections. (Correct answer)
- Measurement of stack temperature for efficiency calculation.
- Visual inspection of the thermostat for proper calibration.
Correct answer: Gas leakage test on all appliance fittings and connections.
RESNET Standard Chapter 8 specifically requires protocols for Carbon Monoxide (CO) testing and Depressurization testing. A critical part of the overall safety check, as outlined in section 802.3, is to perform a gas leakage test on the fittings and connections of gas appliances within the home to identify any potentially hazardous leaks.
HERS - Certified Home Energy Rating System Rater Combustion Safety Principles Questions and Answers 1
A HERS Rater is performing a worst-case depressurization test in a Combustion Appliance Zone (CAZ).
After establishing a baseline pressure, which of the following steps should be performed FIRST to create the worst-case scenario?