HERS Combustion Safety Questions and Answers

Question 1

A HERS Rater is performing a worst-case depressurization test in a home with a natural draft gas furnace and a gas water heater sharing a common masonry chimney.
The rater first tests the water heater, which fails the spillage test, continuing to spill for more than 60 seconds.
What is the appropriate next step?

Accepted Answer

Stop the worst-case test, return the house to natural conditions, and re-test the water heater for spillage.

Answer

Immediately red-tag the appliance and recommend replacement.

Answer

Proceed to test the furnace under worst-case conditions to see if it also fails.

Answer

Advise the homeowner to have an HVAC technician clean the chimney before any further testing.

Question 2

During combustion safety testing, a rater's personal CO monitor alarms, indicating an ambient carbon monoxide level of 40 ppm in the Combustion Appliance Zone (CAZ). What is the immediate required action?

Accepted Answer

Stop testing, turn off the combustion appliances, ventilate the area, and evacuate the space.

Answer

Continue testing but note the high ambient CO level in the report.

Answer

Put on a respirator and complete the testing protocol as quickly as possible.

Answer

Zero the combustion analyzer in the CAZ and proceed to measure the undiluted flue gases.

Question 3

Which of the following sets of actions is required to establish the 'worst-case' depressurization condition in a Combustion Appliance Zone (CAZ) before testing appliances?

Accepted Answer

Turning on all kitchen and bath exhaust fans, starting the clothes dryer, and closing doors to rooms that make the CAZ pressure more negative.

Answer

Opening all exterior windows, closing all interior doors, and turning on the furnace fan.

Answer

Operating the whole-house ventilation system at its highest setting while opening the door to the CAZ.

Answer

Turning on the air handler, closing all supply registers, and opening all return grilles.

Question 4

A HERS Rater is inspecting a newly installed high-efficiency condensing furnace that is a direct-vent, sealed-combustion unit. The intake and exhaust pipes are routed directly to the outdoors. Which combustion safety test is NOT required for this type of appliance?

Accepted Answer

A worst-case depressurization and spillage test.

Answer

A gas leak check at the pipe fittings near the unit.

Answer

A measurement of carbon monoxide (CO) in the flue gas.

Answer

A visual inspection of the vent terminations for proper clearance.

Question 5

When performing a draft test on a natural draft furnace, the primary purpose is to verify that:

Accepted Answer

A stable, negative pressure is established to continuously move combustion byproducts up the flue.

Answer

The heat exchanger has reached its steady-state efficiency.

Answer

The flue gas temperature is within the manufacturer's specified range.

Answer

The ambient air in the CAZ has sufficient oxygen for complete combustion.

Question 6

During a visual inspection of a natural draft gas furnace installation, which of the following conditions found on the metal flue vent connector is an immediate safety concern that must be noted for correction?

Accepted Answer

The vent connector slopes downward from the appliance to the chimney.

Answer

The vent connector has a total of two 90-degree elbows.

Answer

The vent connector is single-wall galvanized steel.

Answer

The vent connector is secured at each joint with three sheet metal screws.