Diagnostic and Field Testing Flashcards

What is the primary purpose of performing a combustion safety test during a HERS rating?

Answer: To identify carbon monoxide spillage or backdrafting risks in combustion appliances

Combustion safety testing identifies dangerous conditions where combustion byproducts such as carbon monoxide can spill back into living spaces from appliances like furnaces and water heaters.

Which test condition is considered 'worst case' for combustion safety testing of atmospherically vented appliances?

Answer: All exhaust fans on, interior doors closed to maximize depressurization

Worst-case depressurization with all exhaust fans operating and interior doors closed creates the greatest negative pressure that could cause backdrafting.

When using a calibrated manometer to measure pressure difference across the building envelope, the reference port (Channel B) should be placed:

Answer: Outside in an undisturbed location

The reference port must be placed outdoors in a sheltered, undisturbed location to accurately measure the pressure difference between inside and outside.

A HERS rater finds a CO reading of 35 ppm in the flue gases of a natural draft water heater. What is the appropriate action?

Answer: Immediately notify the homeowner and recommend appliance service before occupancy

Any CO detected during combustion safety testing should be reported to the homeowner and serviced before occupancy, as CO poses an immediate health and safety risk.

What does 'spillage' mean in the context of combustion appliance zone (CAZ) testing?

Answer: Combustion byproducts escaping from the draft hood into the living space

Spillage occurs when combustion gases escape through the draft hood or diverter of an atmospherically vented appliance into the surrounding zone instead of exhausting through the flue.

During a pressure diagnostics test, a rater measures -3 Pascals in a bedroom with the door closed and the HVAC system running. This indicates:

Answer: Excessive supply airflow to the bedroom relative to return air capacity

A negative pressure in a bedroom with the door closed indicates more supply air is being delivered than can return, causing the room to be pressurized relative to... actually -3 Pa means the room is slightly negative, indicating insufficient supply or excessive return bypass — but typically a negative room with door closed means the return is pulling more than the supply delivers, suggesting the system is pulling from that room.

Which instrument is specifically used to measure the airflow of individual supply registers during HVAC diagnostics?

Answer: Flow hood (balancing hood)

A flow hood, or balancing hood, is placed directly over a supply or return register to measure the airflow in CFM at that specific outlet.