The maximum horizontal length of a single-wall connector shall be ______ of the height of the chimney or vent.

The correct answer indicates that the maximum horizontal length of a single-wall connector should be 75% of the height of the chimney or vent. This requirement is rooted in safety and efficiency principles for venting systems used in HVAC applications.

When venting exhaust gases, it is crucial to maintain an optimal configuration to ensure proper draft, which facilitates the effective removal of combustion products from the heating equipment. The relationship between the horizontal length of the connector and the height of the chimney or vent plays an important role in maintaining that draft.

By limiting the length of the connector to 75% of the height of the chimney or vent, manufacturers and code authorities aim to minimize the potential for issues like backdrafting or inadequate venting. Longer horizontal runs may lead to increased resistance to flow, which can compromise the effectiveness of the venting system, potentially leading to hazardous situations such as the buildup of toxic gases.

This regulation ensures that the installation adheres to best practices, fostering system efficiency and promoting safety for both equipment operation and occupant health.