Which of the following is NOT a requirement for mechanical draft systems operating under positive vent pressure?

Mechanical draft systems operating under positive vent pressure have specific requirements to ensure safe and efficient operation. One key aspect of these systems is that they must maintain pressure within the venting system to prevent flue gases from escaping into the occupied space.

Sealing all joints is essential because any leaks in the venting system can allow harmful gases to escape, posing safety hazards. Providing a safety interlock with the burner circuit is also important; this prevents the burner from operating unless the draft system is functioning correctly, thus ensuring that flue gases are efficiently vented outside and reducing the risk of backdrafting.

Proper venting to outside air is another critical requirement, as it ensures that the exhaust gases are safely expelled from the building, protecting indoor air quality.

In contrast, being connected to negative draft is not a requirement for systems operating under positive vent pressure. In fact, mechanical draft systems designed to operate under positive pressure are specifically engineered to function with the pressure pushing gases outwards, rather than relying on a negative draft system that draws gases away from the appliance. Therefore, connection to negative draft does not align with the operational principles of positive pressure draft systems and is not a requirement for them.