Direct vent appliances must have the intake and exhaust positioned in what manner?

Direct vent appliances are designed to draw air for combustion from the outside and expel exhaust gases, ensuring efficient operation and safety by preventing backdraft and indoor air contamination. For these appliances, the intake and exhaust must be positioned on the same horizontal plane to facilitate the design's inherent functionality. This configuration allows the appliance to effectively bring in fresh air while securely venting exhaust, minimizing the risk of carbon monoxide entering the living space. Additionally, aligning the intake and exhaust horizontally helps to maintain the efficiency of the venting system and ensures proper airflow.

The other options do not meet the operational requirements of direct vent systems and can potentially lead to unsafe conditions or reduced efficiency. For example, a vertical orientation could make it harder for the appliance to function correctly due to pressure differences. Similarly, positioning at a 30-degree angle might create issues with airflow or improper venting. Separate vertical shafts are unsuitable as they complicate the venting process and negate the advantages of direct vent design.