When brazing/soldering in the horizontal position, where should the filler material be applied first?

When brazing or soldering in the horizontal position, applying the filler material to the bottom side of the joint first is essential for effective heat transfer and ensuring good capillary action. This technique helps the molten filler material to flow into the joint more efficiently due to gravity, as the filler material tends to be drawn into the joint by capillary action when applied in this manner.

By starting at the bottom, it allows the heat to rise and ensures that the filler material properly penetrates the joint, leading to a stronger and more reliable bond. This method is particularly important in maintaining the quality and integrity of the joint, as improper application can result in insufficient bonding or weak spots in the connection. Proper application techniques are crucial for ensuring long-lasting and leak-proof joints in HVAC systems.