What should the air pressure of the D.P.S be set at if material data is unavailable?

The air pressure of the Dry Pipe System (D.P.S) should ideally be set at a specific level to ensure proper operation, particularly when materials data is unavailable. Setting the pressure at 20 psi over the calculated trip point is a standard practice in the industry. This pressure is sufficient to account for any potential losses and maintain reliable operation of the system.

When the data for the materials used in the system is unknown, it's essential to choose a conservative approach to avoid issues that may arise from insufficient pressure. Setting it at 20 psi above the calculated trip point offers a balance that ensures adequate pressure while also being mindful of the system's operational limits.

Choosing other pressures, such as 15 psi, may run the risk of insufficient operation, especially under varying conditions. Similarly, pressures set at 25 psi or 30 psi could unnecessarily increase the stress on the system components or lead to over pressurization, which can cause issues such as leaks or damage to system components. Hence, the selection of 20 psi over the calculated trip is widely considered to be the optimal choice when specific material data is not available.