The type of controller designed to reduce hydro-mechanical stress in the sprinkler system is a ___________ controller.

A soft start controller is specifically designed to manage the start-up process of electric motors used in sprinkler systems, minimizing hydro-mechanical stress. When a pump is powered on abruptly, a sudden surge of water can create a shock wave that can negatively affect the system components, leading to potential damage or inefficiencies.

The soft start controller addresses this issue by gradually ramping up the voltage and current to the motor. This slow increase allows the system to build pressure more gently, substantially reducing water hammer effects and mechanical stress on pipes and fittings.

This gradual approach not only prolongs the lifespan of the sprinkler system components but also enhances overall operational efficiency. Other types of controls, such as a primary resistor, reduced voltage configurations, or wye-delta starters, may not provide the same benefit in terms of soft start capabilities or managing hydraulic shocks effectively, making the soft start controller the most suitable option for the intended purpose.