Minnesota Boiler License Practice Exam

What is the purpose of a low limit control on a hot water heater?

1. Low limit controls are not used on hot water boilers

2. This control will not allow the burner to leave its low fire position until the temperature in the boiler has passed 150 degrees

3. A low limit control will decrease the pressure on the system

4. This control helps maintain the boiler temperature below a specific limit

The correct answer is: This control will not allow the burner to leave its low fire position until the temperature in the boiler has passed 150 degrees

The purpose of a low limit control on a hot water heater is to ensure safe and efficient operation by preventing the heating system from operating at a low temperature that could lead to issues such as condensation, corrosion, or insufficient heating. When the control is set, it ensures that the burner remains in a low fire state until the water temperature in the boiler rises above the designated threshold, typically around 150 degrees. This mechanism helps maintain a minimum temperature, ensuring that the system heats the water adequately and preventing the risk of any negative effects associated with operating at too low a temperature. The other options do not accurately reflect the function of a low limit control. While some controls may not be applicable to certain systems, the role of regulating burner activity based on temperature is critical for safety and efficiency. Decreasing pressure is not a function of low limit controls; rather, pressure regulation pertains to other aspects of boiler operation. Lastly, maintaining temperatures below a specific limit is more characteristic of high limit controls, which aim to prevent overheating, contrasting the function of low limit controls.