Which of the following statements is true...

🔍 Key Concepts

• Auxiliary boiler control devices and what they are designed to do (control vs. protect) • Internal construction of pressuretrols/pressure limit switches (how they sense pressure and operate contacts) • Difference between safety valves (pressure relief) and pressure controls (start/stop or limit firing)

💭 Think About

• Which device on a boiler actually opens to release steam to atmosphere, and which devices only open or close electrical contacts? • Think about what kind of mechanical sensing element is commonly used to convert pressure into motion for a control switch: is it usually a temperature element or a pressure-responsive element like a bellows or diaphragm? • Which option describes a control that stops/starts the burner on pressure, and which options are describing level control or temperature devices instead?

✅ Before You Answer

• Make sure you separate pressure relief devices (safety valves) from pressure-operated electrical switches (they do not vent steam). • Verify which choice clearly mentions a mechanical pressure-sensing element connected to an electrical snap switch rather than temperature or water level sensing. • Eliminate any option that talks about high water level or temperature differentials, since those are not the primary function of pressure limit switches/pressuretrols.

Which of the following statements is true concerning pressure limit switches and pressuretrols installed on auxiliary boilers?

They are bimetallic elements sensing temperature differentials corresponding to pressure changes.

They consist of a bellows assembly, linked with a snap action switch, through a pressure adjusting mechanism.

They automatically relieve excessive steam pressure by acting as a pilot to the safety valve.

They automatically restart the burner sequence via the high water level signal.

🔍 Key Concepts

💭 Think About

✅ Before You Answer