The selection process for incorporating electronic controls into a boiler system can be daunting and can vary depending on the application. For the simplest of applications a basic safety relay may be all that is needed. For more complex applications, feature rich controllers that can assist the end user in troubleshooting the heating system are a necessity. No matter what your application, specifying and designing in a controller that meets local and federal regulations is a must. Gems Sensors & Controls, manufacturer of the industry respected Warrick Line of boiler controls, developed this article to help those within the boiler industry understand the codes that cover boiler safety controls.
The days of temperamental boiler systems have all but passed. Nation-wide adoption of safe installation practices, regular maintenance and technological advancements are edging boilers into the category of set it – forget it. This is not to say that accidents have been wholly eliminated. They do still occur, but fortunately the introduction of critical operational and safety controls have significantly lowered the frequency.
The typical steam boiler has at least two or more independent Low Water Fuel Cutoff circuits per CSD-1 code, and the system comprises a water feeder (water make-up) circuit responsible for replenishing water as it is converted to steam. There are both mechanical and electrical means supporting feeder circuits. Shown below is an electrical version using conductivity sensing probes.
According to the American Society of Mechanical Engineers (ASME), the recognized authoritative association dedicated to making a safe boiler industry safer, most problems with boilers result “from a loss of water (low water), pressure vessel explosion, over pressure and over temperature. [Among the list of] principal causes of accidents to automatically fired boilers are lack of proper controls and safety devices … failure to test controls and safety devices.” 
Experts believe that “improved instrumentation, controls and safety devices, proper operating procedures, and a clearer understanding of installation requirements by manufacturers, installers, and operators will greatly reduce the chances of personal injury, damage to property, and the loss of equipment from accidents.” 
Control products must be robust, have a long service life, and be reliable. With all the apparent options available how is an OEM assured that the products they specify will operate safely and reliably in their boiler applications?
 Controls and Safety Devices for Automatically Fired Boilers, The American Society of Mechanical Engineers, 29 December 2006, v.
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