Boiler Must Be Selected Considering The Individual Project Application

Boilers in India or anywhere else are the basic foundation of heating and domestic hot water in many commercial, industrial, institutional, and education facilities. The term "boiler" can be misleading because in many applications, the boiler does not produce water at boiling temperatures of 212 F or above. Traditional hot water applications typically consist of a medium water temperature system with a minimum of two boilers piped in parallel in a primary heating water loop configuration. There are two types of efficiencies with fuel fired boilers: combustion efficiency and thermal efficiency. Combustion efficiency is the percentage of chemical potential energy of the fuel that is converted during the combustion process to produce thermal energy. Thermal efficiency is simply stated as the percentage of potential fuel energy that is converted to thermal energy leaving the boiler in the form of heated water or steam. It is thermal efficiency that the consulting specifying engineer should be most concerned with in the equipment selection process.

Boilers, in general terms, fall into two main categories with each main category having several types based on type and purpose for each design. The main categories are hot water and steam and this means that there are hot water boilers and steam boilers. To maximize boiler and ultimately the heating system efficiency, the boiler controllability or "turn-down" ratio must be carefully considered for the individual project application. Boiler systems should be selected and sized to allow for a wide fluctuation in the heating load of the building, thus allowing the system to closely match the building heating requirements at any given time. Traditional training of many HVAC engineers and designers is to provide two boilers each sized at two thirds of the total heating load. The thought behind this method considers the fact that if the heating load calculation was performed properly, one boiler will be sufficient during a typical winter’s day. The second boiler will effectively serve as a 100% backup on a typical day. This type of design also allows for proper heating of the building during the most extreme cold weather. Flexible water tube boilers typically consist of an upper and lower water drum with a series of bent steel tubes designed to absorb the stresses of thermal expansion.While this is a good conservative approach and has served the industry well over the years, it may not be the most efficient application due to the controllability of the boilers selected. Many smaller boilers have high and low fire settings that do not allow for matching of the boiler capacity to the actual building load.