HVAC – Strategies for Energy Efficiency – Part 2

HVAC – Strategies for Energy Efficiency While chillers are the largest users of electricity in most commercial facilities, the biggest user of combustible fuels is the heating boiler. The primary cause of energy waste related to boilers is improperly adjusted controls.

Boilers

Efficient combustion of any type of fuel in a boiler requires the proper mixture of fuel and air. Not enough air and fuel will not completely combust, resulting in soot generation that clogs heat transfer surfaces and reduces the boiler’s efficiency. If too much air is introduced it also drops the operating efficiency of the boiler. To ensure higher levels of combustion, all boilers take in more air than is actually required. The excess air does decrease the boiler efficiency and prevents the generation of soot. Industry surveys of boilers show that most systems operate with excess air levels of ten percent or more; this includes oil-fired boilers. Boilers that burn natural gas can operate effectively with three percent excess air. Proper adjustment of the combustion controls will reduce the excess air introduced into the boiler and increase the seasonal operating efficiency. All boilers accumulate deposits within their circulating water that can also build up on the heat- transfer surfaces. Without regular removal of these deposits the boiler’s efficiency will be compromised. Automatic blow down controls remove some of the circulating water and replace it with fresh water. This process, combined with a water treatment system helps to control the accumulation of deposits within the circulating water. Adjusting the rate at which water is removed and replaced within  the boiler system can also improve overall performance of the system. Too high a blow down rate results in energy lost through the discharged water and too low a rate causes scaling to form from a high concentration of solids in the system’s water supply.]]>