ABSTRACT
This chapter demonstrates how to find excess air when either the carbon dioxide or oxygen content of combustion products is known. The infiltration of cold air into boiler or furnace can represent serious energy loss. This usually occurs in negative draft boilers and furnaces where dampers, doors and inspection ports are inadvertently left open or no longer form a tight seal after years of use. Exit gas temperature, should be measured at the boiler outlet, after the economizer or air heater depending on which is last before gasses exit to boiler. If the measurements are not typical, being cooled by wall losses of the duct or stack or by the infiltration of cold air, resulting heat efficiency measurements will be erroneous. A relief valve on a low pressure, 30 psig, header has started to blow steam. An examination of the make-up water readings indicates an increase of 28,776 gallons per day starting when the relief valve began blowing steam.
