Brick Chimney Construction a

BRICK CHIMNEY CONSTRUCTION A brick chimney must be carefully planned. Its size and height must be proportioned to the number, arrangement, and_ size of flues composing it. Modern demands for comfort, attained in cold weather by up-to-date hot-air, steam, and hot-water heating plants, enforce the necessity of accurate chimney construction. Quality of construction is also demanded to reduce the fire hazard to a minimum. Many old buildings confront the heating contractor with flues 4x8 or 4x12 or 4x16 in., showing total disregard of the essentials of draft production.

The chimney-flue of a residence must serve a double purpose: it must maintain a relatively steady draft under varying atmospheric conditions; and it must carry up and away the gases and smoke resulting from the combustion of fuel in the furnace or boiler.

The chimney must have, according to the best modern practice, a draft equaling the pressure of from 15/100 to 2/10 of an inch of water. It must also have sufficient area in square inches at that draft to discharge all smoke and gases at all stages of combustion, from its top, without excess of friction.

The draft of a chimney is affected by varing atmospheric pressures and temperatures, by humidity, and by the quality of the brickwork in its relation to leakage and absorption. The work the chimney is to perform is governed by the quality of the fuel, the quantity of the fuel, and the varying conditions of the fire during the different stages of the fuel's combustion.

Every boiler manufacturer gives the smoke-pipe size for each size and type of boiler he manufactures. It would be manifestly absurd to construct the chimney of a house without giving clue consideration to the demands which will be made upon it when the chimney is called upon to do its work under the most severe conditions. It must always be borne iu mind that the chimney is not meant primarily to be an ornament. Its mission is to provide for the heating of the residence to 70 degrees E. when the outside temperature is zero. Any heating system that can

not do that is not a heating system. If the fault lies with the furnace or boiler, it can be remedied without much trouble by replacing it with a more efficient installation. If the cause of trouble is the chimney, the remedy involves structural changes, iu many cases entailing expense and inconvenience which could have been avoided by intelligent planning in the housebuilding.

There should be no outside interference with the draft of a chimney. The chimney-top should not be lower than any projecting portion of the building, or even on a level with it. If near-by buildings will affect the draft, allowance for this must be made; overhanging trees causing draft interference must also he taken into consideration, and the obstruction removed.

Another evil of chimney construction is that of topping chimneys with capstones whose small openings restrict the area of the chimney's delivery from 20 to 30 per cent. For instance, an 8x 12 chimney with two 5x6-in. holes in its capstone, has its area of delivery reduced from 96 to 60 sq. in.

The intelligent builder will know beforehand the amount of radiation required to heat the house he is going to construct, and will without doubt select the heating equipment which best meets his heating requirements at the time the final plans for the structure are being made.

Table XXX,* which indicates the approximate sizes of chimney-flues for steam and hot-water heating in residences and other buildings, will prove of service to our readers.

The Chimney Flue. It is probable that ninety per cent of the failures of heating apparatus to heat properly (when a heater of sufficient size and the proper amount of radiating surface arc 1.rovided) are directly traceable to the chimney.

Aside from the outlet at the top, the chimney used with any heating apparatus should have no opening except that pansion to overcome this pressure, when it will be forced upward by the circulation caused by opening a draft door below the grate of the heater.