If “automatic” air valves are used they must be carefully adjusted by the steam-fitter and then left to operate without undue interference.
End of the Season.
—At the close of the heating season fill the steam boiler with water to the safety valve and let it thus stand through the summer.
Also thoroughly clean all the fire and flue surfaces of the boiler and at the opening of the next season withdraw the water and refill with fresh water to the water line, starting the boiler as before.
It is advisable to have a competent steam-fitter blow off the boiler under pressure and thus give the inside a thorough cleaning when the boiler is first set up and ready for fire.
A low-pressure boiler, using good water, rarely needs blowing off after it is once cleaned at time of setting up.
THE RIGHT CHIMNEY FLUE
The area of the flue should never be less than 8 inches in diameter if round, or 8 by 8 inches if square—unless for a very small heating boiler or tank heater. Nine or 10 inches round, or 8 by 12 rectangular is a good average size. The flue should generally have a little more area than that of the connecting smoke pipes.
Draft force depends very much on the height of the flue.
The chimney top should run above the highest part of the roof and should be so located with reference to any higher buildings nearby that the prevailing wind currents will not form eddies which will force the air downward in the shaft. Often a shifting cowl which will always turn the outlet away from the source of adverse currents will promote better draft.