When one stops to think that heating is needed during about 7 months out of the year, and that a greater portion of this time is usually moderate weather when a very little heat is needed, it must be seen that the science of running the heater to save coal is to apply common sense rules of limiting the feeding and the attention in such periods. In severe weather we believe in giving the boiler a liberal quantity of fuel regularly and at the right time. The time to save coal is when there is no need for burning it. This is where a great many people make errors in running the boiler—in forgetting to “let up” on the shaking and feeding in moderate weather.
With some drafts and for boilers using hard coal or coke, good economical results often are secured by opening the feed door a little when it is desired to check the fire in moderate weather. This depends on the draft.
For Burning Soft Coal.
—Some types of boilers are made to burn soft coal with economy, with least work. Some types are made specially to burn the meaner grades of soft coal. Firing to prevent smoke is a source of economy and these ways of running should be followed—specially with large sectional boilers.
There are two types of soft coal, viz.: The free-burning coal, which breaks apart when burning, allowing the gases to freely escape; and the fusing-coking coal, which, when burning, first fuses into a solid burning mass with a hard crust over the top, slowly coking as it burns. The latter kind is most valuable for house-heating boilers because the gases are more thoroughly consumed. The fusing-coking coal is worth about 20 per cent. more for this purpose than the free-burning coal.
The gases should be allowed to pass off from the coal slowly. Leave air inlet on the feed door open if draft permits. If possible, use uniform sizes of coal. Avoid using coal having too much dust—the “run-of-the-mine” may be lower in price but its heat-making value is also low.
For the purpose of slow burning of soft coal, it is well in feeding at night to let the fire burn up freely so that the coals are very live with heat. Then fill in enough coal to last all night—leaving some of the live coals uncovered if possible. With large sectional boilers this exposure should be at the rear of the fire so that the flame will pass over the live coals. Thus the gases coming off from the fresh coal are burned and a larger amount of the full heat-producing value of soft coal is made use of and with less smoke.
After a boiler is so fed, the dampers (unless an automatic regulator is used) should be left about as follows:
Ash-pit draft damper open a little or closed, as draft may require.