(a) What is the trouble? (b) Show, by sketches, if necessary, how you would permanently remedy the defect in the most economical manner and without the use of mechanical contrivances.

(28) The loss of heat by conduction and radiation through the walls and windows, etc. of a building, is estimated at 136,000 B.T.U. per hour, (a) What size of a hot-air furnace is required to heat the building to 70° in zero weather, no definite ventilation system being employed? (b) The efficiency of the furnace being 50 per cent., how much coal will be required to heat the building for a period of 24 hours? Assume the calorific power of the coal to be 13,400 B.T.U.

(c) What size of grate will be required, the rate of combustion being 4 pounds per hour per square foot of grate area?

(d) How much heating surface will be required in the furnace, ratio of grate to heating surface being 1 to 45?

(29) In warming and ventilating a building, what provision should be made for controlling the temperature of the incoming air, without changing the volume?

(30) The specific heat of air is .23751; how many B.T.U. are required to raise 20 pounds of air from zero to 160° F.?

Ans. 760,032 B.T.U.

(31) Distinguish between plain and extended surfaces, as these terms are applied to radiators.

(32) A certain building requires 319,000 cubic feet of air per hour, for heating and ventilation. The amount of heat lost from the. rooms by conduction is 275,000 heat units per hour, and the rooms must be maintained at a temperature of 70°; what must be the temperature of the fresh-air supply on entering the room? Ans. 120°.

(33) (a) Distinguish between fire-tube boilers and water-tube boilers. (b) Describe one common form of large water-tube boiler, (c) Describe one common form of large fire-tube boiler.

(34) What are the most important points to be considered in designing a pipe system for the distribution of steam? How should the main be run and graded?

(35) Clearly describe the district system of steam heating, and mention how the connections to the main are made.

(36) Distinguish between a simple-circuit system of hot-water heating and a compound system.

(37) (a) How are 4-inch cast-iron greenhouse pipes joined together? (d) What is the especial advantage in using 4-inch pipes for greenhouse heating?

(38) Describe the process of respiration, and state why buildings should be ventilated.

(39) What provision should be made for properly ventilating a building during summer?

(40) A current of hot air having a temperature of 140° and a volume of 300 cubic feet per minute is cooled to 60° by passing through a room; what amount of heat is given off per minute? Ans. 377.3657 B.T.U.

(41) Describe the most positive and most simple form of pipe coil you can think of, the coil to be set against a wall, and not to exceed 20 feet long or 6 pipes deep.

(42) Distinguish between direct, direct-indirect, and indirect methods of heating buildings.

(43) Briefly describe, in your own language, the principles of operation of the boiler shown in Fig. 48, Heating and Ventilation of Buildings. Mention the use of the several attachments.

(44) Clearly describe how one-pipe riser connections are usually made to the steam main.

(45) In selecting a boiler of the horizontal return-tubular pattern for a hot-water heating system, what should be considered regarding the flue tubes?

(46) Distinguish between open and closed circuits in hot-water heating apparatus.

(47) Mention the principal points to be considered in arranging greenhouse heating pipes. Where should they be located?

(48) What degree of purity in the air is required to constitute good ventilation? Base your answer upon the amount of CO2 present per 10,000 parts of air.

(49) Briefly describe a simple method of ventilating an ordinary dwelling by natural draft, when a hot-air furnace is used.

(50) If 100 cubic feet of air having a temperature of 0° F. enter a hot-air furnace, what will be its volume if delivered at a temperature of 160°? Ans. 134.8 cu. ft, nearly.

(51) Clearly describe the circulation of steam through (a) the Mason tube; (b) the Bundy loop.

(52) Mention the most important matters to be considered in locating the inlet and outlet openings for the ventilation of an ordinary room. State the effect of cold windows upon the natural currents in a room.

(53) What is the horsepower of a boiler?

(54) (a) Clearly describe how steam-radiator connections are usually made on the one-pipe system, (b) How are they made on the two-pipe system?

(55) Describe a hot-water damper regulator, and explain how the dampers are moved.

(56) What do you understand by the one-pipe system in hot-water heating? Describe it.

(57) The grate area of a hot-air furnace is 6.5 square feet. How many square feet of heating surface should the furnace have in order to obtain good results?

(58) What is about the proper degree of humidity for the fresh-air supply to a building in the United States?

(59) Briefly describe a simple method of ventilating a dwelling when steam or hot water is the heating medium.

(60) (a) What kind of resistances must be considered and provided for in designing and erecting a system of air conduits? (d) How can the resistances be reduced to a minimum? (c) Show, by sketch, how you would split a horizontal air-current so as to give an equal supply to three vertical flues.

(61) Clearly describe a box-coil heater which is adapted for heating air by steam, and state the advantages derived from staggering the pipes.

(62) Under what circumstances are overhead heating systems satisfactory? Give your reasons.

(63) How many square feet of heating surface are required to produce 15 horsepower in (a) a return-tubular boiler? {b) a water-tube boiler? (c) a common cast-iron, sectional boiler?