12. Describe briefly one form of grease extractor.

13. What is the office of a pressure reducing valve in an exhaust steam heating system?

14. Upon what principle does a pump governor operate?

15. What type of pipe fittings should always be used in hot water work?

16. How is the water of condensation returned to the boilers in exhaust steam heating?

17. How many cubic feet of air per hour will be discharged through a flue 2 feet by 3 feet and 60 feet high, if the air in the flue has a temperature of 80 degrees and the outside air 60 degrees?

Ans. 134,280 cubic feet.

18. In a hot water heating system what causes the water to flow through the pipes and radiators? How does the height of the radiator above the boiler effect the flow?

19. What precaution should always be taken before starting a fire under a steam boiler?

20. What is the free opening in square feet through a register 24 inches by 48 inches? Ans. 5.3 square feet.

21. Why are return pumps or return traps necessary in exhaust steam heating plants?

22. What efficiency may be obtained from indirect hot water radiators under usual conditions? What is the common method of computing indirect hot water surface for dwelling house work?

23. State briefly how a return trap operates.

24. What is the use of an expansion tank, and what should be its capacity?

25. Describe the action of one form of damper regulator.

26. What is the principal difference between a hot water heater and a steam boiler? What type of heater is best adapted to the warming of dwelling houses?

27. Upon what four conditions does the size of a pipe to supply any given radiator depend?

28. What is the use of an exhaust head ?

29. A hospital ward requires 60,000 cubic feet of air per hour for ventilation, and the heat loss through walls and windows is 140,000 B. T. U. per hour. How many square feet of indirect radiation will be required in zero weather?

Ans. 491 sq. ft

30. For what purpose is a back-pressure valve used?

31. A hospital ward is warmed by direct heat and it is desired to add ventilation by using indirect radiators for warming the air supply. The ward has 20 occupants. How many square feet of indirect surface will be required when it is 10 degrees below zero, allowing an efficiency of 660 ?

Ans. 211 sq. ft.

32. A first floor class-room in a high school had 40 pupils, how many square feet area should the vent flue have ?

Ans. 5.8 sq. ft.

33. A private grammar school room having 15 pupils is heated by direct hot water. It is decided to increase the size of boiler and introduce ventilation by means of indirect hot water radiation. How many more square feet of grate surface will be required in the new boiler for zero weather ?

Review Questions On The Subject Of Heating And Ventilation. Part III

1. A main heater contains 1,040 square feet of heating surface made up of wrought iron pipe, and is used in connection with a fan which delivers 528,000 cubic feet of air per hour. The heater is 20 pipes deep and has a free area between the pipes of 11 square feet. If air is taken at zero, to what temperature will it be raised with steam at 5 pounds pressure?

Ans. 140°.

2. A nine-foot fan running at 130 revolutions delivers 40,000 cubic feet of air per minute. If the fan is speeded up to 169 revolutions, and an electric motor substituted for the engine, what will be the rating of the required motor?

3. What precaution must be taken in connecting the radiators in tali buildings.

4. Give the size of heater from Table II, which will be required to raise 672,000 cubic feet of air per hour, from 10° below zero to 90°, with a steam pressure of 20 pounds. If the air quantity is raised to 840,000 cubic feet per hour through the same heater, what will be the resulting temperature with all other conditions the same?

Ans. 85.5°.

5. A fan running at 150 revolutions produces a pressure of 1/2 ounce. If the speed is increased to 210 revolutions, what will be the resulting pressure ?

6. A certain fan is delivering 12,000 cubic feet of air per minute, at a speed of 200 revolutions. It is desired to increase the amount to 18,000 cubic feet. What will be the required speed? If the original power required to run the fan was 4 H. P., what will be the final power due to the increased speed?

7. What size fan will be required to supply a schoolhouae having 300 pupils, if each is to be provided with 3,000 cubic feet of air per hour? What speed of fan will be required, and what H. P. of engine?

8. What advantages has the plenum method of ventilation over the exhaust method?

9. A church is to be warmed and ventilated by means of a fan and heater. The air supply is to be 300,000 cubic feet per hour. The heat loss through walls and windows is 200,000 B. T. U., when it is 10° below zero. How many square feet of heating surface will be required, and how many rows of pipe deep must the heater be with steam at 5 pounds pressure?

Ans. 14 rows.

10. A schoolhouse requiring 600,000 cubic feet of air per hour is to be supplied with a cast iron sectional heater. How many square feet of radiating surface will be required to raise the air from 10° below zero to 70° above, with a steam pressure of 20 pounds?

Ans. 528 square feet.

11. What velocities of air-flow in the main duct and branches are commonly used in connection with a fan system?

12. A main heater is to be designed for use in connection with a fan. How many square feet of radiation will be required to warm 1,000,000 cubic feet of air per hour, from a temperature of 10° below zero to 70° above, with a steam pressure of 20 pounds and a velocity of 800 feet per minute between the pipes of the heater ? How many rows of pipe deep must the heater be?

Ans. 882 square feet.

13. State in a brief manner the essential parts of a system of automatic temperature control.

14. What advantage does an indirect steam heating system have over furnace heating in schoolhouse work ?

15. The air in a restaurant kitchen is to be changed every 10 minutes by means of a disc fan. The room is 20 X 30 X 10. Give size and speed of fan and H. P. of motor.