4
ESSENTIAL HYDRONIC HARDWARE
ANSWERS TO TEXTBOOK QUESTIONS AND EXERCISES
1. False. A conventional boiler is intended to operate so that water vapor does not condense
2. False. A condensing boiler is designed to operate with sustained flue gas condensation,
3. Types K, L, and M copper tubing differ in their wall thicknesses. The outside diameter of
4. (a) 0.84 inches
5. Remove it from the valve body or position it away from the heat source to minimize
6. It would cause the valve to close prematurely and greatly limit heat output from the heat
7. A globe valve should not be used for component isolation because it removes
8. A spring-loaded check valve eliminates the orientation restrictions associated with a
9. This is important in order to dissipate incoming turbulence.
10. A 3-way motorized mixing valve has three ports, one inlet port for heated fluid, one inlet
port for cooler fluid, and an outlet port for mixed fluid. The position of the valve’s shaft
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the flow of hot and cool water. A special wax compound within the cartridge expands and
contracts to create movement of the valve’s internal components.
11. It opens or closes the valve. An example is an actuator that operates a 3-way rotary
13. The expansion tank is the point of no pressure change within the system. When the
expansion tank is located close to the circulator inlet, the pressure in most of the system
14. An increase in pressure is the evidence that head energy has been added as fluid flows
16. The end switch in a zone valve closes when the valve is fully open. It signals other
18. A compressed fiber washer
21. 14.67 inches
22. A circulator with a steep pump curve has a greater change in head with a given change in
23. Constant differential pressure control seeks to maintain a constant head and constant
24. Head has units of feet and pressure has units of psi. They are related by the density of the
25. 13 gpm
26. The system curve is as shown.
27. The density of water at 140 degrees F is 61.4 lb/ft3. The pressure differential across the
circulator is 8.53 psi.
28. Assume the water temperature is at 140 degrees F and its density is 61.4 lb/ft3. At 7.5
29. $25.25
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34. The isolation valve protects the air vent from potentially high temperatures and pressures
35. air removal and dirt removal
36. This is important in order to minimize heat loss to the surroundings, due to their large
38. (a) 20.2 psi
39. The lower the average temperature difference across the heat exchanger, the lower the