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Resistance-Start Induction-Run Motor

The rotating magnetic field of the resistance-start induction-run motor is produced by the out-of-phase currents in the run and start windings. Since the run winding appears more inductive and less resistive than the start winding, the current flow in the … Continue reading

05. June 2019 by admin
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Return grille sound requirement

Return air grilles should be selected for static pressures. These pressures will provide the required NC rating and conform to the return system performance characteristics. Fan sound power is transmitted through the return air system as well as the supply … Continue reading

04. June 2019 by admin
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HVAC Controlling Casing Noise

Terminal boxes can sometimes be located over noisy areas (corridors, toilet areas or machine equipment rooms), rather than over quiet areas. In quiet areas casing noise can penetrate the suspended ceiling and become objectionable. Enclosures built around the terminal box … Continue reading

03. June 2019 by admin
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Types of Registers and Grilles

The spread of an unrestricted air stream is determined by the grille bar deflection. Grilles with vertical face bars at 0° deflection will have a maximum throw value. As the deflection setting of vertical bars is increased, the air stream … Continue reading

01. June 2019 by admin
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HVAC Air Noise

High velocities in the duct or diffuser typically generate air noise. The flow turbulence in the duct and the excessive pressure reductions in the duct and diffuser system also generate noise. Such noise is most apparent directly under the diffuser. … Continue reading

01. June 2019 by admin
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HVAC Vortex Shedding

Product research in controlling casing noise has developed a new method of reducing radiated noise. The technique is known as vortex shedding. When applied to terminal boxes, casing radiated noise is dramatically lowered. Casing radiation attenuation (CRA) vortex shedders can … Continue reading

30. May 2019 by admin
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HVAC Fire and Smoke Dampers

Ventilating, air-conditioning, and heating ducts provide a path for fire and smoke, which can travel throughout a building. The ordinary types of dampers that are often installed in these ducts depend on gravity-close action or spring-and-level mechanisms. When their releases … Continue reading

27. May 2019 by admin
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Straight Tube Boilers

The STRAIGHT-TUBE class of water-tube boilers includes three types: 1. Sectional-header cross drum 2. Box-header cross drum 3. Box-header longitudinal drum In the SECTIONAL-HEADER CROSS DRUM boiler with vertical headers, the headers are steel boxes into which the tubes are … Continue reading

17. May 2019 by admin
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Horizontal Return Tubular Boiler

A STATIONARY BOILER can be defined as one having a permanent foundation and not easily moved or relocated. A popular type of stationary fire-tube boiler is the HORIZONTAL RETURN TUBULAR (HRT) boiler shown in figure 1-4. The initial cost of … Continue reading

16. May 2019 by admin
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Scotch Marine Boiler

Figure 1-1 is a portable Scotch marine tire-tube boiler. The portable unit can be moved easily and requires only a minimal amount of foundation work. As a complete self-contained unit. its design includes automatic controls. a steel boiler. and burner … Continue reading

15. May 2019 by admin
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