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Handbook of air conditioning and refrigeration / Shan K

Handbook of air conditioning and refrigeration / Shan K

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15.28 CHAPTER FIFTEEN<br />

FIGURE 15.23 Drive arrangements for centrifugal <strong>and</strong> axial fans <strong>and</strong> motor positions.<br />

Spark-Resistant Construction<br />

Safety Devices<br />

AMCA specifies three types <strong>of</strong> spark-resistant fan construction:<br />

● Type A construction requires that all parts <strong>of</strong> the fan in contact with the <strong>air</strong> be made <strong>of</strong> nonferrous<br />

metal.<br />

● Type B construction requires that a fan have a nonferrous impeller <strong>and</strong> shaft rings.<br />

● Type C construction requires that a shift <strong>of</strong> the impeller or shaft not allow the ferrous parts to rub<br />

or strike.<br />

The bearings <strong>of</strong> spark-resistant construction fans should not be placed in the <strong>air</strong>stream, <strong>and</strong> all fan<br />

parts should be electrically grounded.<br />

When a fan is installed in a location where it is open to occupants or is accessible during operation,<br />

safety devices such as belt guards <strong>and</strong> protecting screens must be installed. Even a wire mesh<br />

installed at the outlet <strong>of</strong> a fan with a high <strong>air</strong> velocity may cause a pressure loss <strong>of</strong> 0.15 in. WC

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