Axial Ventilating Fans.

TM 55-1905-223-24-17

(5) Element Failure.

(a) Excessive overheating with wrong temperature or bypassed primary limit control.

(b) Improper filtering so that elements can not dissipate heat through dirty covering.

(d) Any physical damage, ground, or nick in the element itself.

b. Axial Ventilating Fans.

(1) Axial fans, as all fans, are sensitive to inlet and outlet conditions. Disturbances or obstructions of

air intakes and discharges will not allow the normal velocity to develop, and will result in loss of

performance.

(2) The impeller (blades) in an axial flow fan must be kept reasonably clean if it is to perform properly.

Supply air ventilating fans will seldom need cleaning. Exhaust air fans must be checked and

cleaned as required. Dirt or deposits will usually build up on an impeller evenly, and they present

no problem to performance or operation until they become thick enough to break away in crust-like

pieces. When this happens, the impeller may be thrown out of balance and the resulting vibration

could be serious. Any hard, dry layer of dirt and debris must be removed by solvent cleaning or

scraping. Be careful not to cut or scrape through protective coatings or paint on the impeller

blades. Removal of blade coatings, as well as wear from abrasion, can also cause excessive

vibration which will lead to damage of the impeller and other fan components.

(3) Electrical Connections.

(a) Electrical connections must be connected following electrical characteristics as indicated on the

motor nameplate. The wiring diagram on the motor nameplate or terminal box must be strictly

adhered to.

(b) Special attention should be given to being sure that a single phase motor is connected only to a

single phase supply of proper voltage, and that a three phase motor will only operate on a three

phase supply. Electric motors will burn out and fail immediately if improperly connected.

directional arrows on the unit. If the impeller is turning in the wrong direction, it will not deliver

the rated airflow. The motor connections must immediately be altered to correct rotation.

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