Dec.2019 31
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Application and Troubleshooting of Fan Coil Unit
 Question one: The fan has small air output and poor air conditioning effect. 

The fan-coil air supply process enters the air duct through the air return port, and then is blown through the coil by the fan and sent into the room.  In order to ensure air quality, a filter screen is usually installed at the air return port to filter dust.
Carefully analyze the reason for the small air volume: under the normal operation of the fan, besides the small air intake volume, there is air leakage in the air duct, and the air leakage in the air duct is rare and well handled.  However, the small air intake is mostly caused by the blockage of the filter screen at the air return port. The solution is to clean the filter screen frequently. If the cleaning is not timely, dust and sundries will further stick to the coil fins and wind wheel blades, and the fins will be blocked by dirt, which will lead to the reduction of the ventilation capacity of the fan.  Dust will also accumulate on the impeller of the fan, causing the angle of the blades to become smaller, thus reducing the air volume and increasing the current of the fan.  Therefore, it is very necessary to clean the filter screen of the air return port in time.  Generally, it is cleaned at least once every quarter, otherwise the blockage will become more and more serious and the maintenance will become more and more difficult.

 Question 2 : The operation noise of coil pipe is large, and the noise increases with the high wind speed. 

This phenomenon generally has the following reasons:
1) Poor shock absorption measures during installation and construction, resulting in resonance during operation;
2) There are foreign bodies in the air duct;
3) Fan blades are deformed or motor bearings are damaged, resulting in poor dynamic balance.
In case of such phenomena, first check whether the coil supports and hangers are loose, then open the air duct to check and remove foreign matters.  Finally, turn the wind wheel by hand to check whether it rotates smoothly and can stop at any position freely.  If you stop at a fixed position freely every time, it indicates that there is a problem with the balance of the impeller and it should be replaced resolutely.  At the same time, check whether there is noise in the rotation of the motor. If the noise is generally caused by abnormal friction caused by damage to the motor bearing, replace the motor bearing.

 Question 3 : coil motor does not turn 

Generally, it can be checked according to the following sequence: firstly, power is sent to check whether the power supply at the coil connection is normal; if there is no power output, first check whether the power supply is faulty, then check whether the speed regulating switch is damaged; if there is power, first, power is sent to check whether there is humming sound and motor heating phenomenon; if there is, turn the impeller hard to see whether it is stuck; if it is not stuck and cannot rotate normally, or if it is turned to a certain angle and stops, it is caused by poor starting performance or large resistance of the motor capacitor or bearing.
Due to the small power of the coil motor and the small starting torque, a slight resistance may cause the motor to be stuck. Foreign matters on the impeller, long-term not use, damage to bearing capacitance, etc. can all cause the motor not to rotate. If with long-term power transmission the motor cannot be started , the temperature of the motor will continuously rise and even burn down. Should be found at any time to repair as soon as possible.

 Question 4 :  the air volume is normal, the supply air temperature is biased 

Most of these failures occur in the coil supply and return system. First check if the water supply temperature is normal and the water volume is normal. If the temperature difference between the supply and return pipes is large, most of them are caused by the plugging of the inlet water filter or the gas in the pipeline. Because the pipeline is blocked or the flow rate of the stored gas will be slower, the time flowing through the coil becomes longer, the heat transfer is sufficient, and the temperature difference between the supply and return water becomes larger. In order to avoid such failures, sharp bends, slag points and gas collection points should be avoided during the construction process. Although the specification requires that the exhaust valve and the blowdown valve should be provided at the high point and low point, the construction site is often difficult to achieve and must be advanced. Planning for serious construction. Flush as much as possible after installation. Always clean the water filter during operation to keep the line open.
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