Application and troubleshooting of fan coil and electric valve
As a terminal device of the central air conditioning system, the fan coil unit is widely used in residences, offices, hotels, hospitals and other places because of its compact structure, flexible layout, and easy independent control. It consists of a speed-regulating fan and a heat exchange coil. The fan is generally composed of a forward-tilted blade and a low-noise motor. Generally, there are three wind speeds. The motor is tapped to adjust the speed. The speed-regulating switch is used to switch on different taps to control the work of the motor. Voltage to achieve speed regulation. The coil is a high-efficiency finned heat exchanger, which is made of copper tubes and hydrophilic aluminum fins through high-pressure expansion. It is a part of cooling and heating air. In addition, there are accessories such as condensate pans and air filters.
1. The air output of the fan is small and the air conditioning effect is poor
The air supply process of the fan coil is to enter the air duct through the return air inlet, and then the fan blows through the coil and sends it into the room. In order to ensure air quality, a filter is generally installed at the air return to filter dust.
Carefully analyze the reasons for the small air volume: under normal operation of the fan, except for the small air inlet volume, the air duct leaks. The air duct leakage rarely occurs and it is easy to handle. The small air intake is mostly caused by the clogging of the return air filter. The solution is to clean the filter frequently. If it is not cleaned in time, dust and debris will further stick to the coil fins and rotor blades. Blocked by dirt, it will reduce the ventilation capacity of the fan. Dust will also accumulate on the fan impeller, causing the blade angle to become smaller and the air volume to decrease and the fan current to increase. Therefore, it is very necessary to clean the return air filter in time. It is generally cleaned at least once a quarter, otherwise the blockage will become more and more serious and maintenance will become more and more difficult.
2. The coil runs noisy, and the noise increases with high wind speed
This phenomenon generally has the following reasons: 1) Poor damping measures during installation and construction, and resonance occurs during operation; 2) There are foreign objects in the air duct; 3) The fan blade is deformed or the motor bearing is damaged, and the dynamic balance is deteriorated. In case of this kind of phenomenon, please check whether the coil support and hanger is loose, and then open the air duct to check and remove foreign objects. Finally, turn the wind wheel by hand to check whether the rotation is stable and whether it can stop at any position freely. If you stop freely at a certain fixed position every time, it indicates that there is a problem with the balance of the impeller and should be resolutely replaced. At the same time, check whether there is noise in the motor rotation. If there is noise, it is usually caused by abnormal friction of the motor bearing. Replace the motor bearing.
In order to avoid this kind of phenomenon, pay attention to the following during the construction process: 1) Use vibration damping support and hanger to install the coil; 2) Pay attention to the fixed points of each connection must be firm to avoid loosening and falling objects during use. In the maintenance phase, always check and clean, and pay attention to the temperature of the motor and shaft, and often oil and lubricate the bearings.
3, the coil motor does not rotate
Generally, you can check in the following order: first check whether the power supply at the coil connection is normal. If there is no power output, check whether the power supply is faulty, and then check whether the speed control switch is damaged. If there is power, first check whether the power supply is buzzing. If there is humming and motor heating phenomenon, turn the impeller forcefully to see if it is stuck. If it is not stuck and cannot rotate normally, or it stops at a certain angle, it is because the motor capacitor or bearing is damaged, the starting performance is poor or Caused by high resistance.
Due to the low power of the coil motor, the starting torque is not large, and a slight resistance may be stuck. Foreign objects on the impeller, long-term use, bearing capacitor damage, etc. can cause the motor to not rotate. Failure to start will cause the temperature of the motor to continue to rise, or even burn. It should be checked and repaired as soon as possible.
4. The air output is normal, and the air supply temperature has deviation
This type of failure mostly lies in the coil water supply and return system. First check whether the water supply temperature is normal and whether the water volume is normal. If the temperature difference between the supply and return pipes is large, it is mostly caused by the blockage of the water inlet filter or the gas in the pipe. Because the pipeline is clogged or the air flow speed will slow down, the time to flow through the coil will be longer, the heat exchange will be sufficient, and the temperature difference between the supply and return water will increase. In order to avoid such failures, sharp bends, slag storage points and gas gathering points should be avoided during the construction process. Although the specification requires that exhaust valves and sewage valves should be installed at high and low points, it is often difficult to achieve on the construction site and must be implemented in advance. Plan serious construction. After the installation is complete, flush as much sewage as possible. Clean the water filter frequently during operation to keep the pipeline unobstructed.
5. Water dripping from equipment and pipelines
This fault mostly occurs during the summer cooling period, and is mostly caused by poor insulation and poor drainage of the condensate pipeline. Generally, there are special-shaped pipe fittings such as valves, filters and hoses in the pipeline connected to the coil at the engineering site. The heat preservation is not easy to compact, and it is often disassembled during routine maintenance, which can easily cause condensation and water leakage. In engineering practice, the supply can be used. The return water partial pipeline slopes to the side of the coil to prevent and remedy. Or adopt the method of adding a water tray externally. Use partial heat preservation to make detachable heat preservation pipes. It is to make a mold in the same project and use polyurethane foam to make a detachable insulation pipe. After each disassembly, only a thin layer of rubber and plastic insulation is replaced close to the pipe. Then put on the finished insulation tube and wrap it tightly.
Poor drainage of condensate is mostly manifested as water overflowing from the condensate receiving pan of a coil in the same system. During the operation of the air-conditioning system, excessive local stress or failure of supports and hangers can easily cause slope changes or local water retention, which can easily cause condensate overflow. This requires strict control of the slope of the water pipe during installation, and dredge and control the drainage pipeline. Reasonable distance from other pipes. Do not lean too close to prevent accidental deformation. And check the mounting and fixing points of the support and hanger to prevent deformation and falling off. One thing that needs to be explained is that during the construction process, some people think that as long as the condensate pipe network enters the water from the high point of z*, the water can be discharged from the low point of z*. However, it is not enough to only be able to discharge water. It is also necessary to ensure the same amount of water in and out. Just work. Otherwise, there will be local water retention problems. These places are also easy to accumulate impurities and bacterial moss, etc., which will easily block the pipeline for a long time. This kind of problem must be strengthened in construction management, and it is difficult to find and deal with it after the condensate pipe is insulated. Source of this article: Refrigeration Encyclopedia WeChat public account.
In terms of water pipe material, it is recommended to use PVC pipe instead of steel pipe in terms of convenience for use and maintenance. Because the inner wall of the steel pipe is not as smooth as the PVC pipe, it is easy to rust. It is easy to accumulate impurities and block the pipeline. During the commissioning phase, the water receiving pan should be cleaned frequently during routine maintenance to prevent impurities from entering the pipeline and keep the condensate pipeline unobstructed. And often check the tightness of pipeline insulation. Do not leak water, otherwise it is easy to pollute the ceiling and cause great trouble.
Fan coil is a common end spare part of central air conditioner, mainly composed of low-noise motor, coil, etc. The fan cools or heats indoor air or outdoor mixed air through a surface cooler and sends it into the room, thereby changing the indoor temperature to meet people's temperature requirements. The following is an introduction to the common failures of fan coil units and their causes.
6. Common failures of fan coil units and their causes
1) Improper setting of the air supply gear, excessive dust accumulation in the filter, excessive dust accumulation between the coil fins, low voltage, and reverse fan rotation.
Form of expression: the fan rotates but the air volume is small or no wind
2) The fan bearing is poorly lubricated or damaged, the fan blade is too dusty or damaged, the fan impeller and the casing are rubbed, the air outlet and the external air duct or the air outlet are not softly connected, the coil and the drip tray and the water supply and return pipe and drainage The tube is not a flexible connection, the fan coil is running at high speed, the connecting piece of the fixed fan is loose, and the air supply louver is loose. Source of this article: Refrigeration Encyclopedia WeChat public account.
Form of expression: vibration and noise are too large
3) During the hydraulic strength test and tightness test of the pipeline system, only the pressure value and water level change are observed, and the leakage check is not enough.
Manifestation: Leakage occurs after the pipeline system is running, which affects normal use.
4) Improper temperature gear setting, air in the coil, abnormal water supply temperature, insufficient water supply, oxidation of the coil fins.
Form of expression: the wind blowing is not cold enough (hot)
5) The condensate pipe is concealed without closing the water test.
Forms of expression: May cause water leakage and cause user losses.
6) The fan coil selection system was not flushed carefully before the completion of the construction, and the flow and speed did not meet the pipeline flushing requirements. It even replaces flushing with water pressure strength test.
manifestation: water quality does not meet the requirements of the pipeline system operation, often resulting in reduction or blockage of the pipeline section.
7) Water pressure test under negative temperature during winter construction.
Form of expression: The tube freezes due to the rapid freezing in the tube during the hydraulic test.
8) After the pipeline water test in cold areas, the water in the pipeline was not drained in time in winter.
Manifestations: pipelines and parts are frozen and damaged, causing water shutdown for repairs, affecting normal production and domestic water.
9) When the concealed project is not inspected or failed, the next process construction will start.
Forms of expression: hidden dangers left by the project, which often result in rework losses.
10) The same type of room with the same pipeline will not be a model room.
Forms of expression: the same water pipes in the room are caused by different practices, and the size of the mouth is not uniform, causing rework.
11) The flange and gasket of the pipe connection are not strong enough, and the connecting bolts are short or have a small diameter. Heat pipes use rubber pads, cold water pipes use asbestos pads, and use double-layer pads or inclined pads, flange pads projecting into the pipe.
Form of expression: The flange connection is not tight, or even damaged, and there is leakage. The flange gasket protruding into the pipe will increase the water flow resistance.
