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Disadvantages of Target Flow Switch

(the copy rights belongs to ZHOU ENSI LTD, reproduce is not allowed)
The target type flow switch is a very old designed flow switch, it have a very long history, the price is getting lower and cheaper. In normal condition, because the target flow plate of the target flow switch is in the bending deformation state under the pressure of water flow for a long time, it is easy to be damaged by fatigue, so the target flow plate of the water chiller maintenance must be replaced after 2 years of installation.

The target type flow switch is listed in the maintenance records as a vulnerable accessory, but some users do not replace it in order to save money. As a result, it always fails during operation.

Target Type Paddle Flow Switches

 Old designed type Target Paddle Flow Switches



It is difficult to find out the failure of target flow fatigue plate, which can not be recovered without special maintenance personnel for small chiller. Only when the chiller fails can it be exposed. In addition, when the water system is mixed with air, the air in the water impacts the target flow plate and causes the flow velocity to drop. The target flow plate resets instantly and sends the wrong flow information to the unit. In order to prevent this kind of error, the unit controller usually delays processing the flow information.


disadvantage of target paddle flow switch


When the flow stop information really occurs, the delay time is enough to freeze the heat exchanger, the faster the chiller with larger refrigeration capacity will freeze, and the differential pressure type flow switch has no misoperation, so the controller does not need to delay the processing of flow information. For the small diameter target type flow switch, a pressure drop of 2 m water column is generated, which reduces the effective head provided to users.


The target type flow switch can not control the flow accurately, because the insertion depth, pipe diameter and water pressure at the installation site of the target flow plate, all of them will directly affect its flow protection value. Even if the flow meter is connected on site to calibrate it, with the accumulation of time, the relationship between the bending degree and flow caused by the fatigue of the target flow plate is also broken, and the originally calibrated flow value also changes

The target flow switch installed in the vertical pipe has a great impact during the start-up and shut-down process, and the target flow plate's service life does not exceed one year, or the bellows inside the target flow switch is broken, which results in water flowing out of the target flow switch. Since the installation of target type flow switch requires a certain amount of straight pipe before and after, if it is installed near the water pipe with a right angle elbow rising, the above situation still occurs

GE-315 Adjustable Paddle Flow switches

GE-315 Adjustable Paddle Flow switches   (New Design)

The GE-315 Series Paddle Water Flow Switch is a new design,  it could avoid the adopt disadvantage of common  target type flow switches.


As the target type flow switch is a part of water and electricity isolation through bellows, the bellows is in contact with the atmosphere. When the temperature of chilled water is too low or lower than the freezing point of water (glycol is added to the water system, to low the freeing temperature), the surface of bellows will condense or freeze, and the surface of micro-switch in the flow switch will also condense, resulting in the increase of contact resistance such as rust and failure

Usually, the target type flow switch is installed in a 1" threaded base, and the threaded base is welded on the main pipe. Due to the rust at the lower part of the threaded base, the target flow plate maybe stuck in the base

In addition, we also found that many engineering installers can't install the target flow switch correctly, which is also the hidden danger of the host's failure, because the installation of the target flow switch's is a little difficult.

There are three general installation conditions:

1. no action
2. stuck in the base or the bottom of pipe, unable to action or recover
3. Success 

Generally, the reason of no action is that the installation depth of the target flow plate is not enough, so it is necessary to screw in or replace the target flow plate again. Many installers often short circuit the water flow switch or adjust the action adjusting screw to make the water chiller lose the water flow protection if they cannot solve this problem quickly.

If it is stuck in the pipe and can not recover, it is often because the target flow plate is too wide that it is stuck in the upper part of the pipe during the first action, which can not be found by the installer. In this case, the flow switch also loses its function. If the installation gap is not enough, even if it can work at that time, the pipe diameter caused by rust or scaling of the pipe will become smaller, which may also cause the water flow switch to be stuck in the pipe.

The third kind of installation is very good, which is closely related to the pipe diameter and the experience of the installation personnel. The larger the pipe diameter is, the higher the accuracy of the primary installation of the target type water flow switch is. After understanding that even experienced installation personnel can not install the target type water flow switch once, the failure rate is more than 60%.


At the end, we recommend the Differential Pressure Type flow switches to you, it could avoid all the above disadvantage of target type paddle flow switch. 


Differential Pressure Flow Switches

GE-511A Differential Pressure type flow Switches with Brass Body to detect the water flow of pump

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