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The Function of Air Differential Pressure Switches in Equipment

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The air differential pressure switch is widely used in gas water heater, wall mounted furnace, gas boiler, various gas equipment, exhaust system and other equipment.

Air differential pressure switch is a kind of detecting element, which is generally used in machinery requiring wind pressure, such as pneumatic press, pneumatic plate shears, gas water heaters, gas boilers, gas furnaces, wall mounted furnaces and other electrical products using gas. It is realized by using gas pressure to push micro switch.

The important function of the air differential pressure switch is to use its on-off ability to control the on-off of the electrical products, so as to ensure that the gas channel can be closed in time when the air exhaust is not smooth, so as to ensure that the gas does not leak out, so as to protect personal safety

The air differential pressure switch has two detection ports, positive pressure detection port and negative pressure detection port. The cavity is also divided into positive pressure cavity and negative pressure cavity. The two chambers are isolated by EPDM membrane. When there is a pressure source, the membrane moves to push the micro switch, then to achieve the purpose of switch open or switch close. The air differential pressure switch is equipped with a fine-tuning device to change the pressure of the spring during the adjustment so as to change the starting point and the shutdown point (i.e. on point and off point) of the air pressure switch.

air differential pressure switches

Air Differential Pressure Switches

GE-924 Adjustable Air Differential Pressure Switch for monitoring over..


Generally, the negative pressure detection port is used for sampling of air differential pressure, and the sampling device is installed in the negative pressure area of the volute of strong exhaust fan. The sampling port of the sampling device is a pipe with an oblique angle. It has a certain angle with the wind flow direction. The pressure value detected varies with the change of the angle and the change of the wind speed.

In order to meet the requirement that the power can not be shut down before 80pa, many factory set the wind pressure value at 110pa to shut down. So, how to accurately control the gas water heater to close at the specified wind pressure value? It use the fine adjustment device of air differential pressure switch to adjust the on point and off point, to match the sampling negative pressure value of the sampling device of the fan to meet the requirements.
air differential pressure transmitter

GE-923 Air Differential Pressure transmitter 4-20mA or 0-5V 0-10V

This GE-923 Air Differential Pressure transmitter is produced with mag...


The sampling process of air differential pressure switch is as follows:
according to the standard requirements, Install the tested exhaust water heater,  connect the exhaust pipe to the air pressure box (the exhaust pipe shall be the maximum length specified in the manual), and connect a tee between the sampling pipe of the fan and the detection port of the air pressure switch to the micro manometer. After starting the water heater, short the wire connected to the air differential pressure switch. Gradually reduce the outlet of the air pressure box. When the pressure of the air pressure box reaches 80pa, observe whether there is flame overflow and other abnormal phenomena around the heat exchanger, and record the pressure P1 displayed on the micro manometer at this time.

Continue to reduce the outlet of the air pressure box. When the pressure value of the air pressure box reaches the set shutdown value (such as 110pa), record the pressure value P2 displayed on the micro manometer, and observe whether the flame overflows. P1 is the minimum value of air pressure switch on point, P2 is the off point value of air differential pressure switch.

It is better to adjust the off point value of the air differential pressure switch to (P2-3) Pa, and it is OK if the on point is less than P1. If the on point value and off point value of the air differential pressure switch have been determined (take the commonly used 39pa air differential pressure switch as an example, the off point value is 39pa, and the on point value is about 65pa): adjust the sampling pipe on the fan when the air pressure box reaches the set shutdown value, so that the negative pressure value displayed on the micro manometer is 36-39pa, and then adjust the pressure value of the air pressure box to 80pa, and then the displayed value on the micro manometer should be greater than 65pa. Then, it can ensure that the water heater can not only work normally when the air pressure box reaches 80pa, but also close when the air pressure box reaches the set value.

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