HVAC Instruments

Differential pressure gauge

The most common and widely used application area for HVAC differential pressure gauges. Mainly used to monitor the flow resistance of air or liquid to ensure efficient system operation and provide maintenance warnings.
Filter status monitoring:
Air filter: installed before and after the primary and medium filters of the air conditioning unit or fresh air unit. As the filter gradually becomes clogged, the pressure difference before and after it will increase. The reading on the differential pressure gauge can visually indicate whether the filter needs to be cleaned or replaced. This is the most classic application.
Water filter: Monitor whether the Y-shaped filter on the pipeline of the chilled water and cooling water system is clogged.
Fan/duct performance monitoring:
Monitor the pressure difference between the inlet and outlet of the fan to determine if the fan is working properly.
Monitor the pressure situation of the air duct in the variable air volume system.
Cleanroom pressure monitoring:
In clean rooms such as biological laboratories, pharmaceutical factories, and electronic workshops, it is necessary to maintain positive indoor pressure (to prevent external contaminated air from entering) or negative pressure (to prevent harmful substances from escaping from the interior). Acrylic differential pressure gauges are widely used to measure the slight pressure difference between indoor and outdoor or different levels of clean areas.

Pressure range:

0-50Pa/0-100Pa/0-200Pa/0-400Pa/0-500Pa/0-600Pa/0-800Pa/0-1000Pa

-2.5-2.5 mmH₂O/ -5-0-5 mmH₂O/ -7.5-0-7.5 mmH₂O/ -10-0-10 mmH₂O/ -20-0-20 mmH₂O/ -25-0-25 mmH₂O/ -30-0-30 mmH₂O/ -40-0-40 mmH₂O/ -50-0-50 mmH₂O

-25Pa-0-25Pa/ -50Pa-0-50Pa/ -75-0-75Pa/ -100-0-100Pa/ -200-0-200Pa/ -250-0-250Pa/ -300-0-300Pa/ -400-0-400Pa/ -500-0-500Pa

Air Differential Pressure Switch

This is the most common application. Determine whether the system is operating normally by monitoring the pressure difference.
Air filter blockage alarm (HVAC system):
Principle: A clean filter has low airflow resistance and a small pressure difference before and after the filter. As the filter gradually becomes clogged and the resistance increases, the pressure difference before and after it will also increase.
Function: The differential pressure switch sets a pressure difference of “filter needs to be replaced”. When the actual pressure difference exceeds this value, the switch will activate, triggering the alarm light or prompt message on the control panel, reminding the staff to replace the filter in a timely manner to ensure system efficiency and air quality.
Monitoring of fan operation status:
Principle: When the fan is running normally, it will establish a stable pressure in the system.
Function: The differential pressure switch is used to confirm whether the fan has started and is running normally. If the fan malfunctions or the belt breaks, the pressure will disappear and the differential pressure switch will send a fault signal.
2. Process control
Utilize pressure difference to precisely control the process flow.
Boiler furnace pressure safety control:
Principle: The boiler requires stable induced draft, and the internal pressure of the furnace must be slightly lower than atmospheric pressure (negative pressure) to ensure that flames and flue gas will not leak out and ensure safety.
Function: The differential pressure switch monitors the pressure difference between the furnace and the atmosphere. If the furnace pressure becomes too high (positive pressure), the switch will immediately activate to cut off the fuel supply and prevent danger.
Cleanroom pressure control:
Principle: The clean room needs to maintain positive pressure to prevent external polluted air from entering.
Function: The differential pressure switch monitors the pressure difference between the clean room and the external corridor, and links the fan speed or air valve opening to dynamically adjust the air supply volume, ensuring that the pressure difference is always maintained within a safe range.
3. Security protection
As a critical safety interlock device.
Gas equipment flameout protection:
In some gas equipment, differential pressure switches are used to detect whether the airflow required for combustion is normal. If the air pressure is insufficient (such as blockage of the intake duct or fan failure), the switch will not close, and the equipment will be unable to start or immediately shut down to prevent gas accumulation from causing accidents.
Core strengths
Simple and reliable: mechanical structure, sturdy and durable, low failure rate.
Quick response: responds quickly to pressure changes and can promptly issue control or protection signals.
High cost-effectiveness: Compared to complex electronic sensors, it has a price advantage and does not require external power supply (referring to the pure mechanical switch part).
 
Common protection levels:
IP54: Dustproof (limited intrusion) and splash proof. Suitable for most indoor industrial environments.
IP65: Completely dust-proof and water-resistant. It is a common high standard in industrial environments and can be used for spray cleaning or outdoor environments.
IP67: Completely dustproof and can be briefly immersed in water. Suitable for more demanding environments.
Classification: The protection level directly determines the operating environment of the switch. Ordinary distribution boxes can use IP54, while damp and dusty sites require IP65 or higher
ModelAir Differential Pressure Switch
Medium Airnon-combustible and non-aggressive gasses
Max Pressure10 kPa
Mounting positionDiaphragm in any vertical plane
Protection degreeIP54/IP65 (with cover)
Temperature40° C to 85° C
ContactSPDT
Electrical Rating1.5A (0.4A) / 250V
Terminals6.3 mm(0.25″) copper alloy
Connection6.0mm Dia
ApprovalCE/ISO9001
ModelPressure RangDifferentialToleranc
Pa20 ~ 200 Pa10 Pa±15%
Pa30 ~ 300 Pa10 Pa±15%
Pa40 ~ 400 Pa20 Pa±15%
Pa50 ~ 500 Pa20 Pa±15%
Pa200 ~ 1000 Pa100 Pa±15%
Pa500 ~ 2500 Pa150 Pa±15%