The pressure gauge used in HVAC (Heating, Ventilation, and Air Conditioning) systems is primarily designed to monitor and control the pressure of refrigerants, water, air, and steam to ensure safe and efficient operation of the system.
According to the measurement medium, function, and accuracy, it can be mainly divided into the following categories:
1、 Classified by measuring medium and purpose
Refrigerant pressure gauge (refrigerant gauge)
Purpose: Specifically used on the refrigerant side of refrigeration/air conditioning systems to measure the pressure of refrigerant on the high and low pressure sides. Usually used in conjunction with a vacuum pressure gauge.
Features:
Composite pressure gauge: This is the most commonly used tool by HVAC technicians. It integrates high-pressure gauges, low-pressure gauges, valve groups, and hoses together for system vacuuming, refrigerant charging, pressure detection, and more. The dial usually has saturation temperature markings for common refrigerants such as R22, R410A, R32, R134a.
Accuracy: Generally at level 1.6 or 2.5, sufficient for installation and maintenance.
Material: The internal components need to be resistant to refrigerant and refrigeration oil corrosion, usually using stainless steel or special alloys.
2、 Classified by structure and working principle
1） Bourdon tube pressure gauge
Principle: Drive the pointer by utilizing the deformation characteristics of a curved spring tube (Bourdon tube) with an elliptical cross-section under pressure. This is the most commonly used and economical type for medium and high pressure measurements of water, steam, air, and refrigerants.
2）. Diaphragm/Diaphragm Pressure Gauge
Principle: Pressure acts on the flexible diaphragm and drives the pointer through the transmission mechanism. Suitable for high viscosity, easily crystallizable, corrosive media (such as dirty cooling water), or measuring micro pressure and differential pressure (such as air filter differential pressure gauge).
3）Piezoresistive/Capacitive Digital Pressure Gauge
Principle: Use the electrical signal changes of the pressure sensor to display the pressure value.
Advantages: High precision, digital display capability, output signal (4-20mA, 0-10V) for remote monitoring and building automation systems (BAS). More and more applications are being made in high-end or integrated HVAC projects.
4）Oil filled shock resistant pressure gauge
3、 Summary of Selection Points
When selecting pressure gauges for HVAC systems, the following key parameters should be considered:
Medium: refrigerant, water, steam or air?
Range: The optimal working pressure should be between 1/3 and 2/3 of the dial range.
Accuracy level: 1.6 or 2.5 for regular maintenance; When precise control or measurement is required, choose level 0.5 or 1.0.
Dial diameter: Choose according to installation position and observation distance (such as 50mm, 63mm, 100mm).
Interface material and size: brass, stainless steel, and thread specifications.
Environmental conditions: Whether shock resistance, waterproofing, and corrosion resistance (such as stainless steel casing) are required.
Special functions: whether electrical contact alarm, remote signal transmission, peak value recording, etc. are required.