In a gas boiler system, the air pressure switch plays a crucial role as the "safety guard" for boiler operation. It monitors the air pressure in the burner's inlet duct to ensure combustion occurs under appropriate air volume conditions, thereby preventing risks such as incomplete combustion, flameout, or even explosions caused by insufficient or excessive air volume. How should one select a suitable air pressure switch from numerous products? This article provides a detailed introduction.
I. Clarify the Working Principle to Lay the Foundation for Selection
The working principle of an air pressure switch for gas boilers is straightforward. Its core component is a pressure sensor. When air pressure acts on the sensor, it deforms, triggering a microswitch to control circuit on/off. In simple terms, when the air pressure reaches the set upper or lower limit, the switch acts to send a signal to the control system, thereby regulating the operation of equipment like fans and burners to ensure boiler safety. For example, when air pressure is too low, the pressure switch cuts off the gas supply to the burner, preventing incomplete combustion (which could generate harmful gases like carbon monoxide) due to insufficient air.
II. Key Points for Selection
(1) Pressure Range
The core parameter of an air pressure switch is its monitored pressure range. A gas boiler's burner requires a specific air pressure to ensure full mixing and combustion of air and gas. Thus, the pressure range of the selected switch must match the actual working air pressure of the boiler burner. Typically, the burner's air pressure ranges from 100 to 500 Pa. If a boiler burner has a rated air pressure of 300 Pa, the air pressure switch should cover this value with a sufficient safety margin—for instance, choosing a range of 200–500 Pa.
(2) Accuracy Grade
Accuracy directly affects the detection precision of the pressure switch. For gas boilers, which require high-pressure control, it is recommended to choose products with high accuracy, such as ±1% FS (full scale) or higher. A high-precision switch can sense pressure changes more accurately, ensuring the boiler operates under optimal air pressure, improving combustion efficiency, and reducing energy waste.
(3) Switch Type
Air pressure switches generally come in three types: normally open (NO), normally closed (NC), and composite. An NO switch closes when the set pressure is reached, an NC switch opens, and a composite switch can be set as NO or NC as needed. For gas boilers, NC air pressure switches are more commonly used. When air pressure drops below the safe value, the NC switch automatically cuts off the power or gas supply to ensure safety. For example, during burner startup, if the air pressure is insufficient, the NC switch prevents the burner from igniting until the air pressure reaches the safe range.
(4) Electrical Parameters
These include rated voltage, rated current, and contact types. The rated voltage and current must be compatible with the gas boiler's control system to avoid malfunctions or equipment damage. Common contact types are NO and NC, selected based on the control system's logic. For example, if the control system needs to connect the circuit when air pressure is normal, an NO contact pressure switch should be chosen.
(5) Matching with the Burner
The air pressure switch must work closely with the burner's control system, which adjusts parameters like fan speed and gas supply based on the switch's signals to ensure stable and safe combustion. Therefore, when selecting a switch, ensure its output signal form matches the input requirements of the burner's control system. For instance, if the burner's control system uses analog signal input, the air pressure switch should output the corresponding analog signal.
Selecting an air pressure switch for a gas boiler requires comprehensive consideration of the working principle, key parameters, brand quality, and practical cases. Only through careful analysis and comparison can the most suitable switch be chosen to ensure the boiler operates safely and efficiently, providing reliable energy support for production and daily life.
