The magnehelic has a very sensitive diaphragm that responds to changes in pressure. When pressure is exerted on the diaphragm, the dial of the magnehelic responds accordingly and moves to the appropriate pressure. It must be level and in the vertical position when measuring pressure.
Static pressure is measured in inches of water column (“WC) and is the amount of pressure needed to displace one inch of water in a water manometer. A Magnehelic is a brand name for a high-quality Dwyer analog pressure gauge that comes in many different scales.
Set the indicating pointer exactly on the zero mark, using the external zero adjust screw on the cover at the bottom. Note that the zero check or adjustment can only be made with the high and low pressure taps both open to atmosphere.
Differential pressure, or DP or ∆p, is simply the difference between two applied pressures. For example, if the pressure at point A equals 100psi and the pressure at point B equals 60psi, then the differential pressure is 40psi (100psi – 60psi).
If you don’t know how to use one, it’s simple: The Magnehelic is attached to a static pressure tip with a rubber hose. The pressure travels through the tip and the hose, then moves the needle on the gauge. To use a Magnehelic gauge, you’ll need to drill 3/8-in test holes into duct and equipment at the right locations.
Definition of Static Pressure Static pressure, or hydrostatic pressure as it is sometimes called, is the pressure exerted by a fluid at rest. Since the fluid is not moving, static pressure is the result of the fluid’s weight or the force of gravity acting on the particles in the fluid.
To determine operating total external static pressure. Measure pressures where air enters and leaves packaged equipment. Add the two readings together to find total external static pressure. You can still measure the pressure drop of the coil and filter to check for blockage.
The Magnehelic ® gage is the industry standard to measure fan and blower pressures, filter resistance, air velocity, furnace draft, pressure drop across orifice plates, liquid levels with bubbler systems and pressures in fluid amplifier or fluidic systems.
Calibration procedure Check for functionality and any visual defect before calibration. Record all the details about the UUC. Open both ports and exposed to ambient. Connect the pneumatic hose on the positive or high side. Then generate the required pressure (5 test points or as per requirement).
ΔP ( Delta P ) is a mathematical term symbolizing a change (Δ) in pressure ( P ).
HVAC systems use differential pressure switches to measure flow rates and pressures in lines and rooms. These switches help a system to efficiently and economically operate heating, ventilation, and air-conditioning systems. They measure and monitor four key elements in an HVAC system.