TinnerFlow™3rd YearYELLOW · Check FirstRound 45 System Effect
A tight pleated elbow can create system effect and turbulence on high-velocity duct. Use an approved smoother/longer-radius fitting or revised route where the system needs it.
Short-radius or light-duty pleated elbows can work in the wrong place, especially near fans, VAV inlets, or high-velocity runs. The air can separate through the turn and create noise, pressure drop, and bad readings.
Replace the restriction with a smoother approved elbow, longer-radius fitting, or revised offset path that fits the pressure class and equipment requirement. Verify the fitting type before assuming any 45° elbow is acceptable.
Do not use a cheap tight 45 elbow in a high-velocity location just because it physically clears the obstruction.
Bad fitting selection can create system effect, noise, pressure loss, and failed balancing.
Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.