Written by HVAC Professionals for HVAC Professionals

Dwyer® 460 Air Meter and Draft Gauge

The Dwyer® Model 460 Air Meter/Draft Gauge is a low-cost instrument that is essential for anyone who diagnoses carbon monoxide (CO) and combustion problems on vented equipment.

This package is for natural draft (drafthood) and induced draft (80%) equipment. Without the Dwyer 460, you could easily misdiagnose a problem contributing to dangerous combustion readings.

With proper training, the draft gauge will tell you if there is enough combustion air available for the equipment and that no building pressure changes are interfering with equipment operation. In a few short steps, it can also tell you if a flue is restricted or undersized.

What it Does and Doesn’t Do

Contrary to popular belief, the draft gauge cannot verify proper equipment venting. You’ll need a combustion analyzer for that. The Dwyer 460 is an inexpensive and versatile solution for most draft pressure measurement applications. It comes with the following:

• Carrying case
• Dwyer 460 Air Meter / Draft Gauge
• 4-ft. length of pressure tubing
• Air velocity calculator
• Various probes and accessories.

We measure draft pressure in inches of water column (in. w.c.). The Dwyer 460 measures up to one-hundreth of an inch of pressure (.01-in. w.c.) and is very sensitive to pressure changes. To get this feature in a digital manometer, it would cost hundreds of dollars.

Pressure tubing connects the draft gauge to a curved metal probe that you insert into the flue for draft measurement. A small white ball inside the draft gauge moves up and down freely to indicate the draft pressure reading on the gauge’s black scale.

Occasionally, inside the gauge may get damp from flue gas. To keep the ball moving freely, clean the gauge regularly.
If you want to learn more about the Dwyer 460, go to the NCI Store at ncilink.com/Dwyer460.

— by David Richardson, Director of Technical Curriculum and Instructor, NCI