When it comes to diagnostic tools, most HVACR technicians usually carry at least a good electrical measuring meter, refrigerant manifold gauges and a digital thermometer, so they are ready to measure the electrical flow, the refrigerant pressures and the temperatures in a cooling system.

But have you noticed what measuring tool is missing? It’s a sad fact that although it is one of the most critical things to know, few technicians ever carry anything to measure air flow and air pressures. Why not? Because most tools for measuring airflow are very expensive, they are too delicate to carry in a tool box, they need to be constantly recalibrated and most service techs have no idea how to properly use them.

However, there is one tool for measuring both air velocity and pressure differentials that is small, fairly durable, needs no calibration and is relatively inexpensive. It also is simple and easy enough to use that most technicians should have no problem understanding it. What is it? It is the Dwyer 460 air meter.

Is Dwyer paying me to write this article? No. However, this valuable little tool used primarily for residential air-conditioner servicing seems to be the only such tool available in our market.

This little gauge has been around for many years. In fact, it’s been around so long that I used it some 40 or more years ago when I went out on jobs. Is it accurate? It is certainly accurate enough for most service techs to use and it is far better than having no air-measurement tool at all.

How do you use it? Well, it comes with a carrying pouch, two small hoses and two small cups for measuring air velocity, as well as a small slide-rule air-velocity calculator. You connect a hose and a cup to the input of the gauge, face the cup toward the flowing air and a little ball shows the velocity. Also, if you put your finger over the exit portion of the gauge, you can read on the higher-velocity scale, or by connecting the hose to the other (suction) port of the gauge you can read air return velocity.

But that’s not all. Turn the gauge around and connect one hose to a tiny hole you make in the discharge side of an air handler and you can measure the discharge static pressure. Or you can connect the other hose to the air return and measure the suction static pressure. You also can connect a hose to each side of an air filter or an evaporator and determine the pressure losses across them. So if something is stopped up or if there are too many vents closed in a system the problem can easily be read on this simple gauge.

Something that most people don’t realize is that the specification papers for air handlers and for evaporator coils come with charts that show the air-flow volume across clean units, that is, if you can read the static pressure across them. So when such static pressures are read with this gauge, you can quite accurately determine how much air flow is available through the system!

Why am I writing this article?

Because your company needs to offer this service tool and explain to you contractor customers how important it is for their people to have and use it.

As much as a quarter of all servicing problems usually have to do with insufficient air flow and most service techs carry no gauge at all to determine the source of the problem. This is the tool I have used and valued for more than 40 years. It’s an invaluable part of my HVACR tool box.