In the HVAC world, a 3-way globe valve is a workhorse, but if it’s not assembled correctly, it’s just a future service call waiting to happen.
At Boston Aircontrols, we’ve spent more than 25 years helping HVAC contractors get the right parts on the first try. As the region’s #1 Belimo Distributor, we don’t just move boxes, we know the gear. We’ve put together this quick guide (and a hands-on video) to show you exactly how to bench-assemble a 3-way globe valve so it performs exactly as intended.
Watch the Step-by-Step Video
The Pre-Flight Checklist
Before you start, make sure you have the right components. A common mistake is mismatched linkages or actuators that don’t meet the close-off pressure requirements of your building automation system.
1. Identify Your Flow Pattern
The most critical step in a 3-way setup is identifying your flow pattern.
- Mixing Valves: These have two inlets and one outlet. They take hot and cold water to mix them into a single tempered stream.
- Diverting Valves: These have one inlet and two outlets. They take a single stream and divert it to either a coil or a bypass loop.
BAC Pro-Tip: Always look for the directional arrows cast into the bronze or iron body. If you install a mixing valve in a diverting application, you’ll likely deal with “slamming” and premature seat wear due to the flow direction fighting the plug.
2. Ensure Your Linkage is Compatible
Unless you are using a direct-coupled actuator, the linkage is what translates the actuator’s movement into the valve’s stroke.
- Check the Stroke: Ensure the linkage kit matches the specific lift or travel of your valve stem.
- Look for Play: A loose linkage leads to hunting, where the actuator constantly moves back and forth trying to find the right position. At Boston Aircontrols, we ensure your linkage is dialed in for zero-backlash performance.
3. Ensure Your Actuator is Compatible
The actuator is what makes the magic happen, but it has to speak the same language as your building automation system.
- Voltage: Double-check if you’re pulling 24VAC/DC or 120VAC before you wire it up. Frying a brand-new actuator is a bad way to start a Monday!
- Control Signals: Are you running Proportional (2-10VDC / 4-20mA) for precise modulation, or simple On/Off (Floating) control?
- Torque & Close-Off: You need an actuator with enough muscle to close the valve against the system’s pump pressure. For example, the Belimo AFB or NFB series provides high torque and a reliable spring-return safety for when the power goes out.
3-Way Globe Valve Assembly Steps
1. Set the Stem Position
Don’t guess. Check your schematics to see if the valve needs to be Normally Open or Normally Closed to the coil. Manually move the stem to the fail-safe position before mounting the actuator.
2. Secure the Linkage
Thread the valve stem into the linkage carefully. You want a snug fit, but don’t force it. Cross-threading a brass stem is an expensive mistake.
3. Mount and Align the Actuator
Slide the actuator onto the square shaft or linkage. Belimo actuators like the AFB or LMB series make this easy with universal mounting, but ensure the Manual Override is disengaged so the gears can seat properly.
4. The Dry Run
Before you take it to the job site, power the actuator and watch the stroke. It should move smoothly from 0% to 100% without any chatter or stalling.
Best Selling Globe Valves & Actuator Assemblies
Don’t waste time on the job site trying to match incompatible parts. We stock pre-tested Belimo globe valve and actuator assemblies designed for high close-off pressure and precise modulation. Whether you need a stainless steel trim for steam or a bronze body for water service, Boston Aircontrols has exactly what you need.
