Most of the time, a properly designed Arzel Zoning system won't need bypass. When you do need bypass, here's how to set up the ModuPASS® modulating bypass system.
When it comes to using a bypass in zoning application it’s only about objectional airflow noise. What you’re going to find is that when a zoning system is designed appropriately, your static pressure numbers are going to be within range of what your furnace is designed to handle, but on those smaller zones there might be more noise coming from the registers than necessary. Your perception of noise is different than your homeowner’s. So what you want to do is you want to look at your static pressure and come up with a good roundabout number where you find most of your customers are happy at. For myself I found my customers were happy if I had an external static pressure between 0.2 and 0.25. That also gave me a total external static pressure in most cases around 0.7, which was within range for what my furnace was designed to handle.
The Arzel ModuPASS is going to control your static pressure. The transmitter here has 14 full turns to it. Counterclockwise is going to close; clockwise is going to open. So when you’re making your adjustments, you’re going to watch your monometer and you’re going to see how that pressure changes. The first thing you do is you start with it in the fully closed position, and then start turning that dial. With 14 full turns you’re going to be turning it for a second. But you’re listening for the air pressure to bleed off. Right now we’re starting with a total external static pressure of 0.8 and like I mentioned earlier, when I was installing Arzel in the field most of my customers were happy around a 0.7, so that’s what I’m aiming for.
Once I hear that pressure bleed off I’ll just be making small adjustments to it, bringing it down into that 0.8 range, and we can take a look and see where my manometers end up, or my Magnehelic. So I heard the pressure bleed off. I can see the needle moving a little bit. So my pressure is dropping. My total external static pressure starting at a 0.8 you can see it dipping down closer to 0.7 with just small adjustments and then you can see that my external static pressure over here has dropped down to where it’s within range between 0.2 and 0.25. Once I get it there I’ll let my customer listen to it, and if they have a problem with noise then I’m going to adjust it back a little bit further. If they’re happy with it I know that I’m within range for what my equipment’s designed to handle, and I’m going to leave it there.
