Proportional Method of Balancing of HVAC Systems

Proportional Balancing Method Let’s take a closer look at the steps involved to proportionally balance a multi-story building. A typical school may have two floors with 100 terminal units each, whereas a typical metropolitan building may have 25 floors with 20 terminal units per floor. For illustration purposes, we’ll look at only two floors with three terminals each. All of these principles will apply, regardless of the number of floors and number of terminal units per floor. 1Ensure the system is running wide open. Set all control valves completely open, turn all balancing valves completely open, and ensure the pump is running at design speed. 2Locate the most disadvantaged terminal unit. This is usually the one on the highest floor and furthest from the supply risers. (Figure 2, CBV2-3) This is the starting reference flow. This valve is always left wide open. Note that at this point, the flow through this terminal is likely well below design flow. If not, there is a good chance the pump is severely over-sized. 3Adjust the balancing valves for all other terminal units on the floor (CBV2-2 & CBV2-1) to match the flow that will prevail through the most disadvantaged unit. Note that there is interaction between valves, and as any one is throttled, the flow through the others increases. Experienced balancers can often predict the amount of compensation required for this interaction and can adjust all valves to achieve a common flow through all in just one pass. 4Repeat step 1 to 3 for the next most disadvantaged floor. When complete, each floor will be balanced individually and separate from each other. 5To balance the floors together, leave the riser balancing valve of the most disadvantaged floor wide open (Figure 3, CBVR-2). Adjust the riser valves of other floors, until all floors are at an equal flowrate. 6Throttle the main system balancing valve (CBV Main) to achieve 100% design flow. The entire system is now proportionally balanced, with design flow available to all circuits. However, having the main CBV throttled is like driving a car with one foot to the floor on the gas pedal and the other on the brakes. Though the system is balanced, optimum efficiency is not realized. 7With the system running wide open, measure the pressure drop across CBV main both as throttled and completely open. This pressure difference is the amount of excess pump head generated. 8Shut down the system and have the pump impeller trimmed to eliminate the excess head and bring the pump into the most efficient zone of the performance curve. 9Reinstall the impeller, open CBV main, and verify that design flow is realized. The system is now proportionally balanced with design flow available to all terminal units, and operating at optimum efficiency. 10Release all control valves for normal operation. For Support, please share and subscribe and don't forget to support this channel to continue: For advertising : wardverger@gmail.com To Support: https://paypal.me/AbuWardHVAC?country...   / abuwardhvac   https://paypal.me/AbuWardHVAC?country... Thank you