Plenum Plenum design is based on Equal Static Pressure using Static Regain Most duct systems are designed to maintain Equal Friction or Equal Velocity Static Regain – robs the energy from the moving air (high velocity) to create static pressure to over come friction in the duct so that equal pressure is obtained.

Short Rules of Unico A Summary

Airflow Airflow A MINIMUM OF 200 CFM per ton MUST be maintained at all times

Not Equal Friction This is what most think of for Warm Air Systems

Unico System Uses Static Regain An Example of Static Regain

Plenum Sizing These are MINIMUMS, to be safe you can always use 10” Diameter Max CFM Typical Model 7” 700 1218 or 2430 9” 1000 3642 10* 1300 4860 These are MINIMUMS, to be safe you can always use 10”

Plenum Length – Rule of Thumb Plenum can be up to 150’ equivalent length First Tee = 30’ All other = 15’ Elbows = 15’ Total plenum in the sizes provided can be up to 150’. If the first fitting is a Tee it is equal to 30’. All fittings after that are equal to 15’. Be sure to use 4’ straight duct between fittings – minimum is 2 ‘. 7

60/40 Rule Split 50/50, no more than 60/40 Applies to all tees If you have a tee in the system split the flow as close to 50/50 as possible, no more than 60% of the air flow on either side of the tee. This rule is true for every tee in the system although it is most important for the first tee. Any tees after that can be as much as 80/20 without problems. Q: Assuming that we are using 20 Fully Rate Outlets. What is the max on each side of the tee and of those tees? A: 8

70/30 RULE No more than 30% of CFM on side branch Turn a tee 90 degrees and you have a side branch (do not use the turning vane). The side branch can have no more than 30% of the total CFM. 9

24 Inch Rule You must be a minimum of 24 inches from the exit of the blower before any fitting or take off. 10

Space Takeoffs evenly Maintain spacing between takeoffs as evenly as possible. Minimum 6 inches between takeoffs and 12 inches from end cap. 11

For Every 5 feet Over 10 You Lose 10% of Capacity Keep runs at 12 feet or less (if possible) The longer the run the less air is delivered

Steps to a Unico Layout 1. Do a total load calculation for the buildings 2. Do a room by room load calculation 3. Determine where the air handler/return will go 4. Run the plenum as long as you can to connect the tubing 5. “Connect the Dots”