1. 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.

2. Short Rules of Unico
A Summary

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

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

5. Unico System Uses Static Regain
An Example of Static Regain

6. 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”

7. 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

8. 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

9. 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

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

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

12. 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

13. 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”