Auto-Zone Control Systems Zoning Design Guide (Version 01B) - Manual (Page 27)

Auto-Zone Systems 27
Zoning Design Guide
Application Notes:
Zoning 30 And 40 Ton Units
When using large HVAC units for zoning applications,
several rules must be considered to prohibit potential
problems.
Because of the large air flow capacities of the 30 and
40 ton units, great care must be taken in sizing zone
and bypass dampers.
Use these guidelines to help keep you out of trouble.
• Always use the Auto-Zone Plus system even
if you only have one unit that you are zoning.
• Generally you should use constant volume
units in your zoning system design. If your
units are to be equipped with variable
frequency drives or inlet vanes, please
consult WattMaster Controls for assistance.
• The OE340-10-AGSTG relay expansion card
is usually required for each Zone Manager
controlling two or more stages of cooling.
• Bypass dampers should be sized for 60 to
70% of the rated CFM of the unit. Because of
the large air volumes involved, rectangular
dampers should be used instead of round
dampers. Consult the rectangular damper
sizing guide (Table 1-2 on page 25), for CFM
ratings.
• Large units should always have a minimum
of 6 zones due to the high air flow capacities.
• To prevent excessive noise in the system,
zone damper total minimum airflow settings
should be equal to or preferably greater than
30% of the units rated CFM.
As an added precaution, we recommend a high duct
static safety switch be installed (Dwyer Model 1900-
5-MR or equal) to prevent over pressurization of the
ductwork.