Step 3: Set The System Static Pressure - Carrier VVT Zone Installation And Startup Manual

Start-up
Series Fan Zone Terminals only - If the zone maximum heating airflow design requirements are the same
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as cooling, the Heating Max Damper Position should be 100%, same as the Cooling Max Damper
Position. If the heating requirement is less than the cooling requirement, type the appropriate value in
Heating Max Damper Position per the design requirements.
If the terminal has ducted reheat, click Reheat Min to force the zone to its reheat damper position. Type
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the desired damper position next to Reheat Min to adjust the airflow to its design reheat position.
If the zone maximum heating airflow design requirements are the same as cooling, skip this step. If they
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are less than cooling, click Heat Max to force the zone to its maximum heating position. Check the zone
for design heating maximum airflow using certified measuring devices. Type the damper position next to
Heat Max.
10 To set the heating minimum airflow, click Heat Min, then type the damper position. We recommend that
the sum of this setting for all zones in the system be equal to the minimum heat CFM requirements of
the air source.
11 Repeat steps 1 through 10 for each zone until all zones have been balanced.

Step 3: Set the system static pressure

For the air source to deliver the required airflow, you must set the bypass controller's static pressure setpoint
high enough to provide the demand but low enough to maintain reasonable noise levels. The bypass
controller maintains static pressure by controlling a damper or a supply fan VFD. You need the following data
to set the static pressure:
• The air source's design maximum airflow in CFM (manufacturer's data)
•
The system's design external static pressure (inches or water). This is the amount of static pressure that
the air source is designed to deliver at its maximum design airflow in CFM (supplied by the mechanical
design engineer).
• The maximum cooling or heating (whichever is greater) CFM requirements for all zones connected to the
air source
NOTE The air source fan must have been tested and certified that it can deliver the above requirements.
The sum of the maximum CFM requirements of all zones will generally exceed the air source's maximum CFM
rating by 10 to 20%. This is by design and based on a factor known as diversity. It works on the basis that
under normal design heating and cooling conditions, not every zone will be 100% open. Knowing this, you will
need to force open only zones whose sum CFM is equal to the unit design CFM. With the bypass damper fully
closed (0%) or supply fan VFD at 100%, the bypass controller's static pressure should be the controlling
setpoint.
To set the static pressure:
Starting with zone furthest from the air source and working towards it, add up the maximum design CFM
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airflow of the zones until the sum equals the air source's design CFM (+/-5%). Note each zone that you
included.
For each zone noted in step 1, go to Properties > Equipment > Configuration > Service Configuration >
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Pressure Dependent Control > Details tab. Click Cool Max or Heat Max (whichever has the highest
design max airflow) to force the damper to its maximum open position.
In the tree, select the Bypass controller, then go to Properties > Equipment > Status. Note the Static
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Pressure value, then go to Unit Configuration > Bypass Control > Details tab.
If Damper Position is 0% or VFD Output is 100%, enter the static pressure in the Duct Static
○
Pressure Setpoint field.
If the Damper Position is not 0% or VFD Output is not 100%, enter the static pressure +.1" in the
○
Duct Static Pressure Setpoint field. Wait 1–2 minutes, then verify that the Damper Position is 0% or
VFD Output is 100%. If not, repeat the process, adding .05" to the previous Duct Static Pressure
Setpoint until the Damper Position is 0% or VFD Output is 100%.
38 VVT Zone Controller