Viconics VBZS Application Guide - Manual (Page 15)

15
- The selected zone dampers minimum position has a direct impact on the temperature stability for
certain zones. Having a minimum position selected may produce an over cooling or over heating
effect. This effect is created when the primary air temperature is in the inverse mode than that
which the zone currently requires. An example of this is when an internal zone is requesting
cooling during winter while the RTU is supplying hot air for the external zones.
Adjusting the minimum position of a zone damper is mandatory by NA standards. It is however the
choice of the installer to decide if in some cases removing it or lowering it to a value below
standard may solves a system design issue. A good example of this would be an internal zone with
a grossly oversized VAV unit.
How to test and balance the Minimum, Maximum and Heat Flow values:
Balancing Minimum Air Flow
1. Be sure local system heating is allowed by setting the outdoor heating lockout value at the RTU
controller (H Lock)
2. Be sure the system is currently in heating mode. As viewed locally at the RTU controller by pressing
the manual scroll button and displaying the local Zone Sequence = Heat message prompt.
3. Be sure that the master voting zones are calling for heating by setting the appropriate set points
accordingly.
4. Set the currently balanced controller set point to its minimum value. An example of this would be
60F or when the set point is at least 7-8 F lower than the current room temperature. This will drive
the VAV zone to its minimum value.
5. Set the (Min Pos) configuration parameter to the desired value as required by balancing.
Balancing Maximum Air Flow
1. Be sure local system heating is allowed by setting the outdoor heating lockout value at the RTU
controller (H Lock)
2. Be sure the system is currently in heating mode. As viewed locally at the RTU controller by pressing
the manual scroll button and displaying the local Zone Sequence = Heat message prompt.
3. Be sure that the master voting zones are calling for heating by setting the appropriate set points
accordingly.
4. Set the currently balanced controller set point to its minimum value. An example of this would be 60F
or when the set point is at least 7-8 F lower than the current room temperature. This will drive the VAV
zone to its minimum value.
5. Set the (Max Pos) configuration parameter to the desired value as required by balancing.
Balancing Maximum Heat Flow
1. Be sure local system cooling is allowed by setting the outdoor cooling lockout value at the RTU
controller (C Lock).
2. Be sure local reheat is allowed by appropriately setting the outdoor reheat lockout value at the Zone
controller (AO2 OALK or BO5 OALK).
3. Be sure the system is currently in cooling mode. As viewed locally at the RTU controller by pressing
the manual scroll button and displaying the local Zone Sequence = Cool message prompt.
4. Be sure that the master voting zones are calling for cooling by setting the appropriate set points
accordingly.
5. Set the currently balanced controller set point to its minimum value. An example of this would be 60F
or when the set point is at least 7-8 F lower than the current room temperature. This will drive the VAV
zone to its minimum value.
6. Set the (MaxHTPos) configuration parameter to the desired value as required by balancing.