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APPENDIX C — VAV ZONE CONTROLLER - SUBMITTAL EXAMPLE (CONT)
E. Unoccupied time period: (reheat)
When the unoccupied period is reached, the user-defined
occupied heating set point is reset downward to a user-
defined unoccupied heating set point. The damper will
operate in the same manner (as per B) during the unoc-
cupied period. The hot water valve will operate as
required to satisfy the heating load.
F. Unoccupied time period: (heating)
When the unoccupied period is reached, the user-defined
occupied heating set point is reset downward to a user-
defined unoccupied heating set point. The damper will
operate in the same manner (as per C) during the unoc-
cupied period, if the air source provides heat. The hot
water valve will operate to supplement the primary air
heat (if required).
G. Morning warm-up: (if not configured to provide constant
volume heating)
Upon receiving a morning warm-up signal generated by
the air source equipped with BACnet controls, the damper
will go to the maximum heating airflow set point if the
zone temperature is below the occupied heating set point
at 6. This allows the warm primary air to be delivered
to the zone. As the zone temperature rises above the
occupied heating set point, the damper will move toward
the minimum heating airflow set point at 4'. The hot
water valve will operate to supplement the primary air
heat (if required) and controlled so as not to exceed the
maximum discharge temperature limit.
H. Demand controlled ventilation (option):
Whenever the zone is occupied and the air source is not
heating (determined by receiving a cooling signal from the
air source equipped with BACnet controls or a primary air
temperature sensor is installed to detect the air source is
operating in the Cooling mode), the control will monitor
a CO
sensor (optional) and determine if ventilation is
2
adequate. The zone CO
lation set point. If the CO
(insufficient ventilation), the airflow set point is increased
appropriately to maintain proper ventilation. Should the
zone's temperature fall, reheat will operate to maintain
the zone's temperature midway between the heating
and cooling set points. Should the zone's temperature
fall below the heating set point, the control will suspend
ventilation override until the zone's temperature recovers
(reheat will operate as per B).
J. Humidity control (option):
Whenever the zone is occupied and the air source is
LEGEND
NTFC—Nighttime Free Cooling
Air Source Supplying Heated Air
Air Source Supplying Cooled Air
Figure 2 - Sequence of Operation for Single Duct Air Terminal with Two-Position Hot Water or Steam Heat
JOB NAME
BUYER
level is compared to the venti-
2
level is above the set point
2
% AIRFLOW
100%
MAX COOL LIMIT
(DAMPER OVERRIDE
PRESSURIZATION
MODE)
MAX HEAT LIMIT
FULL HEATING
REHEAT LIMIT
MIN HEAT LIMIT
MIN COOL LIMIT
<
>
0%
DAMPER
COOL
OVERRIDE-
EVACUATION
MODE
JOB NUMBER
BUYER #
cooling (determined by receiving a cooling signal from
the air source equipped with BACnet controls or a primary
air temperature sensor is installed to detect the air source
is operating in the Cooling mode), the control will monitor
a relative humidity (rh) sensor (optional) and determine
if the zone's rh is above the humidity set point. If the rh
level is above the rh set point, the airflow control point is
increased to displace the humid air in the space with air
from the primary air source (which has a lower dew point).
To ensure non-simultaneous operation of both heating
and cooling, should the increased airflow cause the
zone's temperature to fall below the heating set point, the
control will suspend the airflow override. Reheat will be
enabled to maintain the zone's heating set point (reheat
will operate as per B). The airflow override will resume
when the zone's temperature recovers and be disabled
once the zone's rh level falls below the zone's rh set point.
K. Damper override:
The damper override function is energized through the
use of a field-supplied smoke control panel connected to
the air source equipped with BACnet controls. The smoke
control panel and installation must be in accordance with
UL864 and local codes. The damper override function
overrides the airflow setting used by the logic. It will cause
the terminal to provide the configured maximum cooling
airflow when the air source is in the Pressurization mode,
and to fully close the damper when the air source is in the
Evacuation mode.
M. Nighttime free cooling:
The logic calculates nighttime free cooling (NTFC) tem-
perature set point halfway between the occupied heating
and occupied cooling temperature set points. Upon
receiving a NTFC signal generated by the air source
equipped with BACnet controls (or a primary air temperature
sensor is installed to detect the air source is operating in
the NTFC mode), the damper will throttle between the
maximum and minimum cooling airflow set points as
required to maintain the zone's NTFC temperature set point.
N. Primary air source shuts off:
1. The damper will fully close and the control will
recalibrate the airflow transducer.
2. If the primary air source remains off (no primary air),
the damper will be repositioned to at least 50% open
to allow the air source to restart properly.
TWO-POSITION
FULL COOLING
HOT WATER HEAT
OFF
ON
DEADBAND
NTFC
OCCUPIED
OCCUPIED
SETPOINT
COOLING
HEATING &
MORNING
SPACE TEMPERATURE
WARM-UP
SETPOINT
LOCATION
SHEET
46
WARM
PAGE NUMBER
DRAWING NUMBER
2 OF 3
3 5 E D - 4 2 4 3
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