73
contact closure. Multiple smoke control inputs, sensed by the
control will force the unit into a Fire Shutdown mode.
FIRE SMOKE INPUTS — These discrete inputs can be
found on the local display under Inputs
→
FIRE.
Fire Shutdown Mode — This mode will cause an immediate
and complete shutdown of the unit.
Pressurization Mode — This mode attempts to raise the pres-
sure of a space to prevent smoke infiltration from an adjacent
space. Opening the economizer (thereby closing the return air
damper), shutting down power exhaust and turning the indoor
fan on will increase pressure in the space.
Evacuation Mode — This mode attempts to lower the pres-
sure of the space to prevent infiltrating an adjacent space with
its smoke. Closing the economizer (thereby opening the return-
air damper), turning on the power exhaust and shutting down
the indoor fan decrease pressure in the space.
Smoke Purge Mode — This mode attempts to draw out
smoke from the space after the emergency condition. Opening
the economizer (thereby closing the return-air damper), turning
on both the power exhaust and indoor fan will evacuate smoke
and bring in fresh air.
AIRFLOW CONTROL DURING THE FIRE/SMOKE
MODES — All non-smoke related control outputs will get
shut down in the fire/smoke modes. Those related to airflow
will be controlled as explained below. The following matrix
specifies all actions the control shall undertake when each
mode occurs (outputs are forced internally with CCN priority
number 1 - “Fire”):
*“FSO” refers to the supply and exhaust VFD/IGV fire speed over-
ride configurable speed.
RELEVANT ITEMS:
The economizer’s commanded output can be found in
Outputs
→
ECON
→
ECN.C.
The configurable fire speed override for supply fan VFD/IGV
is in Configuration
→
SP
→
SP.FS.
The supply fan relay’s commanded output can be found in
Outputs
→
FANS
→
S.FAN.
The supply fan VFD’s commanded speed can be found in
Outputs
→
FANS
→
S.VFD.
The inlet guide vane’s commanded position can be found in
Outputs
→
ACTU
→
IGV.C.
The configurable fire speed override for exhaust VFD/actuator
is in Configuration
→
BP
→
B.V.A
→
BP.FS.
The exhaust fan VFD’s commanded speed can be found in
Outputs
→
FANS
→
E.VFD.
The power exhaust actuators command positions can be found
in Outputs
→
ACTU
→
BPx.C.
Indoor Air Quality Control — The indoor air quality
(IAQ) function will admit fresh air into the space whenever
space air quality sensors detect high levels of CO2.
When a space or return air CO2 sensor is connected to the
unit control, the unit’s IAQ routine allows a demand-based
control for ventilation air quantity, by providing a modulating
outside air damper position that is proportional to CO2 level.
The ventilation damper position is varied between a minimum
ventilation level (based on internal sources of contaminants
and CO2 levels other than from the effect of people) and the
maximum design ventilation level (determined at maximum
populated status in the building). Demand Control Ventilation
(DCV) is also available when the ComfortLink™ unit is con-
nected to a CCN system using ComfortID™ terminal controls.
This function also provides alternative control methods for
controlling the amount of ventilation air being admitted,
including fixed outdoor air ventilation rates (measured as cfm),
external discrete sensor switch input and externally generated
proportional signal controls.
The IAQ function requires the installation of the factory-
option economizer system. The DCV sequences also require
the connection of accessory (or field-supplied) space or return
air CO2 sensors. Fixed cfm rate control requires the factory-
installed outdoor air cfm option. External control of the
ventilation position requires supplemental devices, including a
4 to 20 mA signal, a 10-kilo-ohm potentiometer, or a discrete
switch input, depending on the method selected. Outside air
CO2 levels may also be monitored directly and high CO2
economizer restriction applied when an outdoor air CO2 sensor
is connected. (The outdoor CO2 sensor connection requires
installation of the controls expansion module [CEM].)
The ComfortLink controls have the capability of DCV us-
ing an IAQ sensor. The indoor air quality (IAQ) is measured
using a CO2 sensor whose measurements are displayed in parts
per million (ppm). The IAQ sensor can be field-installed in the
return duct. There is also an accessory space IAQ sensor that
can be installed directly in the occupied space. The sensor must
provide a 4 to 20 mA output signal and must include its own
24-v supply. The sensor connects to TB202 terminals 11 and
12. Be sure to leave the 182-ohm resistor in place on terminals
11 and 12.
OPERATION — The unit’s indoor air quality algorithm mod-
ulates the position of the economizer damper between two user
configurations depending upon the relationship between the
IAQ and the outdoor air quality (OAQ). Both of these values
can be read at the Inputs
→
AIR.Q submenu. The lower of these
two configurable positions is referred to as the IAQ Demand
Vent Min Position (IAQ.M), while the higher is referred to as
Economizer Minimum Position (EC.MN). The IAQ.M should
be set to an economizer position that brings in enough fresh air
to remove contaminants and CO2 generated by sources other
than people. The EC.MN value should be set to an economizer
position that brings in enough fresh air to remove contaminants
and CO2 generated by all sources including people. The
EC.MN value is the design value for maximum occupancy.
The logic that is used to control the dampers in response to
IAQ conditions is shown in Fig. 11. The ComfortLink controls
will begin to open the damper from the IAQ.M position when
the IAQ level begins to exceed the OAQ level by a config-
urable amount, which is referred to as Differential Air Quality
Low Limit (DAQ.L).
If OAQ is not being measured, OAQ can be manually con-
figured. It should be set at around 400 to 450 ppm or measured
with a handheld sensor during the commissioning of the unit.
The OAQ reference level can be set using the OAQ Reference
Set Point (OAQ.U). When the differential between IAQ and
OAQ reaches the configurable Diff. Air Quality Hi Limit
(DAQ.H), then the economizer position will be EC.MN.
When the IAQ–OAQ differential is between DAQ.L and
DAQ.H, the control will modulate the damper between IAQ.M
and EC.MN as shown in Fig. 11. The relationship is a linear
relationship but other non-linear options can be used. The
ITEM EXPANSION RANGE CCN
POINT
WRITE
STATUS
FIRE FIRE-SMOKE INPUTS
FSD Fire Shutdown Input ALRM/NORM FSD forcible
PRES Pressurization Input ALRM/NORM PRES forcible
EVAC Evacuation Input ALRM/NORM EVAC forcible
PURG Smoke Purge Input ALRM/NORM PURG forcible
DEVICE PRESSURIZATION PURGE EVACUATION FIRE
SHUTDOWN
Economizer 100% 100% 0% 0%
Indoor Fan —
VFD/IGV ON/FSO* ON/FSO* OFF OFF
Power Exhaust
VFD-Actuator OFF ON/FSO* ON/FSO* OFF
Heat Interlock
Relay ON ON OFF OFF