BAC-1xx63/1xxx63 Series (6 Relays and 3 Analog Outputs) Section
35
Application Guide L
OAT
Econ Loop “P” factor
65
15
53
15
50
15
45
22.5
40
30
30
30
During occupied mode, the mixed air temp setpoint is determined based
on a reset schedule. If the space temperature is at or below the active
cooling setpoint, the mixed air temp setpoint is MAT Max Temp (68.0°
F or 20.0° C). If the space temperature is 2.0° F (1.1° C) above the active
cooling setpoint, the mixed air temp setpoint will be MAT Min Temp
(53.0° F or 11.7° C). The mixed air setpoint will vary linearly in between.
MAT Min Temp and MAT Max Temp are adjustable from the U/I.
During unoccupied mode, if the space temp exceeds the cooling setback
setpoint by deadband and the econ mode is enabled, the outside air
damper shall open as called for by the mixed air temp loop. The outside
air damper shall modulate to maintain MAT Min (53.0° F or 11.7° C) un-
til the space temp reaches the cooling setback setpoint, at which point it
shall close. If at any time during unoccupied mode the economizer mode
is disabled based on OAT, the outside air damper will close.
If the system mode is set to “heating” during occupied mode, the
damper will open to minimum position when the fan is on. If the system
mode is set to “heating” during unoccupied mode or is set to “off” in
any occupancy mode, the outside damper will close.
If at any time there
is a fan alarm, the outside air damper shall shut.
If the mixed air temp drops below the low limit alarm temp, a low
limit alarm is generated and the outside air damper will close.
Other
safety actions are taken and described in their respective sections below.
DCV (Demand Controlled Ventilation)—General Information
NOTE: See also
CO2 Sensors and DCV on page 16
.
In addition to the Economizer option, BAC-12xxxx/13xxxx/14xxxx
models have the Demand Control Ventilation (DCV) option available.
DCV combines several options and modes into efficiently controlling the
outside air damper . DCV is enabled by setting DCV to one of the three
configurations.
The various Outside Air (OA) % settings that are available are the per-
centage that the OA damper is open and not the percentage of OA flow.
These settings should be measured and set accordingly.
The controller is designed to operate without an outside CO
2
sensor us-
ing a reference
CO2 Base
level (400 ppm default). This setting is adjust-
able from the U/I and should be set to the local average outdoor CO
2
level. If an outdoor CO
2
reference is desired, a spare input on the Flex-
Stat can be used and mapped to AV60. This should be done at priority 8
or higher (higher priority = lower number).
The three types of DCV configurations available are:
• BASIC—Provides simple DCV, modulating the outside air damper in
direct response to the current CO
2
level with respect to its setpoint.
Basic DCV is much more energy efficient than no DCV at all, while
maintaining adequate IAQ (Indoor Air Quality). It is the easiest DCV
method to configure. However, where VOCs, radon, or other pol-
lutants become excessive during unoccupied times (with no venti-
lation), the FlexStat’s Standard or Advanced DCV configuration is
recommended.
• STANDARD—When the BAC-1
3
xxxx settings are properly config-
ured, complies with
CA Title 24, Section 121(c)
. This would also
apply to a properly configured BAC-1
2
xxxx with a remote SAE-10xx
CO
2
sensor. Standard DCV, under most conditions, is somewhat less
energy efficient than Basic, but it enhances IAQ.*
*NOTE: The CO
2
sensors in the BAC-1
3
xxxx series FlexStats (as
well as properly configured SAE-10xx CO
2
detectors) have
been certified to comply with CA Title 24, Section 121(c),
as well as sub-paragraph 4.F that specifies accuracy will be
maintained within tolerance for a minimum of 5 years without
recalibration.
See the data sheet for more information.
