Product Overview

BAC-1xx36/1xxx36 Series (3 Relays and 6 Analog Outputs) Section 61 Application Guide S
Sequence of Operation (BAC-1xx36/1xxx36)
NOTE: This information reects rmware version R2.0.0.13 or later
(but specications are subject to change).
BAC-1xx36/1xxx36 Common Features
For common features, see FlexStat (All Models) Common Features on
page 42.
BAC-1xx36/1xxx36 Series Applications
AHU (Air Handling Unit)
Fan Control
The fan follows the base sequence for fan operation as listed in the Flex-
Stat (All Models) Common Features section with the following modi-
cations.
Modulating/One Stage—The fan will start if the space temp rises above
the active cooling setpoint plus the cooling proportional band and will
stop if the space temp drops below the active cooling setpoint. If the
space temp drops below the active heating setpoint minus the heating
proportional band, the fan will start and will stop when the fan rises
above the active heating setpoint.
Two Stages—The fan will start if the space temp rises above the active
cooling setpoint plus one half the cooling proportional band and will
stop if the space temp drops below the active cooling setpoint. If the
space temp drops below the active heating setpoint minus one half the
heating proportional band, the fan will start and will stop when the fan
rises above the active heating setpoint. This will allow one of the two
stages of heating or cooling to run by itself before staging on the second
stage.
Fan o delays apply as described in Staged Heating and Cooling.
Fan Speed Control
Fan speed is controlled by the Fan Control Type (Speeds) seing. If the
fan control type is set to “constant,” then the fan speed output is not
used.
If the fan control type is set to “variable,” then the following sequence
applies. When the fan runs, whether in “Auto” or “On” mode, the fan
speed is determined by the Output Speed seing. If the Output Speed
seing is set to “xed,” then any time the fan is called for, it will run at
the speed designated by the Fixed Speed seing. This allows for the fan
speed to be manually set by a balancer.
If the Output Speed is set to “Auto,” then the speed the fan runs is de-
termined by both the fan mode (auto/on) and the heating or cooling PI
loops.
If the current fan mode is set to “auto,” the fan cycles at 100% speed. If
the current fan mode is set to “on,” the fan is started at minimum speed
upon call for heating or cooling and remains there until the active heat-
ing or cooling PI loop reaches 60%. Once above 60%, the fan is modulat-
ed up to 100% based on the upper 40% of the heating or cooling PI loop,
whichever is active. The fan slows down in the reverse sequence. This
operation allows the AHU to aempt to maintain space temperature
setpoint using the valve at minimum fan speed. If space temp setpoint
cannot be maintained at minimum speed, increasing the fan speed will
allow more heat transfer to/from the coil.
Valve Control (If Configured)
The method of controlling the heating and cooling valves is based on the
fan conguration:
• If the fan mode for a particular occupancy mode is set to con-
stant or “On,” the valves function in a modulating fashion.
Actual response may vary slightly due to PI action of the control
loops, but generally the heating valve will start to open as the
space temperature drops below the active heating setpoint and
modulate to fully open when space temperature reaches active
heating setpoint minus heating proportional band. Likewise, the
cooling valve will generally begin opening as the space tempera-
ture rises above the active cooling setpoint and be fully open by
the time the space temp reaches the active cooling setpoint plus
cooling proportional band, modulating linearly in between.