Sequence Of Operation (Bac-1Xx36/1Xxx36); Bac-1Xx36/1Xxx36 Common Features; Bac-1Xx36/1Xxx36 Series Applications; Ahu (Air Handling Unit) - KMC Controls FlexStat Application Manual

Sequence of Operation (BAC-1xx36/1xxx36)

NOTE: This information reflects firmware version R2.0.0.13 or later
(but specifications are subject to change).

BAC-1xx36/1xxx36 Common Features

For common features, see FlexStat (All Models) Common Features on
page 31.

BAC-1xx36/1xxx36 Series Applications

AHU (Air Handling Unit)

Fan Control
The fan follows the base sequence for fan operation as listed in the
Stat (All Models) Common Features
cations.
Modulating/One Stage—The fan will start if the space temp rises above
the active cooling setpoint plus the deadband 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 deadband, 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 deadband 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 deadband, the fan
will start and will stop when the fan rises above the active heating set-
point. This will allow one of the two stages of heating or cooling to run
by itself before staging on the second stage.
Fan off delays apply as described in Staged Heating and Cooling.
Fan Speed Control
Fan speed is controlled by the Fan Control Type (Speeds) setting. If the
fan control type is set to "constant," then the fan speed output is not
used.
BAC-1xx36/1xxx36 Series (3 Relays and 6 Analog Outputs) Section
section with the following modifi-
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 setting. If the Output Speed
setting is set to "fixed," then any time the fan is called for, it will run at
the speed designated by the Fixed Speed setting. 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-
Flex-
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 attempt 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 configuration:
• 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 deadband. Likewise, the cooling valve
will generally begin opening as the space temperature rises
above the active cooling setpoint and be fully open by the time
the space temp reaches the active cooling setpoint plus dead-
band, modulating linearly in between.
50 Application Guide L