Product Overview

BAC-1xx63/1xxx63 Series (6 Relays and 3 Analog Outputs) Section 56 Application Guide S
RTU (Roof Top Unit)
Fan Control
The fan follows the base sequence for fan operation as listed in the Flex-
Stat (All Models) Common Features section above with the following
modications.
If the fan mode is set to “Auto,” 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 set-
point. If the space temp drops below the active heating setpoint minus
one half the heating proportional band, the fan will start and stop when
the fan rises above the active heating setpoint. This will allow only one
stage of heating or cooling to run if necessary.
Fan o delays apply as previously described.
Heating/Cooling Staging
In the heating mode, if the space temperature drops below the active
heating setpoint minus one half the heating proportional band, the rst
stage of heating will be energized. If the space temp further drops below
the active heating setpoint minus the heating proportional band AND
the rst stage of heating has been energized for at least the stage delay,
the second stage of heating will be energized. Upon rise in temperature
above the active heating setpoint minus one half the heating proportion-
al band, the second stage of heating will be de-energized. Upon further
rise in temperature above the active heating setpoint, the rst stage of
heating will be de-energized.
In the cooling mode, if the space temp rises above the active cooling set-
point plus one half the cooling proportional band AND the rst stage of
cooling has been o for at least the minimum o time, the rst stage of
cooling will be energized. If the space temp further rises above the active
cooling setpoint plus the cooling proportional band AND the rst stage
of cooling has been energized for at least the stage delay AND the sec-
ond stage of cooling has been o for at least the minimum o time, the
second stage of cooling will be energized. Upon decrease in space temp
below the active cooling setpoint plus one half the cooling proportional
band, the second stage of cooling shall be de-energized. Upon further
decrease in space temp below the active cooling setpoint, the rst stage
of cooing shall be de-energized.
If the economizer option is set to modulating economizer and the econo-
mizer mode is enabled, the stages of cooling will be held o until the
outside air damper is 100% open. When the outside air damper is fully
open, normal staging of cooling is allowed. If the economizer option is
set to “Econ Dis/En” and the economizer mode is enabled, cooling is al-
lowed to stage normally.
If at any time there is a fan failure alarm or a low limit alarm, all
stages of heating and cooling are stopped at priority 5, bypassing any
minimum on times (minimum on times added by others, not part of the
base sequence).
Economizer Control
If the RTU application is congured for the modulating economizer
option, the above economizer sequence is followed. If the application is
congured for econ disable/enable, the economizer mode is determined
as above. Any time the econ mode is enabled, the econ dis/en output is
energized. If the econ mode is disabled, the econ dis/en output is de-
energized.
Dehumidification
Upon activation of the dehumidication mode, both stages of cooling
are energized after they have been o for at least the minimum o time.
Heating stages then follow their normal sequence to maintain the active
heating setpoint.