Rtu (Roof Top Unit) - KMC Controls FlexStat Application Manual

RTU (Roof Top Unit)

Fan Control
The fan follows the base sequence for fan operation as listed in the
Stat (All Models) Common Features
modifications.
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 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 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 off 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 deadband AND the first stage of
heating has been off for at least the minimum off time, the first stage of
heating will be energized. If the space temp further drops below the ac-
tive heating setpoint minus the deadband AND the first stage of heating
has been energized for at least the stage delay AND the second stage of
heating has been off for at least the minimum off time, the second stage
of heating will be energized. Upon rise in temperature above the ac-
tive heating setpoint minus one half the deadband, the second stage of
heating will be de-energized. Upon further rise in temperature above the
active heating setpoint, the first stage of heating will be de-energized.
In the cooling mode, if the space temp rises above the active cooling
setpoint plus one half the deadband AND the first stage of cooling has
been off for at least the minimum off time, the first stage of cooling will
be energized. If the space temp further rises above the active cooling
BAC-1xx36/1xxx36 Series (3 Relays and 6 Analog Outputs) Section
section above with the following
setpoint plus the deadband AND the first stage of cooling has been en-
ergized for at least the stage delay AND the second stage of cooling has
been off for at least the minimum off time, the second stage of cooling
will be energized. Upon decrease in space temp below the active cooling
Flex-
setpoint plus one half the deadband, the second stage of cooling shall
be de-energized. Upon further decrease in space temp below the active
cooling setpoint, the first 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 off 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 configured for the modulating economizer
option, the above economizer sequence is followed. If the application is
configured 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 dehumidification mode, both stages of cooling
are energized after they have been off for at least the minimum off time.
Heating stages then follow their normal sequence to maintain the active
heating setpoint.
45 Application Guide L