KMC Controls FlexStat Application Manual page 42

active cooling setpoint plus one half the deadband AND the first
stage of compressor has been off for at least the minimum off
time, the first stage of compressor will be energized. If the space
temp further rises above the active cooling setpoint plus the
deadband AND the first stage of compressor has been energized
for at least the stage delay AND the second stage of compressor
has been off for at least the minimum off time, the second stage
of compressor will be energized. Upon decrease in space temp
below the active cooling setpoint plus one half the deadband, the
second stage of compressor shall be de-energized. Upon further
decrease in space temp below the active cooling setpoint, the first
stage of compressor shall be de-energized.
If at any time there is a fan failure alarm or low limit alarm, all com-
pressor stages are de-energized.
Auxiliary/Emergency Heat
The heat pump application can be configured with auxiliary heat in
three methods: no auxiliary heat, auxiliary heat with outside air temp
compressor lockout, and auxiliary heat without outside air temp com-
pressor lockout.
If the unit is configured for auxiliary heat without compressor lock-
out, the auxiliary heat and emergency heat function as third and fourth
stages of heat. If the space temperature drops below the active heating
setpoint minus 1.5 times the deadband and remains below that tem-
perature for the Auxiliary Heat Delay (adjustable), the auxiliary heat is
energized. If the space temperature further falls below the active heating
setpoint minus 2 times deadband and the auxiliary heat is energized, the
emergency heat is then energized. If the space temperature rises above
the active heating setpoint minus 1.5 times deadband, the emergency
heat is de-energized. If the space temp further rises above the active
heating setpoint minus the deadband, the auxiliary heat is de-energized.
If the heat pump application is configured for auxiliary heat with com-
pressor lockout, a compressor lockout mode is enabled if the outside air
BAC-1xx63/1xxx63 Series (6 Relays and 3 Analog Outputs) Section
temperature drops 1.0° F (0.56° C) below the Compressor OAT Low Limit.
The compressor lockout mode is disabled if the outside air temperature
rises 1.0° F (0.56° C) above the Compressor OAT Low Limit. If the com-
pressor lockout mode is disabled, the auxiliary and emergency heat func-
tion as described above. If the compressor lockout mode is enabled, all
stages of compressor are de-energized and the auxiliary and emergency
heat function as described above but without the Auxiliary Heat Delay.
If the System Mode is set to "Emer Ht," the compressors are locked out
and the auxiliary and emergency heat stage operate as follows:
If the space temp drops below the active heating setpoint minus one half
the deadband, the auxiliary heat is energized. If the space temp further
falls below the active heating setpoint minus the deadband AND the
auxiliary heat has been energized for at least the stage delay, the emer-
gency heat is energized. Upon rise in temperature above the active heat-
ing setpoint minus one half the deadband, the emergency heat will be
de-energized. Upon further rise in temperature above the active heating
setpoint, the auxiliary heat will be de-energized.
Any time there is a fan failure alarm or low limit alarm, auxiliary and
emergency heating are de-energized.
Economizer Control
If the HPU application is configured for the economizer option, the base
economizer sequence described in the Common Features section is followed.
Dehumidification
Upon activation of the dehumidification mode, configured stages of
compressor are energized after they have been off for at least the mini-
mum off time. The reversing valve is set to the cooling mode based on
the reversing valve configuration. Auxiliary and emergency heating
stages then follow their normal sequence to maintain the active heating
setpoint.
42 Application Guide L