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APPENDIX E — MODE SELECTION PROCESS
The following section is to be used in conjunction with
Fig. 4 on page 43. To help determine why the unit controls are
in a certain mode, the programming logic is provided below.
The software will proceed, step by step, until a mode is
reached. If an “If” statement is true, then that mode will be en-
tered. The “Else” statement refers to other possible choices.
If the System Mode is OFF:
{
If the fire shut down input (Inputs
→
FIRE
→
FSD)
is in “alarm”:
HVAC mode: ("Fire Shut Down ") OFF
Else
HVAC mode: ("Disabled ") OFF
}
Else If: The rooftop is not in “factory test” and a fire
smoke-control mode is “alarming”:
{
If the pressurization input (Inputs
→
FIRE
→
PRES)
is in “alarm”:
HVAC mode: ("Pressurization ")
Else If the evacuation input (Inputs
→
FIRE
→
EVAC)
is in “alarm”:
HVAC mode: ("Evacuation ")
Else If the smoke purge input (Inputs
→
FIRE
→
PURG)
is in “alarm”:
HVAC mode: ("Smoke Purge ")
}
Else If: Someone changed the machine’s
control type (Configuration
→
UNIT
→
C.TYP) during
run time, a 15 second delay is called out:
{
HVAC mode: ("Disabled ") OFF
}
Else If: The System Mode is TEST:
{
HVAC mode: ("Test ")
}
Else If: The “soft stop” command (Service Test
→
S.STP)
is forced to YES:
{
HVAC mode: ("SoftStop Request")
}
Else If: The remote switch config (Configuration
→
UNIT
→
RM.CF)=2; “start/stop”, and the remote
input state (Inputs
→
GEN.I
→
REMT)=ON:
{
HVAC mode: ("Rem. Sw. Disable") OFF
}
Else If: Configured for hydronic heat (Configuration
→
HEAT
→
HT.CF=4) or configured for dehumidification
with modulating valve reheat (Configuration
→
DEHU
→
D.SEL=1) and the freeze stat switch trips
(Inputs
→
GEN.I
→
FRZ.S = ALRM)
{
HVAC mode: ("Freeze Stat Trip")
}
Else If: Configured for static pressure control
(Configuration
→
SP
→
SP.CF = 1,2) and the static
pressure sensor (Pressures
→
AIR.P
→
SP) fails:
{
HVAC mode: ("Static Pres.Fail") OFF
}
Else If: Configured for supply fan status monitoring
(Configuration
→
UNIT
→
SFS.M = 1,2) and
configured to shut the unit down on fan status fail
(Configuration
→
UNIT
→
SFS.S = YES)
{
HVAC mode: ("Fan Status Fail ") OFF
Else If: Configured for return fan tracking
(Configuration
→
BP
→
BP.CF = 5) and there is a
plenum pressure switch error
HVAC mode: ("Plen.Press.Fail ") OFF
}
Else If: The unit is just waking up from a power reset
{
HVAC mode: ("Starting Up ") OFF
}
Else If: A compressor is diagnosed as being “Stuck On”
{
HVAC mode: ("Comp. Stuck On ")
Else The control is free to select the normal heating/
cooling HVAC modes:
{
HVAC mode: ("Off ")
— The unit is off and no operating modes are active.
HVAC mode: ("Tempering Vent ")
— The economizer is at minimum vent position but
the supply air temperature has dropped below the
tempering vent set point. Gas or hydronic heat is
used to temper the ventilation air.
HVAC mode: ("Tempering LoCool")
— The economizer is at minimum vent position but
the combination of the outside-air temperature and
the economizer position has dropped the supply-air
temperature below the tempering cool set point.
Gas or hydronic heat is used to temper the
ventilation air.
HVAC mode: ("Tempering HiCool")
— The economizer is at minimum vent position but
the combination of the outside air temperature and
the economizer position has dropped the supply air
temperature below the tempering cool set point.
Gas or hydronic heat is used to temper the
ventilation air.
HVAC mode: ("Re-Heat ")
— The unit is operating in dehumidification with a
reheat device.
HVAC mode: ("Dehumidification")
— The unit is operating in the Dehumidification
mode.
