33
2. System in the process of shutting down compressors and
waiting for timeguards to expire.
(“Shutting Down ...”)
3. Factory shut down (internal factory control level —
SHUTDOWN).
(“Factory Shut Down”)
4. Unit Stop (software application level variable that acts as
a hard shut down — Service Test
→
STOP).
(“Local Machine Stop”)
5. Fire Shut Down (traumatic fire shutdown condition based
on the Fire Shutdown Input — Inputs
→
FIRE
→
FSD).
(“Fire-Shutdown Mode”)
6. Emergency Stop, which is forced over the CCN through
the Emergency Stop Variable (EMSTOP).
(“CCN Emergency Stop”)
7. Startup delay.
(“Startup delay = 0-900 secs”)
8. Service test ending transition timer.
(“Service Test Ending”)
9. Unexplained internal software failure.
(“Internal Failure”)
System Mode Test
— When the system mode is Test, the con-
trol is limited to the Test mode and is controllable via the local
displays (Scrolling Marquee and Navigator™ display) or
through the factory service test control. The System Test
modes are Factory Test Enabled and Service Test Enabled. See
the Service Test Mode section for details on test control in this
mode.
1. Factory Test mode
(“Factory test enabled”)
2. Service Test mode
(“Service test enabled”)
System Mode Run
— When the system mode is Run, the soft-
ware application in the control is free to run the HVAC control
routines by which cooling, heating, IAQ, etc., is possible. There
are two possible text displays for this mode, one is normal run
mode and the other occurs if one of the following fire-smoke
modes is present: smoke purge, pressurization or evacuation.
1. Normal run time state
(“Unit Operation Enabled”)
2. Fire-Smoke control mode
(“Fire-Smoke Control”)
HVAC MODES (Operating Mode
→
HVAC) — The HVAC
mode is dependant on the system mode to allow it to further
determine the operational state of the rooftop unit. The actual
determination of an HVAC mode is based on a hierarchal
decision making process whereby certain overrides may inter-
fere with normal temperature/humidity control. The decision
making process that determines the HVAC mode is shown in
Fig. 4 and Appendix D.
Each HVAC Mode is described below. The HVAC mode
number is shown in parenthesis after the mode.
HVAC Mode — OFF (8)
— The unit is off and no operating
modes are active.
HVAC Mode — STARTING UP (0)
— The unit is transi-
tioning from the OFF mode to a different mode.
HVAC Mode — SHUTTING DOWN (2)
— The unit is tran-
sitioning from a mode to the OFF mode.
HVAC Mode — DISABLED (1)
— The unit is shut down
due to a software command disable through the Scrolling Mar-
quee, a CCN emergency stop command, a service test end, or a
control-type change delay.
HVAC Mode — SOFTSTOP REQUEST (3)
— The unit is
off due to a soft stop request from the control.
HVAC Mode — REM SW.DISABLE (4)
— The unit is off
due to the remote switch.
HVAC Mode — FAN STATUS FAIL (5)
— The unit is off
due to failure of the fan status switch.
HVAC Mode — COMP.STUCK ON (7)
— The unit is shut
down because there is an indication that a compressor is run-
ning even though it has been commanded off.
HVAC Mode — TEST
(9) — The unit is in the self test mode
which is entered through the Service Test menu.
HVAC Mode — VENT
(13) — This is a normal operation
mode where no heating or cooling is required and outside air is
being delivered to the space to control IAQ levels.
HVAC Mode — HIGH COOL
(15) — This is a normal cool-
ing mode where a high cooling demand is required.
HVAC Mode — LOW COOL
(14) — This is a normal cool-
ing mode where a low cooling demand is required.
HVAC Mode — UNOCC. FREE COOL (18)
— In this
mode the unit will operate in cooling but will be using the
economizer for free cooling. Entering this mode will depend on
the status of the outside air. The unit can be configured for out-
side air changeover, differential dry bulb changeover, outside
air enthalpy changeover, differential enthalpy changeover, or a
custom arrangement of enthalpy/dewpoint and dry bulb. See
the Economizer section for further details.
HVAC Mode — TEMPERING HICOOL
(12) — The econ-
omizer 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. Staged gas heat is used to temper the ventilation air.
HVAC Mode — TEMPERING LOCOOL
(11) — The econ-
omizer 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. Staged gas heat is used to temper the ventilation air.
HVAC Mode — TEMPERING VENT
(10) — The econo-
mizer is at minimum vent position but the supply-air tempera-
ture has dropped below the tempering vent set point. Staged
gas heat is used to temper the ventilation air.
HVAC Mode — LOW HEAT
(16) — The unit will be in low
heating demand mode using either gas or electric heat.
HVAC Mode — HIGH HEAT
(17) — The unit will be in
high heating demand mode using either gas or electric heat.
HVAC Mode — STATIC PRESSURE FAIL (16)
— The unit
is off due to failure of the static pressure sensor.
HVAC Mode — FIRE SHUT DOWN
(19) — The unit has
been stopped due to a fire shutdown input (FSD) or two or
more of the fire control modes, purge, evacuation, or pressur-
ization have been requested simultaneously.
HVAC Mode — PRESSURIZATION
(20) — The unit is in
the special fire pressurization mode where the supply fan is on,
the economizer damper is open and the power exhaust fans are
off. This mode is invoked by the Fire Pressurization (PRES)
input which can be found in the INPUT
→
FIRE sub-menu.
HVAC Mode — EVACUATION
(21) — The unit is in the
special Fire Evacuation mode where the supply fan is off, the
economizer damper is closed and the power exhaust fans are
on. This mode is invoked by the Fire Evacuation (EVAC) input
which can be found in the INPUT
→
FIRE sub-menu.
HVAC Mode — SMOKE PURGE
(22) — The unit is in the
special Fire Purge mode where the supply fan is on, the econo-
mizer damper is open and the power exhaust fans are on. This
mode is invoked by the Fire Evacuation (PURG) input which
can be found in the INPUT
→
FIRE sub-menu.
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