42
HVAC Mode — VENT (09) — 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 (10) — This is a normal cool-
ing mode where a high cooling demand is required.
HVAC Mode — LOW COOL (11) — This is a normal cool-
ing mode where a low cooling demand is required.
HVAC Mode — UNOCC. FREE COOL (12) — 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 (13) — 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 or hydronic heat is used to temper the
ventilation air.
HVAC Mode — TEMPERING LOCOOL (14) — 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 or hydronic heat is used to temper the
ventilation air.
HVAC Mode — TEMPERING VENT (15) — 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 or hydronic 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 — FREEZESTAT TRIP (18) — If the Freez-
estat trips, the unit enters the Freezestat Trip HVAC mode. The
supply fan will run, the hydronic heat valve will be wide open,
and the economizer damper will be at minimum.
HVAC Mode — STATIC PRESSURE FAIL (19) — The
unit is off due to failure of the static pressure sensor.
HVAC Mode — PLENUM PRESSURE FAIL (20) — The
unit is off due to a plenum pressure switch trip.
HVAC Mode — FIRE SHUT DOWN (21) — 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 (22) — 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 submenu.
HVAC Mode — EVACUATION (23) — 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 submenu.
HVAC Mode — SMOKE PURGE (24) — 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 submenu.
HVAC Mode — DEHUMIDIFICATION (25) — The unit is
operating in the Dehumidification mode.
HVAC Mode — RE-HEAT (26) — The unit is operating in
Reheat mode.
Unit Configuration Submenu — The UNIT sub-
menu under the Configuration mode of the local display
contains general unit configuration items. This section will
define all of these configurations here for easy reference. The
sub-menu which contains these configurations is located at the
local display under Configuration
→
UNIT. See Table 33.
Machine Control Type (C.TYP) — This configuration de-
fines the technique and control source responsible for selecting
a cooling, heating, or vent mode and in determining the method
by which compressors are staged. The control types are:
•C.TYP = 1 (VAV-RAT) and C.TYP = 2 ( VAV- S PT )
Both of these configurations refer to standard VAV opera-
tion. If the control is occupied, the supply fan is run
continuously and return-air temperature will be used in the
determination of the selection of a cooling mode. VAV-SPT
differs from VAV-RAT only in that during the unoccupied
period, space temperature will be used instead of return-air
temperature to start the fan for 10 minutes to establish an
accurate return-air temperature before the return-air temper-
ature is allowed to call out any mode.
•C.TYP = 3 (TSTAT – MULTI)
This configuration will force the control to monitor the ther-
mostat inputs to make a determination of mode. Unlike
traditional 2-stage thermostat control, the unit is allowed to
use multiple stages of cooling control and perform VAV-
type operation. The control will be able to call out a LOW
COOL or a HIGH COOL mode and maintain a low or high
cool supply air set point.
•C.TYP = 4 (TSTAT- 2 STG)
This configuration will force the control to monitor the ther-
mostat inputs to make a determination of mode and allow
only 2 stages of control for both heating and cooling.
•C.TYP = 5 (SPT – MULTI)
This configuration will force the control to monitor a space
temperature sensor to make a determination of mode.
Unlike traditional 2-stage space temperature control, the
unit is allowed to use multiple stages of cooling control and
perform VAV-type operation. The control will be able to call
out a LOW COOL or a HIGH COOL mode and maintain a
low or high cool supply air set point.
•C.TYP = 6 (SPT- 2 STG)
This configuration will force the control to monitor the
space temperature sensor to make a determination of mode
and allow 2 stages of control for both heating and cooling.