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SCXG-SVX01B-EN 85
sequence of
operation
is reached. Next a 60 minute timer
begins. If the building load reaches the
MWU ventilation setpoint, or the 60
minutes expire, whichever is first, the
airside economizer will control to the
minimum position. MWU will end when
the zone temperature rises above the
MWU terminate setpoint.
Timed Override Activation - ICS™
This function is operational whenever the
unit’s RTM module is used as the zone
temperature sensor source, which can be
set at the HI panel. When this function is
initiated by the push of the override
button on the zone sensor, the unit will
switch to the occupied mode. Unit
operation (occupied mode) during timed
override is terminated by a signal from
Tracer.
Timed Override Activation - Non-ICS
This function is active whenever the unit’s
RTM module board is selected as the
zone temperature source, which can be
set at the human interface panel. When
this function is initiated by the push of the
override button on the zone sensor, the
unit will switch to the occupied mode.
Automatic cancellation of the timed
override mode occurs after three hours
of operation.
VAV Drive Max Output
This is a single-pole, double-throw relay
rated at a maximum voltage of 24 vac,
two amps max. The relay contacts of this
relay switch when the unit goes from the
occupied mode to the unoccupied mode
by means of the unoccupied binary input,
night setback zone sensor, or Tracer
Summit. The contacts will stay switched
during the unoccupied and morning
warmup mode. They will return to the
position shown on the unit wiring
diagram when the unit returns to the
occupied mode. The intent of this binary
output is to signal the VAV boxes or other
terminal devices to go to a full open
airflow position.
For units without volume control entering
unoccupied mode, the following se-
quence will occur:
• The occupied/unoccupied relay ener-
gizes and the economizer option fully
closes.
• The fan mode is set to auto and the unit
will control to the unoccupied zone
temperature setpoints.
With MWU enabled at the HI, if the zone
temperature is below the MWU setpoint,
the unit enters the MWU mode.
Morning Warmup
This feature can be enabled at the HI, and
can be used with factory or field-installed
heat. If MWU is not required disable the
function in the setup menu at the HI.
MWU transitions the zone from
unoccupied to occupied. It will heat until
the MWU setpoint is met. The unit is then
released to occupied mode. Supply duct
static pressure is maintained during this
sequence. MWU can be set (at the HI) to
function as either full or cycling capacity.
Full Capacity Morning Warmup (MWU)
Full capacity morning warmup uses full
heating capacity to heat the zone as
quickly as possible. Full heating capacity
is provided until the morning warmup
setpoint is met. At this point, the unit is
released to daytime mode.
Cycling Capacity Morning Warmup
(MWU)
Cycling capacity morning warmup
provides a more gradual heating to
overcome “building sink” as the zone is
heated. Normal zone temperature control
with varying capacity is used to raise the
zone temperature to the MWU zone
temperature setpoint. This method of
warmup is used to overcome the
“building sink” effect.
Reference Figure O-SO-1 on page 73 for
a pictorial explanation of the cycling
MWU sequence. Cycling capacity MWU
will heat until MWU temperature setpoint
Operation