RT-SVF69C-EN
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Sequence of Operation
lists the selectable dry bulb values by
potentiometer setting.
2. Reference Enthalpy - controlling the economizer cycle
by sensing the outdoor air humidity.
lists the
selectable enthalpy values by potentiometer setting. If
the outside air enthalpy value is less than the selected
value, the economizer is allowed to operate.
3. Comparative Enthalpy - By utilizing a humidity sensor
and a temperature sensor in both the return air stream
and the outdoor air stream, the economizer will be able
to establish which conditions are best suited for
maintaining the zone temperature, i.e., indoor
conditions or outdoor conditions.
Off Mode
This mode is set at the zone sensor or by ICS. During this
status, no heating, ventilation, or mechanical cooling is
being performed. When switching the “System” selector
to the “Off” mode from any other mode, any diagnostic
data and diagnostic indication signal will be retained as
long as the system remains in the “Off” status. Switching
the “System” selector from the “Off” mode back to any
other mode of operation will reset all diagnostics.
Heating Operation
Heating operation on units configured with Traditional
Multi-Zone VAV control will utilize two separate control
methodologies based on heating configurations. For all
“Staged” Heating types (Electric and Gas), the unit will
utilize 100% full airflow during all active heating periods
like traditional Constant Volume units. If the unit has
modulating heat, the unit can be made to do discharge
heating with VAV control. This is done by placing by
placing a contact closure across the “Changeover Input”
on the RTAM. During this mode, the unit will heat to the
Supply Air Heating Setpoint ± 3.5°F. During low load or low
airflow conditions the actual temperature swing of the
discharge air will likely be greater.
Zone Temperature - Unoccupied Heating
While a building is in an unoccupied period as designated
by a remote panel with night setback or ICS, the necessary
heating capacity will be controlled to maintain the zone
temperature to within the unoccupied setpoint deadband.
For traditional VAV systems, the VFD will operate at 100%
during this mode. It will be necessary to drive VAV boxes
to their maximum position through ICS programming or
the factory provided VHR relay. For Modulating Gas Heat
units, Full Airflow is not required but can be enabled by
connecting the changeover mode input J5-1 and J5-2 on
the RTAM module. For all Staged Heating types, the
Supply Fan will be controlled at maximum fan speed
during active heating operation as during Occupied
periods.
Gas Heat Control
The ignition sequence and timing are provided by a
separate heat control module. The RTRM only provides
the heating outputs to initiate 1
st
and 2
nd
stages and
control the combustion blower relay. Both stages of the
furnace will start and operate for one minute and then
cycle back if only one stage is required. Units with
modulating heat capabilities will light on high fire for one
minute and then modulate to the appropriate heating rate
for the building load present.
Electric Heat Control
The RTRM provides two heating outputs for 1st and 2nd
stages that will be controlled with at least a 10 seconds
delay between each stage. When the fan selection switch
is in the “AUTO” mode, the fan will start approximately 1
second before the 1st heater stage is activated. The fan
and heater will cycle off after the heating setpoint has been
satisfied. Once the Zone Heating requirements have been
satisfied, the fan and heat outputs will be controlled off.
Table 16. Economizer configuration
Selection
Dry Bulb
Enthalpy Value
A
73°F
27 BTU/LB Air
B
70°F
25 BTU/LB Air
C
67°F
23 BTU/LB Air
D
63°F
22 BTU/LB Air
E
55°F
19 BTU/LB Air