RT-SVF69C-EN
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Sequence of Operation
3. To set the Design and DCV Minimum Position setpoints
at Full Fan Speed, set the unit to operate at Step 4 (Cool
2) and make the proper adjustments.
Economizer Damper Position Set-Up
without DCV
For units not configured with DCV (no CO
2
sensor value
available), additional minimum position setpoints to
increase outdoor airflow accuracy will be supported. The
operation will be similar to OA CFM Compensation on
Traditional VAV units with the addition of a Design
Minimum Position setpoint at Middle Fan Speed
Command. The following setpoint potentiometers will be
used on the RTEM:
1.
Design Min at Minimum Fan Speed Command (RTEM
DCV Min)
2. Design Min at Middle Fan Speed Command (RTEM
DCV Setpoint LL)
3. Design Min at Full Fan Speed Command (RTEM Design
Min)
The controller will calculate the active OA Damper
Minimum position between the user-selected setpoints
based on the supply fan speed command. By Default, the
Design Minimum Position schedule will be a linear line
through all user selectable Design Minimum Position
setpoints. As with Demand Controlled Ventilation, if the
Design Minimum Position at Middle fan speed command
is set to a point that would be higher than the calculated
linear line between the Design Minimum Position
setpoints at Minimum and Maximum fan speed
command, the minimum position will be limited to the
point that would make the Design Minimum Position
schedule linear.
Provisions have been made in Service Test Mode to allow
for proper damper minimum position setup:
1.
To set the Design Minimum Position setpoint at
Minimum Fan Speed, set the unit to operate at Step 1
(Fan ON) or Step 2 (Economizer Open) and make the
proper adjustment.
2. To set the Design Minimum Position setpoint at Middle
Fan Speed, set the unit to operate at Step 3 (Cool 1) and
make the proper adjustment.
3. To set the Design Minimum Position setpoint at Full
Fan Speed, set the unit to operate at Step 4 (Cool 2) and
make the proper adjustment.
Heating Operation
Heating operation on units configured with Single 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. For Modulating Gas
heat units, the unit will have the ability to control the
discharge air temperature to the calculated discharge air
heating setpoint in order to maintain the Zone
Temperature to the Zone Heating setpoint.
Staged Heating Operation
For units configured with Staged Heat once the control
determines that there is an active heating capacity
request, the unit will energize the Supply Fan and ramp up
to full speed. The control methodology during Active
Heating on units configured with Staged Heat types will be
identical to traditional Constant Volume units; heating
stages will be energized/de-energized to meet the Zone
Heating demand.
Note:
All Electric and Gas Heat staging sequences will be
identical to Constant Volume unit staging
sequences.
Modulating Heat Operation with SZVAV
Heating
Units configured with Modulating Gas Heat will utilize true
Single Zone VAV control in the same manner as during
Active Cooling.
Heating Sequence
Once the unit control determines that there is a space
heating demand, the unit will transition into zone heating.
Once the Discharge Air Temperature falls below the
calculated discharge air temperature setpoint, the unit will
initiate the Modulating Heat output request and control
the supply fan at minimum speed. At this point, the
Modulating Heat output will be controlled to maintain the
discharge air temperature requirements and the supply
fan speed will be controlled between 63%-100% to meet
the zone heating requirements.
As the heating load in the zone decreases the fan speed
will decrease down to minimum (63%) and control the
modulating heat output as necessary to meet the
discharge air heating requirements. As the load in the zone
continues to drop the fan speed will be maintained at this
minimum airflow and the modulating heat output will be
controlled accordingly.
Low Ambient Operation
The indoor fan motor (IDM) will operate at 100% fan speed
during this evaporator defrost cycle (EDC) and the
compressor and outdoor fan will return to normal
operation once the defrost cycle has terminated and the
compressor "Off" time delay has been satisfied.
Clogged Filter Option
The unit mounted clogged filter switch monitors the
pressure differential across the return air filters. It is
mounted in the indoor section and is connected to the
RTOM. The clogged filter switch is normally open and will
automatically close when the pressure differential across
the filters falls below the clogged filter setpoint. The RTOM
will generate a SERVICE diagnostic that will be sent to the