Sequence of Operation
46 RT-SVX25Q-EN
Economizer Damper Position Set-Up with
DCV
This new scheme will require the setting of 5 OA Damper
position setpoints; 3 more than on non-SZ VAV. These new
setpoints are located on the RTVM module:
1. Design Min Position @ Minimum Fan Speed
Com
mand (RTVM
R130)
2. Design Min Position @ Middle Fan Speed Command
(RTVM R136)
3. Design Min Position @ Full Fan Speed Command
(RTE
M Design Min Position)
4. DCV Min Position @ Minimum Fan Speed Command
(RTVM R41)
5. DCV Min position @ Full Fan Spee
d Command (RTEM
DCV Min Position)
As the supply fan speed command varies between
minimu
m and maximum, the Building Design and DCV
Minimum Position Targets will be calculated between the
user selected setpoints based on the instantaneous supply
fan speed. The Bldg. Design and DCV Minimum Position
Targets will be used to calculate the Active OA Damper
Minimum Position Target, as on traditional units, based on
the Space CO
2
relative to the active Design and DCV CO
2
setpoints.
By default, the Design Minimum Position schedule will be
a li
near li
ne through all user selectable Design Minimum
Position setpoints. The user will have the ability to set the
Design Minimum Position at Middle fan speed command
to a point that would be lower than the calculated linear
line between the Design Minimum Position setpoints at
0% and 100% fan speed command in order to compensate
for the non-linear outside airflow through the fan and
damper modulation range. However, 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 Full 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
fo
r prop
er damper minimum position setup:
1. To set the Design and DCV M
in
imum Position setpoints
at Minimum Fan Speed, set the unit to operate at Step
1 (Fan ON) or Step 2 (Economizer Open) and make the
proper adjustments.
2. To set the Design Minimum Position setpoint at Middle
Fan Speed, set the
unit to ope
rate at Step 3 (Cool 1) and
make the proper adjustment.
3. To set the Design and DCV Min
imum 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
Comman
d (RTEM
DCV Setpoint LL)
3. Design Min at Full Fan Speed Command (RTEM Design
Mi
n)
The con
troller will calculate the active OA Da
mper
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
fo
r prop
er 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
Fa
n
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
Fa
n
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 the unit will utilize 100% full
airflow during all active heating periods like traditional
Constant Volume units.
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
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