Ingersoll-Rand ReliaTel, Manual, Page: 143 / 176

RT-SVD03L-EN 143
remote min position setpoint will be used for the
design min position and the DCV min position.
Sequence of Operation
When the unit is in the occupied mode, the outdoor-air
(OA) damper opens to the DCV min position setpoint. If
the space CO
2
level is less than or equal to the lower
limit CO
2
setpoint, the OA damper will close to the DCV
min position setpoint. If the space CO
2
level is greater
than or equal to the upper level CO
2
setpoint, the OA
damper will open to the design min position Setpoint.
If the space CO
2
level is greater than the lower limit
CO
2
setpoint and less than the upper limit CO
2
setpoint, the OA damper position is modulated
proportionally between the DCV min and the design
min position setpoints. If there is a call for economizer
cooling, the outdoor air damper may be opened further
to satisfy the cooling request.
Figure 91. Damper position
Design Min OA
Damper Position
Setpoint
(10% - 50%)
DCV Min OA
Damper Position
Setpoint
(0% - 40%)
DCV Min CO
2
Setpoint
(300 ppm - 1,900 ppm)
Design Min CO
2
Setpoint
(1,000 ppm - 2,000 ppm)
Min OA Damper
Position Target
Space CO
2
Level
CO
2
Level
When the unit is in the unoccupied mode, DCV control
is deactivated.
N No otte e:: When using CO
2
-based DCV with an RTRM (v8.0
or later) and also an RTEM, set the design min
position setpoint to the minimum outdoor
airflow required by the local building code. The
DCV min position setpoint is typically based on
either 1) the minimum exhaust airflow rate from
the building or 2) the base ventilation rate
required to dilute building- or process-related
contaminants. See HVAC Knowledge Center
wave52581 for guidance on determining the CO
2
setpoints and OA damper position setpoints for a
given application.
During normal occupied mode, if the unit is not actually
heating or cooling, and the fan switch is set to auto, the
supply fan will be off. If the unit is configured for active
DCV control (DCV Mode OPEN), the supply fan will be
energized when the space CO
2
level rises above the
lower limit CO
2
setpoint and the DCV algorithm will be
in control of the outdoor air damper position. When the
space CO
2
level falls below the lower limit CO
2
setpoint
minus 50 ppm, DCV control will begin to close the
damper to the DCV min position setpoint. Once the
space CO
2
level is below the lower limit CO
2
setpoint
minus 50 ppm and the OA damper is at the DCV min
position the supply fan will de-energize if not requested
ON by another function.
The RTEM allows the selection of either active or
passive DCV control. Installing a jumper across J10-1
and J10-2 on the RTEM module configures the unit for
passive DCV control. When configured for passive DCV
control, DCV control is not allowed to force on the
supply fan, and DCV control will only be allowed when
the supply fan is on (commanded ON by another
function, such as comfort heating or cooling control, or
the supply fan mode set to ON). Passive DCV will
operate identically to active DCV once the supply fan is
energized.
IIm mp po orrtta an ntt:: While the ReliaTel ™ will allow active DCV
control when the fan mode is set to AUTO
(cycle on and off with the compressor or
heater), this practice is discouraged
because it can result in excessive fan
cycling and may not comply with ASHRAE
Standard 62.1. If CO
2
-based DCV is used,
the supply fan mode should be set to ON
(operate whenever the zone is occupied) or
the unit should be configured for passive
DCV control.
RTEM w/ RTRM v7.0 and Earlier
For units equipped with an RTRM v7.0 or earlier and
also an RTEM, the control will utilize a single CO
2
Setpoint and two separate Damper Minimum Position
Setpoints as described below:
Setpoint Selection
Units equipped with an RTRM v7.0 or earlier will utilize
a single CO
2
setpoint. The RTEM will use this setpoint
and space CO
2
input value to determine the active OA
damper position setpoint between the Bldg Design Min
Position and DCV min position setpoints.
For DCV control in these units, the CO
2
setpoint will
have a range of 500 to 1500 ppm. The Bldg Design Min
Position will be set using the onboard potentiometer
which will have a range of 10 to 50% and the DCV min
position will be set using the onboard potentiometer
which will have a range of 0 to 40%. This scheme
enforces a 10% differential between the Bldg Design
Min Position and the DCV min position setpoints.
Sequence of Operation
For units equipped with RTRM v7.0 or earlier and an
RTEM, only active DCV control is available, as the DCV
mode configuration input is not recognized prior to
RTRM v8.0.
Supply Fan Mode = ON
When the unit is in the occupied mode, the outdoor-air
(OA) damper opens to the DCV min position setpoint. If
the space CO
2
level rises above the CO
2
setpoint, the
OA damper will open to the Bldg Design Min Position
Setpoint. If the space CO
2
level drops below the CO
2
D De em ma an nd d C Co on nttrro oll V Ve en nttiilla attiio on n ((D DC CV V))