85
OPERATION
The unit’s indoor air quality algorithm modulates the position
of the economizer dampers between 2 user configurations de
-
pending upon the relationship between the
IAQ
and the out
-
door air quality (
OAQ
). Both of these values can be read at the
Inputs
AIR.Q
submenu. The lower of these 2 configurable
positions is referred to as the IAQ Demand Vent Min Position
(
IAQ.M
), while the higher is referred to as Economizer Mini
-
mum Position (
EC.MN
). The
IAQ.M
should be set to an econ
-
omizer position that brings in enough fresh air to remove con
-
taminants and CO
2
generated by sources other than people.
The
EC.MN
value should be set to an economizer position that
brings in enough fresh air to remove contaminants and CO
2
generated by all sources including people. The
EC.MN
value is
the design value for maximum occupancy.
The logic that is used to control the dampers in response to
IAQ conditions is shown in Fig. 12. The
Comfort
Link controls
will begin to open the damper from the
IAQ.M
position when
the IAQ level begins to exceed the OAQ level by a configu
-
rable amount, which is referred to as Differential Air Quality
Low Limit (
DAQ.L
).
If OAQ is not being measured, OAQ can be manually config
-
ured. It should be set at around 400 to 450 ppm or measured
with a handheld sensor during the commissioning of the unit.
The OAQ reference level can be set using the OAQ Reference
Set Point (
OAQ.U
). When the differential between IAQ and
OAQ reaches the configurable Diff. Air Quality Hi Limit
(
DAQ.H
), then the economizer position will be
EC.MN
.
When the IAQ–OAQ differential is between
DAQ.L
and
DAQ.H
, the control will modulate the damper between
IAQ.M
and
EC.MN
as shown in Fig. 12. The relationship is a linear re
-
lationship but other non-linear options can be used. The damp
-
er position will never exceed the bounds specified by
IAQ.M
and
EC.MN
during IAQ control.
Fig. 12 —
IAQ Control
If the building is occupied and the indoor fan is running and the
differential between IAQ and OAQ is less than
DAQ.L
, the
economizer will remain at
IAQ.M
. The economizer will not
close completely. The damper position will be 0 when the fan
is not running or the building is unoccupied. The damper posi
-
tion may exceed
EC.MN
in order to provide free cooling.
The
Comfort
Link controls are configured for air quality sen
-
sors which provide 4 mA at 0 ppm and 20 mA at 2000 ppm. If
a sensor has a different range, these bounds must be reconfig
-
ured. These pertinent configurations for ranging the air quality
sensors are
IQ.R.L, IQ.R.H, OQ.R.L
and
OQ.R.H
. The bounds
represent the PPM corresponding to 4 mA (low) and 20 mA
(high) for IAQ and OAQ, respectively.
If OAQ exceeds the OAQ Lockout Value (
OAQ.L
), then the
economizer will remain at
IAQ.M
. This is used to limit the use
of outside air which outdoor air CO
2
levels are above the
OAQ.L
limit. Normally a linear control of the damper vs. the
IAQ control signal can be used, but the control also supports
non-linear control. Different curves can be used based on the
Diff.IAQ Responsiveness Variable (
IAQ.R
)
. See Fig. 13.
SETTING UP THE SYSTEM
The IAQ configuration options are under the Local Display
Mode
Configuration
IAQ
. See Table 57.
Fig. 13 —
IAQ Response Curve
IAQ Analog Sensor Config (Configuration
IAQ
AQ.CF
IQ.A.C)
This is used to configure the type of IAQ position control. It
has the following options:
•
IQ.A.C
= 0 (No analog input). If there is no other mini
-
mum position control, the economizer minimum position
will be
Configuration
IAQ
DCV.C
EC.MN
and there
will be no IAQ control.
•
IQ.A.C
= 1 (IAQ analog input). An indoor air (space or re
-
turn air) CO
2
sensor is installed. If an outdoor air CO
2
sen
-
sor is also installed, or OAQ is broadcast on the CCN, or if
a default OAQ value is used, then the unit can perform
IAQ control.
•
IQ.A.C
= 2 (IAQ analog input with minimum position
override) — If the differential between IAQ and OAQ is
above
Configuration
IAQ
AQ.SP
DAQ.H
, the econ
-
omizer minimum position will be the IAQ override posi
-
tion (
Configuration
IAQ
AQ.SP
IQ.O.P
).
100
500
700
1000
INSIDE/OUTSIDE CO
2
DIFFERENTIAL
INSIDE CO
2
CONCENTRATION
AQ
DIFFERENTIAL
LOW (DAQ.L)
AQ
DIFFERENTIAL
HIGH (DAQ.H)
MINIMUM
IAQ
DAMPER
POSITION
ECONOMIZER
MINIMUM
DAMPER
POSITION
INCREASING VENTILA
TION
VENTILATION FOR PEOPLE
VENTILATION FOR SOURCES
NOTE: Calculating the IAQ.M and EC.MN damper position based
on differential IAQ measurement.
Based on configuration parameter IAQREACT, the reaction to damper
positioning based on differential air quality ppm can be adjusted.
IAQREACT = 1 to 5 (more responsive)
IAQREACT = 0 (linear)
IAQREACT = –1 to –5 (less responsive)
Содержание WeatherExpert 48N2
Страница 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Страница 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Страница 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Страница 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Страница 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Страница 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Страница 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Страница 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Страница 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Страница 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Страница 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Страница 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Страница 168: ...168 Fig 47 Sensor and Ignition Position Fig 48 Combustion Blower Details SENSOR DETAILS IGNITION DETAILS ...
Страница 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...