59
Therefore, the amount to add to the economizer’s ECONOMIN
configuration is: (0.5/0.75) x (50-20) = 20%. In effect, for the
positioning of the economizer, ECONOMIN would now be re-
placed by EC 10%.
Static Pressure PID Config (S.PID)
Static pressure PID configuration can be accessed under this
heading in the
Configuration
SP
submenu. Under most op-
erating conditions the control PID factors will not require any
adjustment and the factory defaults should be used. If per-
sistent static pressure fluctuations are detected, small changes
to these factors may improve performance. Decreasing the fac-
tors generally reduces the responsiveness of the control loop,
while increasing the factors increases its responsiveness. Note
the existing settings before making changes, and seek technical
assistance from Carrier before making significant changes to
these factors.
Static Pressure PID Run Rate (
S.PID
SP.TM
) —
This is the
number of seconds between duct static pressure readings taken
by the
Comfort
Link PID routine.
Static Pressure Proportional Gain (
S.PID
SP.P
) —
This is
the proportional gain for the static pressure control PID control
loop.
Static Pressure Integral Gain (
S.PID
SP.I
) —
This is the in-
tegral gain for the static pressure control PID control loop.
Static Pressure Derivative Gain (
S.PID
SP.D
) —
This is the
derivative gain for the static pressure control PID control loop.
Static Pressure System Gain
(
S.PID
SP.SG
) — This is the
system gain for the static pressure control PID control loop.
STATIC PRESSURE RESET OPERATION
The
Comfort
Link controls support the use of static pressure re-
set. The Linkage Master terminal monitors the primary air
damper position of all the terminals in the system (done
through LINKAGE with the new ComfortID™ air terminals).
The Linkage Master then calculates the amount of supply static
pressure reduction necessary to cause the most open damper in
the system to open more than the minimum value (60%) but
not more than the maximum value (90% or negligible static
pressure drop). This is a dynamic calculation, which occurs ev-
ery two minutes whenever the system is operating. The calcu-
lation ensures that the supply static pressure is always enough
to supply the required airflow at the worst case terminal but
never more than necessary, so that the primary air dampers do
not have to operate with an excessive pressure drop (more than
required to maintain the airflow setpoint of each individual ter-
minal in the system).
As the system operates, if the most open damper opens more
than 90%, the system recalculates the pressure reduction vari-
able and the value is reduced. Because the reset value is subtract-
ed from the controlling setpoint at the equipment, the pressure
setpoint increases and the primary-air dampers close a little (to
less than 90%). If the most open damper closes to less than 60%,
the system recalculates the pressure reduction variable and the
value is increased. This results in a decrease in the controlling
setpoint at the equipment, which causes the primary-air dampers
to open a little more (to greater than 60%).
The rooftop unit has the static pressure setpoint programmed
into the CCN control. This is the maximum setpoint that could
ever be achieved under any condition. To simplify the installa-
tion and commissioning process for the field, this system con-
trol is designed so that the installer only needs to enter a maxi-
mum duct design pressure or maximum equipment pressure,
whichever is less. There is no longer a need to calculate the
worst case pressure drop at design conditions and then hope
that some intermediate condition does not require a higher sup-
ply static pressure to meet the load conditions. For example, a
system design requirement may be 1.2 in. wg, the equipment
may be capable of providing 3.0 in. wg and the supply duct is
designed for 5.0 in. wg. In this case, the installer could enter
3.0 in. wg as the supply static pressure setpoint and allow the
air terminal system to dynamically adjust the supply duct static
pressure setpoint as required.
The system will determine the actual setpoint required deliver-
ing the required airflow at every terminal under the current
load conditions. The setpoint will always be the lowest value
under the given conditions. As the conditions and airflow set-
points at each terminal change throughout the operating period,
the equipment static pressure setpoint will also change.
The CCN system must have access to a CCN variable (SPRE-
SET which is part of the equipment controller). In the algo-
rithm for static pressure control, the SPRESET value is always
subtracted from the configured static pressure setpoint by the
equipment controller. The SPRESET variable is always
checked to be a positive value or zero only (negative values are
limited to zero). The result of the subtraction of the SPRESET
variable from the configured setpoint is limited so that it can-
not be less than zero. The result is that the system will dynami-
cally determine the required duct static pressure based on the
actual load conditions currently in the space. This eliminates
the need to calculate the design supply static pressure setpoint.
This also saves the energy difference between the design static
pressure setpoint and the required static pressure.
Third Party 4 to 20 mA Input
It is also possible to perform static pressure reset via an exter-
nal 4 to 20 mA signal connected to the CEM board where 4
mA corresponds to 0 in. wg of reset and 20 mA corresponds to
3 in. wg of reset. The static pressure 4 to 20 mA input shares
the same input as the analog OAQ sensor. Therefore, both sen-
sors cannot be used at the same time. To enable the static pres-
sure reset 4 to 20 mA sensor, set (
Configuration
SP
SP.RS
) to Enabled.
RELATED POINTS
These points represent static pressure control and static pres-
sure reset inputs and outputs. See Table 60.
Static Pressure mA (SP.M)
This variable reflects the value of the static pressure sensor sig-
nal received by the
Comfort
Link controls. The value may be
helpful in troubleshooting.
Static Pressure mA Trim (SP.M.T)
This input allows a modest amount of trim to the 4 to 20 mA
static pressure transducer signal, and can be used to calibrate a
transducer.
Static Pressure Reset mA (SP.R.M)
This input reflects the value of a 4 to 20 mA static pressure re-
set signal applied to TB6 terminals 11 and 12 on the CEM
board, from a third party control system.
Static Pressure Reset (SP.RS)
This variable reflects the value of a static pressure reset signal
applied from a CCN system. The means of applying this reset
is by forcing the value of the variable SPRESET through CCN.
Supply Fan VFD Speed (S.VFD)
This output can be used to check on the actual speed of the
VFD. This may be helpful in some cases for troubleshooting.
Summary of Contents for WEATHERMAKER 48A2020
Page 112: ...112 Fig 20 Typical Main Control Box Wiring Schematic 48 50A Units ...
Page 113: ...113 Fig 21 Typical Auxiliary Control Box Wiring Schematic ...
Page 114: ...114 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown ...
Page 115: ...115 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown TO NEXT PAGE ...
Page 116: ...116 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont ...
Page 117: ...117 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown ...
Page 118: ...118 Fig 25 Typical Controls Option Wiring Schematic SW1 SW2 OR DEHUMIDIFY SWITCH ...
Page 119: ...119 Fig 26 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown ...
Page 120: ...120 Fig 27 Typical Power Schematic of Greenspeed Low Ambient Option 48 50A 060 Unit Shown ...
Page 121: ...121 Fig 28 Typical Small Chassis Component Location Size 020 035 Units ...
Page 122: ...122 Fig 29 Typical Large Chassis Component Locations Size 040 060 Units ...
Page 185: ...185 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716 ...