Related Points - United Technologies Carrier Weathermaker 48A2 Controls, Start-Up, Operation, Service, And Troubleshooting

higher supply 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 sup-
ply 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 de-
livering 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
(SPRESET which is part of the equipment controller). In the
algorithm 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
cannot be less than zero. The result is that the system will
dynamically determine the required duct static pressure based
on the actual load conditions currently in the space. This elimi-
nates the need to calculate the design supply static pressure set-
point. This also saves the energy difference between the design
static pressure setpoint and the required static pressure.
ITEM
SP SUPPLY STATIC PRESS.CFG.
SP.CF Static Pres. VFD Control?
CV.FD Constant VOL IDF is VFD
SP.FN Static Pres. Fan Control?
SP.S Static Pressure Sensor
SP.LO Static Press. Low Range
SP.HI Static Press. High Range
SP.SP Static Pressure Setpoint
SP.MN VFD Minimum Speed
SP.MX VFD Maximum Speed
SP.FS VFD Fire Speed Override
HT.V.M VFD Heating Minimum Speed
SP.RS Stat. Pres. Reset Config
SP.RT SP Reset Ratio (/dF)
SP.LM SP Reset Limit in iwc ()
SP.EC SP Reset Econo.Position
S.PID STAT.PRESS.PID CONFIGS
SP.TM Static Press. PID Run Rate
SP.P Static Press. Prop. Gain
SP.I Static Press. Intg. Gain
SP.D Static Press. Derv. Gain
SP.SG Static Press. System Gain
* Some defaults are model number dependent.
† 33-67 when CV.FD = Yes.
** 67 when CV.FD = Yes.
ITEM
Inputs
 4-20  SP.M
Static Pressure mA
 4-20  SP.M.T
Static Pressure mA Trim
 4-20 SP.R.M
Static Pressure Reset mA
 RSET SP.RS
Static Pressure Reset
Outputs
 Fans  S.VFD
Supply Fan VFD Speed
Table 60 — Static Pressure Control Configuration
EXPANSION
0, 1
Yes/No
Yes/No
Enable/Disable
–10 - 0
0 - 10
0 - 5
0 - 100†
0 - 100
0 - 100
75-100
0 - 4
0 - 2.00
0 - 2.00
0 - 100
1 - 200
0 - 100
0 - 50
0 - 50
0 - 50
Table 61 — Static Pressure Reset Related Points
EXPANSION
4-20
-2.0 - +2.0
4-20
0.0-3.0
0-100
Third Party 4 to 20 mA Input — It is also possible to perform
static pressure reset via an external 4 to 20 mA signal connect-
ed 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 sensors cannot be used at the
same time. To enable the static pressure reset 4 to 20 mA
sensor, set (Configuration
RELATED POINTS — These points represent static pressure
control and static pressure reset inputs and outputs. See Table 61.
Static Pressure mA (SP.M) — This variable reflects the value
of the static pressure sensor signal received by the ComfortLink
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 trans-
ducer 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 reset signal applied to TB6
terminals 11 and 12 on the CEM board, from a third party con-
trol system.
Static Pressure Reset (SP.RS) — This variable reflects the
value of a static pressure reset signal applied from a CCN sys-
tem. 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.
RANGE UNITS
in. W.C.
in. W.C.
in. W.C.
%
%
%
%
%
sec
RANGE UNITS
mA
mA
mA
in. wg
%
56
 
SP SP.RS) to Enabled.
CCN POINT DEFAULT
STATICFG
CVIDFVFD
STATPFAN
SPSENS Disable*
SP_LOW
SP_HIGH
SPSP
STATPMIN
STATPMAX
STATPFSO
VFDHTMIN
SPRSTCFG
SPRRATIO
SPRLIMIT
ECONOSPR
SPIDRATE
STATP_PG
STATP_IG
STATP_DG
STATP_SG
CCN POINT DEFAULT
SP_MA
SPMATRIM
SPRST_MA 0.0
SPRESET 0.0
SFAN_VFD
0*
No
Yes*
0
5
1.5
20**
100
100
75
0
0.2
0.75
5
2
20
2
0
1.0