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81
In addition, it should be noted that the economizer cooling al
-
gorithm is designed to automatically slow down the economiz
-
er actuator’s rate of travel as outside-air temperature decreases.
See Table 55.
ECONOMIZER DIAGNOSTIC HELP
Because there are so many conditions which might disable the
economizer from being able to provide free cooling, the con
-
trol offers a handy place to identify these potentially disabling
sources. All the user has to do is check
ACTV
, the “Economiz
-
er Active” flag. If this flag is set to “Yes” there is no reason to
explore the group under
DISA
, the “Economizer Disabling
Conditions.” If the flag is set to “No,” this means that at least
one or more of the flags under the group
DISA
are set to “Yes”
and the user can easily discover exactly what is preventing the
economizer from performing “free cooling.”
In addition, the economizer’s reported and commanded posi
-
tions are viewable, as well as one convenient place to view out
-
side-air temperature, relative humidity, enthalpy, and dew point
temperature.
The following information can be found under the local display
mode
Run Status
ECON.
Economizer Control Point Determination Logic
Once the economizer is allowed to provide free cooling, the
economizer must determine exactly what set point it should try
to maintain. The set point the economizer attempts to maintain
when “free cooling” is located at
Run Status
VIEW
EC.C.P
.
This is the economizer control point.
The control selects set points differently, based on the control
type of the unit. This control type can be found at
Configura
-
tion
UNIT
C.TYP
.
There are 4 types of control.
C.TYP
= 1
VAV-RAT
C.TYP
= 2
VAV-SPT
C.TYP
= 3
TSTAT Multi-Staging
C.TYP
= 4
SPT Multi-Staging
If the economizer is not allowed to do free cooling, then
EC.C.P
= 0.
If the economizer is allowed to do free cooling and the Unoc
-
cupied Free Cooling Mode is ON, then
EC.C.P
= Set
-
points
SASP
+
Inputs
RSET
SA.S.R
.
If the economizer is allowed to do free cooling and the Dehu
-
midification mode is ON, then
EC.C.P
= the Cooling Control
Point (
Run Status
VIEW
CL.C.P
).
NOTE: To check the current cooling stage, go to
Run Status
Cool
CUR.S
.
If the
C.TYP
is either 1, 2, 3, or 4, and the unit is in a cool
mode, then
EC.C.P
= the Cooling Control Point (
Run Status
VIEW
CL.C.P
).
Single Act CFM Ctl Activ (SACA)
Indication whether single actuator CFM control is active.
NO = Single actuator cfm control is not currently active. The
unit will use both outside air actuators for cfm control.
YES = Single actuator cfm control is currently active. The unit
will use a single outside air actuator for cfm control, and the
other outside air actuator shall be commanded closed.
The status indicator shall be forcible to allow the operator to
force single actuator cfm control. The status shall be automati
-
cally cleared (set to NO) if:
1 = Fire/smoke emergence is active
2 =
E.SAC
=NO
Table 55 —
Economizer Run Status Table
ITEM
EXPANSION
RANGE
UNITS
CCN POINT
WRITE STATUS
EC1.P
Economizer 1 Out Act. Curr. Pos.
0-100
%
ECONOPOS
EC2.P
Economizer 2 Ret. Act.Curr.Pos.
0-100
%
ECON2POS
EC3.P
Economizer 3 Out Act.Curr.Pos.
0-100
%
ECON3POS
ECN.C
Economizer Out Act.Cmd.Pos.
0-100
%
ECONOCMD
forcible
ACTV
Economizer Active ?
No/Yes
ECACTIVE
SACA
Single Act CFM Ctl Activ
No/Yes
SACFMCTL
forcible
DISA
ECON DISABLING CONDITIONS
UNV.1
Econ Out Act. Unavailable?
No/Yes
ECONUNAV
UNV.2
Econ2 Ret Act. Unavailable?
No/Yes
ECN2UNAV
UNV.3
Econ3 Out Act. Unavailable?
No/Yes
ECN3UNAV
ENTH
Enth. Switch Read High ?
No/Yes
ENTH
DBC
DBC - OAT Lockout?
No/Yes
DBC_STAT
DEW
DEW - OA Dewpt.Lockout?
No/Yes
DEW_STAT
DDBC
DDBD- OAT > RAT Lockout?
No/Yes
DDBCSTAT
OAEC
OAEC- OA Enth Lockout?
No/Yes
OAECSTAT
DEC
DEC - Diff.Enth.Lockout?
No/Yes
DEC_STAT
EDT
EDT Sensor Bad?
No/Yes
EDT_STAT
OAT
OAT Sensor Bad ?
No/Yes
OAT_STAT
FORC
Economizer Forced?
No/Yes
ECONFORC
SFON
Supply Fan Not On 30s?
No/Yes
SFONSTAT
CLOF
Cool Mode Not In Effect?
No/Yes
COOL_OFF
OAQL
OAQ Lockout in Effect?
No/Yes
OAQLOCKD
HELD
Econ Recovery Hold Off?
No/Yes
ECONHELD
DH.DS
Dehumid. Disabled Econ.?
No/Yes
DHDISABL
O.AIR
OUTSIDE AIR INFORMATION
OAT
Outside Air Temperature
dF
OAT
forcible
OA.RH
Outside Air Rel. Humidity
%
OARH
forcible
OA.E
Outside Air Enthalpy
OAE
OA.D.T
Outside Air Dewpoint Temp
dF
OADEWTMP
Summary of Contents for WeatherExpert 48N2
Page 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Page 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Page 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Page 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Page 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Page 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Page 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Page 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Page 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Page 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Page 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Page 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Page 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...