
39
as 0 ohms = 0% and 10,000 ohms = 100%, thereby giving com
-
plete range control of the effective minimum position.
NOTE: For complete economizer control, the user can make
the economizer inactive by unplugging the enthalpy switch
connection.
CONTROLS OPERATION
Modes
The
Comfort
Link controls operate under a hierarchy of com
-
mand structure as defined by 3 essential elements: the System
mode, the HVAC mode, and the Control mode. The System
mode is the top level mode that defines 3 essential states for the
control system: OFF, RUN, and TEST.
The HVAC mode is the functional level underneath the System
mode, which further defines the operation of the control.
The Control mode is essentially the control type of the unit
(
Configuration
UNIT
C.TYP
). This defines from where
the control looks to establish a cooling or heating mode.
Furthermore, there are a number of modes which operate con
-
currently when the unit is running. The operating modes of the
control are located at the local displays under
Operating
Modes
.
See Table 24.
Table 24 —
Operating Modes Display Table
MODES CONTROLLING UNIT
Currently Occupied (OCC)
This variable displays the
current occupancy state of the unit.
Timed Override in Effect (T.OVR)
This variable displays if the state of occupancy is currently oc
-
cupied due to an override.
DCV Resetting Minimum Position (DCV)
This variable displays if the economizer position has been low
-
ered from its maximum vent position due to demand controlled
ventilation.
Supply Air Reset (SA.R)
This variable displays if the supply air set point that the rooftop
is attempting to maintain is currently being reset upwards. This
applies to cooling only.
Demand Limit in Effect (DMD.L)
This variable displays if the mechanical cooling capacity is
currently being limited or reduced by a third party.
Temperature Compensated Start (T.C.ST)
This variable displays if Heating or Cooling has been initiated
before occupancy to pre-condition the space.
IAQ Pre-Occupancy Purge Active (IAQ.P)
This variable displays if the economizer is open and the fan is
on to pre-ventilate the building before occupancy.
Linkage Active CCN (LINK)
This variable displays if a linkage master in a zoning system
has established “linkage” with this air source (rooftop).
Mechanical Cooling Locked Out (LOCK)
This variable displays if mechanical cooling is currently being
locked out due to low outside air temperature.
HVAC Mode Numerical Form (H.NUM)
This is a numerical representation of the HVAC modes which
may be read via a point read.
SYSTEM MODES (
OPERATING MODES
SYS.M
)
System Mode Off
When the system mode is OFF, all outputs are to be shut down
and no machine control is possible. The following list displays
the text assigned to the System Mode when in the OFF mode
and the conditions that may cause this mode are checked in the
following hierarchal order:
1. Wake up timer on a power reset. (“Initializing System ...”)
2. System in the process of shutting down compressors and
waiting for timeguards to expire. (“Shutting Down ...”)
3. Factory shut down (internal factory control level —
SHUTDOWN). (“Factory Shut Down”)
4. Unit Stop (software application level variable that acts as a
hard shut down —
Service Test
STOP
). (“Local
Machine Stop”)
5. Fire Shut Down (fire shutdown condition based on the Fire
Shutdown Input (
Inputs
FIRE
FSD
). (“Fire-Shutdown
Mode”)
6. Emergency Stop, which is forced over the CCN through the
Emergency Stop Variable (EMSTOP). (“CCN Emergency
Stop”)
7. Start-up Delay. (“Startup Delay = 0-900 secs”)
8. Service test ending transition timer. (“Service Test Ending”)
9. Unexplained internal software failure. (“Internal Failure”)
System Mode Test
When the system mode is Test, the control is limited to the Test
mode and is controllable via the local displays (Navigator™
display). The System Test modes are Factory Test Enabled and
Service Test Enabled. See the Service Test section on page 29
for details on test control in this mode.
1. Factory Test mode (“Factory test enabled”)
2. Service Test mode (“Service test enabled”)
System Mode Run
When the system mode is Run, the software application in the
control is free to run the HVAC control routines by which cool
-
ing, heating, IAQ, etc., is possible. There are 2 possible text
displays for this mode; one is normal run mode and the other
occurs if one of the following fire-smoke modes is present:
smoke purge, pressurization, or evacuation.
1. Normal run time state (“Unit Operation Enabled”)
2. Fire-Smoke control mode (“Fire-Smoke Control”)
HVAC MODES
(
OPERATING MODE
HVAC
)
The HVAC mode is dependent on the system mode to allow it
to further determine the operational state of the rooftop unit.
The actual determination of an HVAC mode is based on a hier
-
archal decision-making process whereby certain overrides may
interfere with normal temperature/humidity control. The deci
-
sion-making process that determines the HVAC mode is shown
in Fig. 3 and Appendix E.
Each HVAC mode is described below. The HVAC mode num
-
ber is shown in the parentheses after the mode.
HVAC Mode — STARTING UP (0)
The unit is transitioning from the OFF mode to a different mode.
ITEM
EXPANSION
RANGE CCN POINT
SYS.M
ascii string
n/a
HVAC
ascii string
n/a
CTRL
ascii string
n/a
MODE
MODES CONTROLLING UNIT
OCC
Currently Occupied
Off/On MODEOCCP
T.OVR
Timed Override in Effect
Off/On MODETOVR
DCV
DCV Resetting Min Pos
Off/On MODEADCV
SA.R
Supply Air Reset
Off/On MODESARS
DMD.L
Demand Limit in Effect
Off/On MODEDMLT
T.C.ST
Temp.Compensated Start
Off/On MODETCST
IAQ.P
IAQ Pre-Occ Purge Active
Off/On MODEIQPG
LINK
Linkage Active — CCN
Off/On MODELINK
LOCK
Mech.Cooling Locked Out
Off/On MODELOCK
H.NUM
HVAC Mode Numerical Form number MODEHVAC
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 ...