Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 159

Table 106 — TR1 Status LEDs
LED NAME POINT DESCRIPTION
ON
Power
SR Start relay during timer no. 1 duration
MR
Modulating relay - lit after timer no. 1 times out
FR Fan relay - lit when inducer fan runs on high speed
CR
Control relay - lit when gas valve is in high pressure stage.
Table 107 — SC30 Board Inputs and Outputs
TERMINAL TYPE OF I/O
INPUTS
1
24 Vac Input
from TR1
2
7
4-20 mA Input
from SCB
8
OUTPUTS
3
0-20 Vdc Output Output to Modulating Gas Valve
4
5, 6 Relay Output
NAVIGATOR™ DISPLAY
This device is the interface used to access the control informa-
tion, read sensor values, and test the unit. The Navigator dis-
play is a 4-line, 20-character, LCD display as well as an Alarm
Status LED. See Fig. 36. The display is easy to operate using 4
buttons and a group of 11 LEDs that indicate the following
menu structures:
• Run Status
• Service Test
• Temperatures
• Pressures
• Set points
• Inputs
• Outputs
• Configuration
• Timeclock
• Operating Modes
• Alarms
The RXB and EXB boards contain a second LEN port that can
be used with the handheld Navigator display.
Fig. 36 — Accessory Navigator Display
RESULT/ACTION
Powers SC30
Sets Output to Modulating Gas
Valve
Starts TR1 Timer no. 2
CONTROL MODULE COMMUNICATIONS
Red LED
Proper operation of the control boards can be visually checked
by looking at the red status LEDs as shown on Fig. 32-35.
When operating correctly, the red status LEDs should blink in
unison at a rate of once every 2 seconds. If the red LEDs are
not blinking in unison, verify that correct power is being sup-
plied to all modules. Also, be sure that the main base board is
supplied with the current software and that all boards are con-
figured on. If necessary, reload current software. If the problem
still persists, a board may need to be replaced. A board LED
that is lit continuously or blinking at a rate of once per second
or faster indicates that the board should be replaced.
Green LED
The boards also have a green LED, which is the indicator of the
operation of the LEN communications, which is used for com-
munications between the boards. On the MBB board the local
equipment network (LEN) LED should always be blinking
whenever power is on. All other boards have a LEN LED that
will blink whenever power is on and there is communication oc-
curring. If LEN LED is not blinking, check LEN connections for
potential communication errors (J3 and J4 connectors). A 3-wire
sensor bus accomplishes communication between modules.
These 3 wires run in parallel from module to module.
Yellow LED
The MBB has one yellow LED. The Carrier Comfort Network
(CCN) LED will blink during times of network communication.
The other boards do not have a CCN communications port.
CARRIER COMFORT NETWORK
The 48/50N Series units can be connected to the CCN if de-
sired. The communication bus wiring is a shielded, 3-
conductor cable with drain wire and is field supplied and in-
stalled. See the Installation Instructions for wiring information.
The system elements are connected to the communication bus
in a daisy chain arrangement. The positive pin of each system
element communication connector must be wired to the posi-
tive pins of the system elements on either side of it. This is also
required for the negative and signal ground pins of each system
element. Wiring connections for CCN should be made at the
COMM board. See Fig. 37. Consult the CCN Contractor's
Manual for further information.
NOTE: Conductors and drain wire must be 20 AWG (Amer-
ican Wire Gage) minimum stranded, tinned copper. Individ-
ual conductors must be insulated with PVC, PVC/nylon, vi-
nyl, Teflon , or polyethylene. An aluminum/polyester 100%
1
foil shield and an outer jacket of PVC, PVC/nylon, chrome
vinyl, or Teflon with a minimum operating temperature
range of –20°C to 60°C is required.
It is important when connecting to a CCN communication bus
that a color-coding scheme be used for the entire network to
simplify the installation. It is recommended that red be used for
the signal positive, black for the signal negative and white for
the signal ground. Use a similar scheme for cables containing
different colored wires.
At each system element, the shields of its communication bus
cables must be tied together. If the communication bus is entirely
within one building, the resulting continuous shield must be con-
nected to a ground at one point only. If the communication bus
cable exits from one building and enters another, the shields
must be connected to grounds at the lightning suppressor in each
building where the cable enters or exits the building (one point
per building only).
1. Teflon is a registered trademark of DuPont.
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