Carrier /50HC 04-28, Controls, Start-Up, Operation And Troubleshooting, Page: 77 / 144

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Main Base Board (MBB)
See Fig. 32 and Table 29. The MBB is the center of the Com-
fort Link control system. It contains the major portion of the
operating software and controls the operation of the unit. The
MBB continuously monitors input/output channel information
received from its inputs and from the Economizer Control
Board (ECB). The MBB receives inputs from thermistors and
transducers. The MBB also receives the Current Sensor inputs
for compressors and other discrete or digital inputs. The MBB
reads space temperature (SPT) from either a T-55, T-56 or T-58
device and space temperature offset (SPTO) from a T-56 de-
vice. See Field-Installed Accessories section. The MBB con-
trols 11 relays.
NOTE: The Main Base Board (MBB) has a 3-position instance
jumper that is factory set to ‘1.’ Do not change this setting.
Fig. 32 — Main Base Board (MBB)
CEPL1 3 0 3 46-01
S TATU S
LEN
J1 J2
J4
J 3
J5
J6
J7
J 8 J9
J10
CCN
RED LED - S TATU S GREEN LED -
LEN (LOCAL EQUIPMENT NETWORK) YELLOW LED -
CCN (CARRIER COMFORT NETWORK)
IN S TANCE JUMPER ( S ET TO 1)
C07026