104
VAV BOARD (ECB2) — The VAV board (which is the same
hardware as the ECB1) is used to control the supply fan on
VAV units. See Fig. 30. It sends a 4 to 20 mA signal to the VFD
based on a supply duct pressure sensor connected to the board.
The board also accepts a signal from another pressure sensor
that monitors building pressure and controls the operation of
the optional modulating power exhaust motors. The board will
also be used on CV units with the optional building pressure
control feature and modulating power exhaust. This board is
also used to control a digitally controlled hot gas bypass sole-
noid with an integral orifice for use in low load applications.
This board is located in the auxiliary control box. Input and
output assignments are summarized in Table 103.
STAGED GAS HEAT BOARD (SCB) — When optional
staged gas heat is used on CV and VAV units, the SCB board is
installed and controls operation of the gas valves. See Fig. 31.
The SCB also provides additional sensors for monitoring of
the supply-air temperature. This board is located in the gas heat
section of the unit. The inputs and outputs are summarized in
Table 104.
ROOFTOP CONTROL BOARD (RXB) — The RXB is
used in place of ECB2 on all unit sizes with optional digital
scroll compressor and or optional Humidi-MiZer system. The
board has additional inputs to sense the digital compressor dis-
charge temperature. The board has additional outputs to control
digital scroll modulation. This board is located in the auxiliary
control box. Input and output assignments are summarized in
Table 105.
CONTROL EXPANSION MODULE (CEM) — The optional
CEM (also available as an accessory) is used to accept inputs
for additional sensors or control sequence switches, including:
• smoke control mode field switches
• VAV supply air temperature setpoint reset using an external
4 to 20 mA signal
• outdoor air CO
2
sensor (for supply duct pressure reset using
an eternal 4 to 20 mA signal)
• external fan status pressure switch input (CV units)
• demand limit sequence proportional signal or discrete
switches
The CEM board is located in the main control box. See
Fig. 32. The inputs and outputs are summarized in Table 106.
COMPRESSOR PROTECTION CURRENT SENSOR
BOARD (CSB) — This board monitors the status of the com-
pressor by sensing the current flow to the compressors and then
provides digital status signal to the MBB.
EXPANSION VALVE CONTROL BOARD (EXV) — The
EXV is used on Humidi-MiZer
®
equipped units only. It is used
to provide control of the condenser and bypass modulating
valves, as well as having additional inputs to sense the evapora-
tive discharge temperature. See Fig. 33 and Table 107.
INTEGRATED GAS CONTROL (IGC) — One IGC is pro-
vided with each bank of gas heat exchangers (2 used on the size
020-050 units and 3 on size 060 units). The IGC controls the
direct spark ignition system and monitors the rollout switch,
limit switches, and induced-draft motor Hall Effect switch. The
IGC is equipped with an LED (light-emitting diode) for diag-
nostics. See Table 108.
LOW AMBIENT SCREW COMPRESSOR BOARD
(SCB2) — The SCB2 is used on optional low ambient Motor-
master equipped units only. It is used to provide control of the
VFD to the condenser fans.
PHASE LOSS PROTECTION MONITOR OPTION
(PLP) — If all 3 phases of electrical supply are relatively equal
and in proper sequence, the normally open contacts (Y/Y-
OUT) will close when 24 volts is applied between C and Y ter-
minals. If the phases are out of sequence, or if one is missing,
the contacts will never close. If a phase is lost while the phase
monitor is energized, the contacts will open immediately and
will remain open until the error is corrected.
Summary of Contents for Carrier Weathermaker 48A2
Page 105: ...105 Fig 20 Typical Main Control Box Wiring Schematic 48 50A2 A3 A4 A5 Units...
Page 106: ...106 Fig 21 Typical Auxiliary Control Box Wiring Schematic...
Page 107: ...107 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown a48 8357...
Page 108: ...108 TO NEXT PAGE Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown A48 7296...
Page 109: ...109 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont A48 8358...
Page 110: ...110 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown a50 8228...
Page 111: ...111 Fig 25 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown...
Page 112: ...112 Fig 26 Typical Low Ambient Controls Option Wiring...
Page 113: ...113 Fig 27 Typical Small Chassis Component Location Size 020 035 Units...
Page 114: ...114 Fig 28 Typical Large Chassis Component Locations Size 040 060 Units...
Page 118: ...118 Fig 30 Economizer Control Board ECB1 and VAV Control Board ECB2 A48 7706...
Page 142: ...142 A48 3733 Fig 56 Main Burner Removal...
Page 176: ...176 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716...
