Bryant Legacy 547K 14, Installation Instructions Manual

Page: 17 / 44

17
Fig. 31 — Typical Low-Voltage Control Connections
Unit without Thru-Base Connection Kit
Pass the thermostat control wires through the bushing on the
unit end panel. Route the wire through the snap-in wire tie and
up to the web bushing near the control box. Route the wire
through the bushing and into the bottom left side of the control
box after removing one of the 2 knockouts in the corner of the
box. Use a connector at the control box to protect the wire as it
passes into the control box. Pull the wires over to the terminal
strip at the upper left corner of the Unit Control Board (UCB).
Use the connector at the control box and the wire tie to take up
any slack in the thermostat wire to ensure that it will not be
damaged by contact with the condenser coil. See Fig. 32.
NOTE: If thru-the-bottom connections accessory is used, refer to
the accessory installation instructions for information on routing
power and control wiring.
Heat Anticipator Settings
Set heat anticipator settings at 0.14 amp for the first stage and
0.14 amp for second-stage heating, when available.
Fig. 32 — Thermostat Wire Routing
COMMERCIAL DEFROST CONTROL
On 547K units equipped with electromechanical controls the
Defrost Control Board (DFB) coordinates thermostat demands
for supply fan control, 2 stage cooling, 2 stage heating,
emergency heating and defrost control with unit operating se -
quences. The DFB also provides an indoor fan off delay feature
(user selectable). See Fig. 33 for board arrangement.
The DFB is located in the main control box of the 547K unit
(see Fig. 34). All connections are factory-made through har -
nesses to the UCB (unit control board) to the ECM (direct-
drive motor), reversing valve solenoids and to defrost
thermostats. Refer to Table 3 for details of DFB Inputs and
Outputs.
Fig. 33 — Defrost Control Board Arrangement
Reversing Valve Control
The DFB has 2 outputs for unit reversing valve control. Opera -
tion of the reversing valves is based on internal logic; this
application does not use an “O” or “B” signal to determine re -
versing valve position. Reversing valves are energized during
the cooling stages and the defrost cycle and de-energized
during heating cycles. Once energized at the start of a cooling
stage, the reversing valve will remain energized until the next
heating cycle demand is received. Once de-energized at the
start of a Heating cycle, the reversing valves will remain de-
energized until the next cooling stage is initiated.
Compressor Control
The DFB receives inputs indicating Stage 1 Cooling, Stage 2
Cooling and Stage 1 Heating from the space thermostat or unit
control board (UCB); it generates commands to start compressors
with or without reversing valve operation to produce Stage 1 Cool -
ing (one compressor runs), Stage 2 Cooling (both compressors
run) or Stage 1 Heating (both compressors run).
Auxiliary (Electric) Heat Control
The 547K unit can be equipped with one or 2 auxiliary electric
heaters, to provide a second stage of heating. The DFB will en -
ergize this Heating System for a Stage 2 Heating Command
(heaters operate concurrently with compressor(s) in the Stage 1
Heating cycle), for an Emergency Heating sequence
(compressors are off and only the electric heaters are ener -
gized) and also during the Defrost cycle (to eliminate a “cold
blow” condition in the space).
C
HUM
G
W2
R
C
W2
G
W1
O/B/Y2
Y2
W1
R
Y1 Y1
T
H
E
R
M
O
S
T
A
T
(Note 1) (Note 2)
(Note 3)
1. Typical multi-function marking. Follow manufacturer’s configuration
instructions to select Y2.
2. Y2 to Y2 connection required on single-stage cooling units when
integrated economizer function is desired.
3. W2 connection not required on units with single-stage heating.
Field Wiring
Unit Control
Board
NOTES:
Typical
Thermostat
Connections
Thermostat Wire
DIP
Switches
Speed-Up
Jumpers