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eCM Interface board
Properly sized fuses or HACR circuit breakers must
be installed for branch circuit protection. See unit
nameplate for maximum fuse or breaker size.
The unit is provided with a concentric knock-out in
the front left corner post for attaching common
trade sizes of conduit, route power supply wiring
through this opening. Always connect the ground
lead to the grounding lug provided in the control box
and power leads to the power supply terminal block
as indicated on the wiring diagram and Figure #5.
Units supplied with internal electric heat
require two (2) separate power supplies: one
for the unit compressor and one for the electric
heater elements, blower motor and control
circuit. Refer to the ELECTRIC HEATER
PACKAGE OPTION section and Figure #8 for
wiring instructions, minimum circuit ampacities
and maximum fuse/breaker sizing.
figure #5 - electrical box Component layout
Revised 03-11
SINGLE & TWO STEP
Subject to change without prior notice
figure #6 eCM Interface board
eCM InTerfACe boArd
THerMoSTAT ConneCTIonS
Thermostat wiring is connected to the 10 pin screw type
terminal block on the lower center portion of the ECM
Interface Board. In addition to providing a connecting
point for thermostat wiring, the interface board also
translates thermostat inputs into control commands for
the variable speed programmable ECM DC fan motor and
displays an LED indication of operating status. The
thermostat connections and their functions are as
follows:
Y2
Second Stage Compressor Operation
Y1
First Stage Compressor Operation
G
Fan
O
Reversing Valve (energized in cooling)
W1
Auxiliary Electric Heat (runs in
conjunction with compressor)
EM/W2
Emergency Heat (electric heat only)
NC
Transformer 24 VAC Common (extra
connection)
C1
Transformer 24 VAC Common (primary
connection)
R
Transformer 24 VAC Hot
HUM
Dehumidification Mode
If the unit is being connected to a thermostat with a
malfunction light, this connection is made at the
unit malfunction output or relay.
6 720 220 046
7
TA Series
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