Thermostat Connections - Bosch FHP EC Large Series Installation, Operation And Maintenance Manual

EC Series

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 Electronic
Commutated Motor (ECM) DC fan motor and
displays an LED indication of operating status. The
thermostat connections and their functions are as
follows:
Y1 First Stage Compressor Operation
Y2 Second 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 (not used in
EC Series)
If the unit is being connected to a thermostat with
a malfunction light, this connection is made at the
unit malfunction output or relay.
If the thermostat is provided with a malfunction
light powered off of the common (C) side of the
transformer, a jumper between "R" and "COM"
terminal of the "ALR" contacts must be made.
If the thermostat is provided with a malfunction
light powered off of the hot (R) side of the
transformer, then the thermostat malfunction
light should be connected directly to the (ALR)
contact on the unit's UPM board.
To the left of the thermostat connection block are
a row of 2 red and 4 green LED's. These LED's
indicate the operating status of the unit. They are
labeled as follows:
EC Series
EM (Red) Emergency Heat On
W1 (Red Auxiliary Heat On
O (Green) Reversing Valve Energized, unit is
in Cooling Mode
Y2 Second Stage Compressor On
(Green)
Y1 First Stage Compressor On
(Green)
G (Green) Fan On
Just above the connector block is a single red
LED labeled CFM that will blink intermittently
when the unit is running and may flicker when
the unit is off.
This LED indicates the air delivery of the blower at
any given time. Each blink of the LED represent
approximately 100 CFM of air delivery so if the LED
blinks 12 times, pauses, blinks 12 times, etc. the
blower is delivering approximately 1200 CFM. for
factory programmed air delivery settings for the EC
Series.
To the right of the thermostat connection block is
a green LED labeled dehumidify.
Just above and to the right of the thermostat
connection block are four sets of jumper pins
labeled ADJ, DELAY, HEAT and COOL. The ADJ set
of pins are labeled NORM, (+), (-) and TEST. EC
units will all be set on the NORM position from the
factory, however, airflow can be increased (+) or
decreased (-) by 15% from the pre-programmed
setting by relocating the jumper in this section.
The TEST position is used to verify proper motor
operation. If a motor problem is suspected, move
the ADJ jumper to the TEST position and energize
G on the thermostat connection block. If the motor
ramps up to 100% power, then the motor itself is
functioning normally. Always remember to rEClace
the jumper to NORM, (+) or (-) after testing and
reset the unit thermostat to restore normal
operation.
Thermostat Connections | 9
T111970289 (2015/01)