Ecm Interface Board | 35; Dehumidification Method Selector - Bosch SM024 Installation, Operation And Maintenance Manual

SM Series Heat Pump
[8] Reheat digital outputs
[9] Thermostat outputs
[10] 24 VAC

[11] Dehumidification method selector

CFM LED indication is an approximation. Utilize
conventional Test and Balance equipment for
accurate airflow measurement.
• CFM count indicator (Figure #102 item [6])
blinks to indicate approximate airflow in CFM
and may flicker when the unit if off.
• 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.
Thermostat Outputs
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
H Dehumidification Mode
Airflow Selector
The airflow selector (Figure #102, items [2] & [3])
allows airflow adjustment to meet application
requirements and to ease troubleshooting.
Only one dip switch can be enabled at a time.
Refer to Figure #103 for each airflow setting.
• CFM Selector (Figure #102, Item [2]) must
remain with only "A" being enabled.
Revised 02-15

ECM INTERFACE BOARD | 35

• ADJUST Selector can be adjusted to NOM, (+),
(-), or TEST. NOM, (+) and (-) can be adjusted
as needed by application. TEST is used for
troubleshooting to override unit airflow to
100%.
Figure # 103
Do not set the ADJ DIP switch to the (-)
setting when electric heaters are installed.
Doing so may cause the heaters to cycle on
their thermal overload switches, potentially
shortening the life of the switches.
Always disconnect power before changing
DIP switch positions on the interface board
and reset the unit afterward.
Dehumidification Method Selector
Dehumidification method selector (Figure #102,
item [11]) is used to select between the following
two methods:
1. Units equipped with optional Hot Gas Reheat,
on dehumidification call (the "H" terminal on
the thermostat is energized) the reheat
outputs will energize the hot gas reheat valve
in the circuit and the heat pump will start in
dehumidification mode. Dehumidification
selector (Figure #102, item [11]) should be
selected to 'YES'.
2. Units without optional Hot Gas Reheat, on
dehumidification call, the heat pump fan will
operate at a lower speed to increase
dehumidification while cooling.
Dehumidification selector ((Figure #104, item
[11]) should be selected to 'NO'.
In this mode, the heat pump will only dehumidify
the space when it is running in cooling mode.
6 720 220 406 (2015/02)