Electronic Thermostat Installation - Bosch SM Series Installation, Operation And Maintenance Manual

SM Split AH/AV Air Handler
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.
Fig. 11 Electrical Component Box Layout
[1] ECM Board
[2] Transformer
[3] Unit Terminal Block
[4] Unit Ground Lug

Electronic Thermostat Installation

The unit heat pump can be controlled by most
commonly available single-stage heat pump
thermostats. Note that the reversing valve (located
in the SM Split Condensing Section) is energized
when the unit is in the cooling mode. Thermostats
should be located on an interior wall away from
supply ducts. Avoid locations subject to direct
sunlight, drafts, external walls. Thermostat wiring
should be 18 AWG (American Wire Gauge) for up
to 60 foot, 16 AWG up to 100 ft, and 14 AWG up to
140 ft. Refer to the installation instructions of the
thermostats for further details.
When using a 2-cool, 3-heat thermostat
both the W1 & W2 on the Heat Pump and
W2 & EM on the thermostat must be
connected together via a jumper. See
Fig. 12.
SM Split AH/AV Air Handler
Fig. 12 Thermostat Jumpers
The SM Air Handlers are equipped with
detachable Thermostat connectors located
on the ECM Interface board. Refer to unit
wiring diagram for connection details.
Depending on the options installed, some
wires in the Wiring Harness may not be
utilized. See Wiring Harness Drawing notes
for further details.
Subject to change without prior notice
Electrical | 11
8733826256 (2020/06)