Electrical; Electric Heater Package Option; Low Voltage Control Wiring - Bosch SM024 Installation, Operation And Maintenance Manual

8 | Electrical

If the unit will be installed in a new installation
which includes new duct work, the installation
should be designed using current ASHRAE
procedures for duct sizing. If the unit is to be
connected to existing ductwork, a check should be
made to assure that the duct system has the
capacity to handle the air required for the unit
application. If the duct system is too small, larger
ductwork should be installed. Check for existing
leaks and repair as necessary to ensure an air tight
seal within the duct.
The duct system and all diffusers should be sized
to handle the designed air flow quietly. To
maximize sound attenuation of the unit blower, the
supply and return air plenums should be insulated.
There should be no direct straight air path thru the
return air grille into the heat pump. The return air
inlet to the heat pump must have at least one 90
degree turn away from the space return air grille. If
air noise or excessive air flow are a problem, the
blower speed can be changed to a lower speed to
reduce air flow. (Refer to ECM motor interface
board section in this manual and Figure #8)
ELECTRICAL
Always disconnect power to the unit before
servicing to prevent injury or death due to
electrical shock or contact with moving
parts.
All field wiring must comply with local and national
fire, safety and electrical codes. Power to the unit
must be within the operating voltage range
indicated on the unit's nameplate.
Operating the unit with improper line
voltage or with excessive phase imbalance
is hazardous to the unit and constitutes
abuse and is not covered under warranty.
Properly sized fuses or HACR circuit breakers must
be installed for branch circuit protection. See
equipment rating plates for maximum size.
Both the air handler and condensing units are
provided with a concentric knock-out in the front
right corner post for attaching common trade sizes
of conduit. Route power supply wiring through this
opening. Flexible wiring and conduit should be
used to isolate vibration and noise from the
building structure. Be certain to connect the
ground lead to the ground lug in each of the
control boxes. Connect the power leads as
indicated on the unit wiring diagrams.
8733920846 (2015/01)

Electric Heater Package Option

Factory installed internal electric heater packages
are available for all unit sizes, in certain
configurations; not available in straight-through
configuration for supply air in horizontal models.
Two circuit breakers are required when heater
packages are utilized. The circuit breakers for the
heater package provide power for the heater
elements, the blower motor and the control circuit
for the unit. The circuit breaker for the unit
provides power for the compressor. This allows
the electric heaters to continue to operate along
with the blower motor in the case of unit
compressor and/or compressor power supply
failure. See HK Series Heater Kit Instructions for
field installation. Each SM Series model has a
number of heater sizes available. Refer to Figure #9
for heater package compatibility with specific SM
Series units, models nomenclature and electrical
data.

Low Voltage Control Wiring

The SM series units incorporate the ECM variable
speed fan motor and control interface board. The
thermostat should be connected to the air
handlers and then from the air handler to the
condensing section. The low voltage power supply
is located in the air handler.
In this application utilize a 9 conductor cable from
the thermostat to the air handler and 7 conductor
cable from the air handler to the condensing
section.
Each model has a number of heater sizes available.
Refer to Figure#12 for heater package compatibili-
ty with specific units, model nomenclature and
electrical data
Subject to change without prior notice
SM AH Series Heat Pump
SM AH Series Heat Pump