Bosch SM SERIES User manual

Installation, Operation, and Maintenance Manual
SM Split AH/AV Air Handler
8733826256 (2020/06)
SM024 | SM036 | SM048 | SM060

SM Split AH/AV Air Handler
SM Split AH/AV Air Handler8733826256 (2020/06)
2 |
Subject to change without prior notice
Document Conventions .......................................................3
Key to Symbols............................................................ 3
Safety Warnings..................................................................3
Model Nomenclature ...........................................................4
CS/Air Handler Pairings.......................................................5
SM Split AH/AV Standard Package .......................................6
General Description ..................................................... 6
Moving and Storage ..................................................... 6
Initial Inspection.......................................................... 6
Unit Installation ..................................................................7
Location Selection...............................................................7
Air Handler Location..................................................... 7
Condensing Section Location ........................................ 7
Installation .........................................................................7
Air Handler Section Installation...................................... 8
Hanging Bracket Kit...................................................... 8
Condensate Drain........................................................ 9
Duct System .....................................................................10
Electrical ..........................................................................10
Electronic Thermostat Installation ................................ 11
Low-Voltage Connection Points ................................... 12
ECM Interface Board .................................................. 13
Thermostat Connections............................................. 13
Refrigerant Lines ..............................................................15
Linear vs. Equivalent Line Length ................................. 15
Connecting Refrigerant Lines....................................... 16
Typical System Setup ........................................................18
Specific Application Considerations ...................................19
Well Water Systems ................................................... 19
Cooling Tower/Boiler Systems..................................... 19
Geothermal Systems.................................................. 19
Post-Installation System Checkout .....................................20
System Operation .............................................................20
Unit Start-up.....................................................................20
Sequence of Operation ......................................................20
Options ............................................................................22
Electric Heat ............................................................. 22
Troubleshooting................................................................23
Unit Lockouts............................................................ 25
Maintenance.....................................................................26
Decommissioning Information ...........................................27
Protecting the Environment......................................... 27
Check-Out Sheet ...............................................................28
Wiring Diagrams ............................................................... 29
Dimensional Drawings.......................................................31
Terminology ..................................................................... 33
Acronyms .................................................................33
Terms.......................................................................33
Notes ............................................................................... 34

Document Conventions | 3SM Split AH/AV Air Handler
8733826256 (2020/06)SM Split AH/AV Air Handler Subject to change without prior notice
DOCUMENT CONVENTIONS
Key to Symbols
Warnings
The following keywords are defined and can be
used in this document:
•DANGER indicates a situation that, if not avoided,
will result in death or serious injury.
•WARNING indicates a situation that, if not avoided,
could result in death or serious injury.
•CAUTION indicates a situation that, if not avoided,
could result in minor to moderate injury.
•NOTICE is used to address practices not related to
personal injury.
Important Information
SAFETY WARNINGS
Warnings in this document are identified by
a warning triangle printed against a gray
background. Keywords at the start of the
warning indicate the type and seriousness
of the ensuing risk if measures to prevent
the risk are not taken.
This symbol indicates important
information where there is no risk to
property or people.
IMPORTANT: Read the entire instruction
manual before starting installation.
WARNING: PERSONAL INJURY HAZARD
Installation and servicing of this equipment
can be hazardous due to system pressure
and electrical components. Only trained
and qualified personnel should install,
repair, or service the equipment.
WARNING: ELECTRIC SHOCK
Before performing service or maintenance
operations on the system, turn off main
power to the unit. Electrical shock could
cause personal injury or death.
WARNING: FLAMMABLE REFRIGERANT
R410A is flammable when exposed to open
flame. Recover all refrigerant prior to
brazing.
WARNING: When working on equipment,
always observe precautions described in
the literature, tags, and labels attached to
the unit. Follow all safety codes. Wear
safety glasses and work gloves. Use a
quenching cloth for brazing, and place a fire
extinguisher close to the work area.
NOTICE: To avoid the release of refrigerant
into the atmosphere, the refrigerant circuit
of this unit must be serviced only by
technicians who meet local, state, and
federal proficiency requirements.
NOTICE: All refrigerant discharged from this
unit must be recovered WITHOUT
EXCEPTION. Technicians must follow
industry accepted guidelines and all local,
state, and federal statutes for the recovery
and disposal of refrigerants. If a compressor
is removed from this unit, refrigerant circuit
oil will remain in the compressor. To avoid
leakage of compressor oil, refrigerant lines
of the compressor must be sealed after it is
removed.
NOTICE: To avoid equipment damage, DO
NOT use these units as a source of heating
or cooling during the construction process.
Doing so may affect the unit's warranty. The
mechanical components and filters will
quickly become clogged with construction
dirt and debris, which may cause system
damage or failure.
WARNING: This product can expose you to
chemicals including Lead and Lead
components, which are known to the State
of California to cause cancer and birth
defects or other reproductive harm.
For more information go to
www.P65Warnings.ca.gov.

SM Split AH/AV Air Handler
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4 | Model Nomenclature
Subject to change without prior notice
MODEL NOMENCLATURE
Fig. 1 Model Nomenclature
1 2 345
6
7 8910111213141516171819202122232425262728293031323334353637383940
SM 024
-
1AVX - XL TAT A- XHT XX XXXX 7XXXX4XXXXSBA
SERIES SM SIZE
024, 036, 048, 060
VOLTAGE
1 - 208–230/60/1
CABINET CONFIGURATION
AH - AIR HANDLER HORIZONTAL AV - AIR HANDLER VERTICAL
COAX WATER COIL X - N/A
WATER CONNECTIONS
X - N/A
RETURN AIR CONFIGURATION
L - LEFT R - RIGHT
DISCHARGE AIR CONFIGURATION
T - TOP (AV ONLY) S - STRAIGHT (AH ONLY) E - END (AH ONLY)
FAN/MOTOR OPTIONS A - CONSTANT AIRFLOW ECM
AIR COIL T - TIN-PLATED
REVISION LEVEL
CODE STRING LEVEL
STANDARD/SPECIAL
S - STANDARD
OPEN
DRIVE SPEED X - N/A
ELECTRIC HEAT
X -NONE A - 5 kW C - 10 kW D - 15 kW
CABINET CONSTRUCTION
H - PAINTED STEEL / 1/2" CLOSED-CELL FOAM
APPLICATION
T - TXV
GENERAL ELECTRICAL OPTIONS (UP TO 5 AVAILABLE PER UNIT)
REFRIGERATION CIRCUIT OPTIONS
X - NONE
MOTOR HP/QTY
X - N/A
AIR FILTRATION 4 - MERV 8 - 2” W/4-SIDED FILTER RACK
WATER FLOW CONTROL
X - N/A
CONTROLS
X - STANDARD
TRANSFORMER 7 - 75 VA
A - (SIZE 024, 048, 060) B - (SIZE 036)
X - AS DEFAULT FOR NON-USED ELECTRICAL CODES
CHANNEL
B - BOSCH
AGENCY OPTIONS
X - ETL (UL 1995)
OPEN OPEN

CS/Air Handler Pairings | 5SM Split AH/AV Air Handler
8733826256 (2020/06)SM Split AH/AV Air Handler Subject to change without prior notice
CS/AIR HANDLER PAIRINGS
UNIT MODEL Paired Air Handler
Paring 1 Pairing 2
SM024-1CS SM024-1AVX SM024-1AHX
SM036-1CS SM036-1AVX SM036-1AHX
SM048-1CS SM048-1AVX SM048-1AHX
SM060-1CS SM060-1AVX SM060-1AHX
LEGEND:
AVX BOSCH Box Style Vertical Air Handler
AHX BOSCH Box Style Horizontal Air Handler

SM Split AH/AV Air Handler
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6 | SM Split AH/AV Standard Package
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SM SPLIT AH/AV STANDARD PACKAGE
Fig. 2 SM Split Series Water-to-Air Heat Pump Air Handler
[1] SM Split Series Water-to-Air Heat Pump Air
Handler
[2] Installation and Operation Manual
General Description
SM Split Series Water-to-Air Heat Pumps provide
the best combination of performance and
efficiency available. All units are performance
certified to American Heating and Refrigeration
Institute (AHRI) ISO Standard 13256-1. All SM
Water-to-Air Heat Pumps conform to UL 1995
standard and are certified to CAN/CSA C22.1 No
236 by Intertek-ETL.
Split system heat pumps consist of two
independently installed sections allowing for
centralized air distribution while remotely locating
the section containing the compressor and
water-to-refrigerant heat exchanger (Coax Water
Coil).
In the cooling mode, the air coil in the air handler
section serves as an evaporator and the water-to-
refrigerant heat exchanger serves as a condenser.
In the heating mode, their roles are reversed.
In cooling mode, the refrigerant lines connecting
the two sections consist of one line carrying liquid
refrigerant and another carrying refrigerant vapor.
The liquid carrying line will be referred to as the
liquid line while the vapor carrying line will be
referred to as the suction line.
The Water-to-Air Heat Pumps are designed to
operate with entering fluid temperature between
20°F to 80°F in the heating mode and between
50°F to 110°F in the cooling mode.
Moving and Storage
If the equipment is not needed for immediate
installation upon its arrival at the job site, it should
be left in its shipping carton and stored in a clean
and dry area. Units must only be stored or moved
in the normal upright position as indicated by the
“UP” arrows on each carton at all times.
Initial Inspection
Be certain to inspect all cartons or crates on each
unit as received at the job site before signing the
freight bill. Verify that all items have been received
and that there are no visible damages; note any
shortages or damages on all copies of the freight
bill. In the event of damage or shortage, remember
that the purchaser is responsible for filing the
necessary claims with the carrier. Concealed
damages not discovered until after removing the
units from the packaging must be reported to the
carrier within 24 hours of receipt.
1
2
Antifreeze solution is required for entering
fluid temperatures below 50°F. Reference
the installation and operational manual for
the SM Condensing Section for additional
details based on unit application.
NOTICE: This product should not be used
for temporarily heating/cooling during
construction. Doing so may effect the units
warranty.

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UNIT INSTALLATION
This section contains information on the following:
LOCATION SELECTION
To maximize system performance, efficiency and
reliability, and to minimize installation costs, it is
always best to keep the refrigerant lines as short
as possible. Every effort should be made to locate
the air handler and the condensing section as
close as possible to each other.
Fig. 3 Air Handler and the Condensing Section
Air Handler Location
Locate the air handler unit in an indoor area that
allows easy removal of the filter and access panels,
and has enough room for service personnel to
perform maintenance or repair. Provide sufficient
room to make electrical and duct connections. If
the unit is located in a confined space such as a
closet, provisions must be made for return air to
freely enter that space.
Condensing Section Location
Locate the condensing section in an area that
provides sufficient room to make water and
electrical connections, and allows easy removal of
the access panels, for service personnel to
perform maintenance or repair. The condensing
section is designed for indoor use only.
INSTALLATION
Subject Page
Location Selection 7
Installation 7
Duct System 10
Electrical 10
Refrigerant Lines 15
Typical System
Setup
18
Specific Application
Considerations
19
Post-Installation
System Checkout
20
NOTICE: To avoid equipment damage, DO
NOT use these units as a source of heating
or cooling during the construction process.
Doing so may affect the unit’s warranty. The
mechanical components and filters will
quickly become clogged with construction
dirt and debris, which may cause system
damage.
NOTICE: These units are not approved for
outdoor installation; therefore, they must
be installed inside a structure in a
conditioned space. Do not locate in areas
that are subject to freezing.
Reference the installation and operation
manual for your SM Split Condensing
Section for detailed installation
instructions.
Remove all shipping blocks from the inside
and/or outside of the air handler section
prior to final installation.
WARNING: The installer should comply with
all local codes and regulations which govern
the installation of this type of equipment.
Local codes and regulations take precedent
over any recommendations contained in
these instructions. In lieu of local codes, the
equipment should be installed in
accordance with the recommendations
made by the National Electric Code, and in
accordance with the recommendations
made by the National Board of Fire
Underwriters.

SM Split AH/AV Air Handler
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8 | Installation
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Air Handler Section Installation
The air handler section may be installed on any
level surface strong enough to support its weight.
When installed in a closet or on a base stand, it
should be mounted on a vibration absorbing pad
slightly larger than the base to minimize vibration
transmission to the building structure.
Fig. 4 Vibration Pad
When installed in an attic or above a drop ceiling,
the installation must conform to all local codes.
Use the Hanging Bracket Kit to install the unit in a
horizontal position (supply air at the end or side of
the unit). The unit must be supported on all four
corners with threaded rods attached to the
building’s ceiling rafters.
Some applications require an attic floor
installation of the air handling unit. In this case the
unit should be set in a full-size secondary drain pan
on top of a vibration absorbing mesh. The
secondary drain pan prevents possible condensate
overflow or water leakage damage to the ceiling.
The secondary drain pan is usually placed on a
plywood base isolated from the ceiling joists by
additional layers of vibration absorbing mesh. In
both cases, a 3/4" drain connected to this
secondary pan should be run to an eave at a
location that will be noticeable. See Fig. 9.
If the air handler is located in a crawl space, the
bottom of the unit must be at least 4" above grade
to prevent flooding of the electrical parts due to
heavy rains.
Hanging Bracket Kit
All horizontal air handler units come with a
Hanging Bracket Kit to facilitate suspended unit
mounting using threaded rods.
Included Parts
Table 1 Hanging Bracket Kit Included Parts
Required Parts Not Included
The following are needed and are to be field
provided.
Table 2 Hanging Bracket Kit Field-Provided Parts
Installation Instructions
1. Remove and discard factory-provided screws
from the locations where hanging brackets will
be installed. See Fig. 5.
Fig. 5 Screw Locations
Vibration Pad
is
recommended
WARNING: Follow all applicable codes and
requirements when hanging this unit,
selecting threaded rod material, etc.
Quantity Description
5Brackets
5Rubber Vibration Isolators
8Screws #10 x 1/2”
Quantity Description
4Threaded Rods (3/8” maximum
diameter)
4Hex Nuts
4Washers (1–3/4” minimum O.D.)
Note: Additional fasteners specific to your
installation will be needed to attach the
threaded rods to the building’s rafters.

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2. Mount the four Brackets to unit’s four corner
posts using the screws provided in the kit.
Refer to Fig. 6 and Fig. 7.
Fig. 6 Four Bracket Mounting Locations
Fig. 7 Mounting Brackets to the Corner Posts
3. Install the Rubber Vibration Isolator grommets
onto the Brackets as shown in Fig. 8.
4. Hang the unit and assemble the field-provided
threaded rod, nuts, and washers on to the
brackets as shown in Fig. 8.
Fig. 8 Connecting the Threaded Rod to the Brackets
Condensate Drain
The air handler should be pitched approximately
1/4” towards the drain in both directions, to
facilitate condensate removal. A drain line must be
connected to the air handler and pitched away
from the unit a minimum of 1/8” per foot to allow
the condensate to flow away from the unit. This
connection must be in conformance with local
plumbing codes.
A trap must be installed in the condensate line to
ensure free flow of the condensate. A vertical air
vent is sometimes required to avoid air pockets.
See Fig. 9. The length of the trap depends on the
amount of positive or negative pressure on the
drain pan.
Fig. 9 Condensate Drain
WARNING: Do not re-use screws removed
from the unit on step 1 to mount the
Hanging brackets to the unit.
WARNING: Rods must be securely
anchored to the ceiling.
Plumbing connected to the heat pump must
not come in direct contact with joists,
trusses, walls, etc.
Never use a second trap.
Units are not internally trapped.

SM Split AH/AV Air Handler
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10 | Duct System
Subject to change without prior notice
The air handler should be pitched approximately
1/4" towards the drain in both directions, to
facilitate condensate removal. See Fig. 10.
Fig. 10 Air Handler Pitch
DUCT SYSTEM
A supply air outlet collar and return air duct flange
are provided on all units to facilitate duct
connections.
A flexible connector is recommended for supply
and return air duct connections on metal duct
systems. All metal ducting should be insulated
with a minimum of one inch duct insulation to
avoid heat loss or gain and prevent condensate
forming during the cooling operation. Application
of the unit to uninsulated duct work is not
recommended as the unit’s performance will be
adversely affected.
The factory provided air filter must be removed
when using a filter back return air grill. The factory
filter should be left in place on a free return
system.
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 duct work, a check should
be made to ensure that the duct system has the
capacity to handle the air required for the unit
application. If the duct system is too small, larger
duct work should be installed. Also, check for
existing leaks and repair.
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 through
the return air grill 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
Fig. 13.)
ELECTRICAL
Drain Pan is not internally sloped.
NOTICE: Do not connect discharge ducts
directly to the blower outlet.
WARNING: UNIT OPERATION AND SAFETY
HAZARD
Field wiring must comply with local and
National Electric Code (NEC).
WARNING: UNIT OPERATION AND SAFETY
HAZARD
Power to the unit must be within the
operating voltage range indicated on the
unit’s nameplate or on the performance
data sheet.
WARNING: UNIT OPERATION AND SAFETY
HAZARD
Properly-sized fuses or HACR circuit
breakers must be installed for branch
circuit protection. See the unit nameplate
for maximum fuse or breaker size.
NOTICE: Operation of unit on improper line
voltage or with excessive phase imbalance
will be hazardous to the unit, constitutes
abuse and may void the warranty.

Electrical | 11SM Split AH/AV Air Handler
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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.
Fig. 12 Thermostat Jumpers
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.
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.

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Low-Voltage Connection Points
Table 3 Low-Voltage Connection Points
Tables Notes:
1) If the condensate overflow sensor option is
utilized connect “CS” at the condensing section
to “CS” at the air handler. Be sure to ground
power supply.
2) If service LED is utilized connect “ALR” terminal
on the UPM board to “L” on the thermostat sub
base. The wiring may be spliced in the air
handling unit. The “ALR” output is hot (R) so
check thermostat instruction manual to ensure
compatibility.
3) “O” – reversing valve is energized in the cooling
mode. Fail safe is to heating.
4) Utilized when electric strip heater package
present.
5) Will vary depending on the thermostat.
Function From
Thermostat
To Air Handler From Air
Handler
To
Condensing
Section
24 VAC Common C C C C
24 VAC Power R R R R
Fan Operation G G — —
Reversing Valve3O O O O
Compressor 1st Stage Y1 Y1 Y1 Y1
Compressor 2nd Stage Y2 Y2 Y2 Y2
Condensate Sensor1— — CS CS
Alarm Output (from
UPM)2
L/ALR Splice ALR (UPM)
Auxiliary Electric Heat4W/W1/W2 W1 — —
Second-Stage Auxiliary
Heat/Emergency Heat4
W/E, W1/E, W2/E5W2 — —

Electrical | 13SM Split AH/AV Air Handler
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ECM Interface Board
In addition to providing a connection point for
thermostat wiring, the interface board also
translates thermostat inputs into control
commands for the Electronic Commutated Motor
(ECM) fan motor and provides thermostat signals
to the unit’s UPM board (located in the SM
condensing section).
Fig. 13 ECM Interface Board
[1] Motor Harness Plug
[2] Blower CFM Adjustment
[3] Motor Settings
[4] Dehumidification Indication
[5] Thermostat Contact Inputs
[6] CFM Count Indicator
[7] Thermostat Input Status Indication
[8] Reheat Digital Outputs
[9] Thermostat Outputs
[10] 24 VAC
[11] Dehumidification Method Selector
Thermostat Connections
Thermostat wiring is connected to the 10-pin
screw type terminal block on the lower-center
portion of the ECM Interface Board. (See Fig. 13)
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:
Table 4 Thermostat Connections
If the unit is being connected to a thermostat with
a malfunction light, this connection is made at the
unit alarm output.
On the above series units the thermostat wiring
connections are made at the air handling section.
This will allow the capability to utilize both the
condensate overflow switch and the alarm output.
Connection Function
Y2 Second-Stage Compressor
Operation
Y1 First-Stage Compressor Operation
GFan
OReversing Valve (energized in
cooling)
W1
Auxiliary Electric Heat
(runs as supplemental heat when
needed along with compressor)
W2 Second-Stage Auxiliary Heat/
Emergency Heat
CTransformer 24 VAC Common
(extra connection)
C1 Transformer 24 VAC Common
(primary connection)
RTransformer 24 VAC Hot
HUM Passive Dehumidification Mode
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
“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 connection
should be connected directly to the (ALR)
contact on the unit’s UPM board.

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Subject to change without prior notice
Bosch recommends the use of 18 AWG thermostat
conductive cable for up to 60 foot, 16 AWG up to
100 ft, and 14 AWG up to 140 ft. to wire from the
condensing section terminal strip to the air
handler terminal strip.
Connection point logic is as follows:
To the left of the thermostat connection block are
a row of 2 red and 4 green LEDs. These LEDs
indicate the operating status of the unit. (See Fig.
13.) They are labeled as follows:
Table 5 Connection Point Logic
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
100 CFM of air delivery so if the LED blinks 12
times, pauses, blinks 12 times, etc. the blower is
delivering 1200 CFM. Refer to Table 6 for
factory-programmed air delivery settings for the
SM Series.
Motor Profile Air-Flow Table CFM
Table 6 Motor Profile Air-Flow Table CFM
Just above and to the right of the thermostat
connection block are DIP Switches labeled ADJ,
DELAY, HEAT and COOL. The ADJ set of pins are
labeled NORM, (+), (-) and TEST. SM 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 replace
the jumper to NORM, (+) or (-) after testing and
reset the unit thermostat to restore normal
operation. (See Fig. 13.)
The other three sets of jumper pins are used to
Connection Color Operating Status
EM RED Emergency Heat ON
W1 RED Auxiliary Heat ON
OGREEN
Reversing Valve
Energized, unit is in
cooling mode
Y2 GREEN Second-Stage
Compressor ON
Y1 GREEN First-Stage
Compressor ON
GGREEN Fan ON
To the right of the thermostat connection
block is a green LED labeled dehumidify. On
dehumidification call the fan will operate at
a lower speed to increase dehumidification
while cooling.
Motor Fan
Only
Y1
Cool/Heat
Y2
Cool/Heat
AUX
Heat
Emerg.
Heat
Plus
ADJ
Minus
ADJ
Tap Cool/
Heat/Delay
SM024 450 500 800 800 800 900 700 A
SM036 700 1050 1225 1225 1225 1400 1050 A
SM048 900 925 1500 1500 1500 1700 1275 B
SM060 1200 1500 2000 2000 2000 2300 1700 A
NOTICE: Do not set the ADJ jumper 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.

Refrigerant Lines | 15SM Split AH/AV Air Handler
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select the proper program in the ECM motor for
the unit. Refer to Fig. 13 for the proper jumper
placement.
To the left of the red and green status LEDs is a
row of 1/4” male quick connects. (See Fig. 13.)
These are used to pass thermostat inputs on to the
rest of the control circuit. Remember to always
turn off unit power at the circuit breaker before
attaching or disconnecting any wiring from these
connections to avoid accidental short circuits that
can damage unit control components.
REFRIGERANT LINES
The installation of the copper refrigerant tubing
must be done with care to obtain reliable,
trouble-free operation. This installation should
only be performed by qualified refrigeration
service and installation personnel.
Refrigerant lines generally can and should be
routed and supported so as to prevent the
transmission of vibrations into the building
structure. Experience and good design practice
dictate 75 feet as the maximum practical length for
interconnecting refrigerant lines in split system
heat pumps without special considerations.
Beyond 75 feet, system losses become substantial
and the total refrigerant charge required can
compromise the reliability and design life of the
equipment.
Copper tubing should be clean and free of
moisture and dirt or debris. The suction and liquid
lines MUST be insulated with at least 3/8” wall,
closed-cell foam rubber insulation or the
equivalent.
Some points to consider are:
• Pressure drop (friction losses) in refrigerant
suction lines reduces system capacity and
increases power consumption by as much as
2% or more, depending on the line length,
number of bends, etc. Pressure drop in liquid
lines affects system performance to a lesser
degree, provided that a solid column of liquid
(no flash gas) is being delivered to the
refrigerant metering device, and that the liquid
pressure at the refrigerant metering device is
sufficient to produce the required refrigerant
flow.
• Oil is continually being circulated with the
refrigerant so, oil return to the compressor is
always a consideration in line sizing. Suction
lines on split system heat pumps are also hot
gas lines in the heating mode, but are treated
as suction lines for sizing purposes. If the
recommended suction lines sizes are used,
there should be no problem with oil return.
• Vertical lines should be kept to a minimum.
Vertical liquid lines will have a vertical liquid lift
in either heating or cooling, and the weight of
the liquid head is added to the friction loss to
arrive at the total line pressure drop.
• Wherever possible, the air handler should be
installed at a higher elevation than the
condensing section to aid with oil return to the
compressor.
Linear vs. Equivalent Line Length
Linear Line Length — is the actual measured length
of the line including bends. This is used to
calculate the additional refrigerant charge that
must be added to the system (See Table 8 and
Table 9 for charge information).
Equivalent Line Length — is the combination of the
actual length of all the straight runs and the
equivalent length of all bends valves and fittings in
a particular line. The equivalent length of a bend,
valve or fitting is equal to the length of a straight
tube of the same diameter having the same
pressure drop as the particular valve or fitting. The
ASHRAE Fundamentals Handbook provides tables
for determining the equivalent length of various
bends, valves and fittings.
NOTICE: Always disconnect power before
changing jumper positions on the interface
board and reset the unit afterward.

SM Split AH/AV Air Handler
SM Split AH/AV Air Handler8733826256 (2020/06)
16 | Refrigerant Lines
Subject to change without prior notice
Connecting Refrigerant Lines
• Use only ACR grade copper tubing and keep
ends sealed until joints are made.
• For best performance, select routing of
refrigerant lines for minimum distance and
fewest number of bends.
• Size lines in accordance with Table 8.
• Cut crimped ends off the air handler suction
and liquid lines. Connect and braze lines to the
air handler.
• Connect and braze lines to service valves on
the condensing section.
Valve Sizing Chart
Table 7 Valve Sizing Chart
Pressurize the refrigerant line set and air handler
to 150lbs with dry nitrogen through the ports
provided on the self service valves. Check line set
and unit connections for leaks.
Once system integrity is verified, evacuate line set
and air handler with a good vacuum pump to 500
microns and hold for half hour.
The air handler is factory supplied with a
holding charge of dry nitrogen.
NOTICE: Always wrap the body of the
service valve with a wet towel or apply some
other form of heat sink prior to brazing and
direct flame away from the valve body.
Failure to do so will result in damage to the
valve. Valve body temperature must remain
below 250°F to protect the internal rubber
“O” rings and seals.
Unit Size Line
Type
Valve
Conn.
Size
Hex
(Allen)
Wrench
Size
SM024/036 Suction 3/4 5/16
SM048/060 Suction 7/8 5/16
ALL Liquid 3/8 3/16
Pump down must never be used with heat
pumps.

Refrigerant Lines | 17SM Split AH/AV Air Handler
8733826256 (2020/06)SM Split AH/AV Air Handler Subject to change without prior notice
Refrigerant Charge, Line Sizing, and Capacity Multiplier Chart
Table 8 Refrigerant Charge, Line Sizing, and Capacity Multiplier Chart
Liquid Line Charge per Linear Foot
Table 9 Liquid Line Charge per Linear Foot
System
Models
Factory
R410A
Charge
(Oz)*
Refrigerant Line O.D. Size (Based on Equivalent Line Length) Suction
Line
Riser
Max.
25 FT. 36 FT. 45 FT. 50 FT. 75 FT.
LIQ. SUC. LIQ. SUC. LIQ. SUC. LIQ. SUC. LIQ. SUC.
SM024 80 3/8 3/4 3/8 3/4 3/8 3/4 3/8 3/4 3/8 7/8 3/4
SM036 86 3/8 3/4 3/8 3/4 3/8 3/4 3/8 7/8 3/8 7/8 3/4
SM048 88 3/8 7/8 3/8 7/8 3/8 7/8 3/8 7/8 3/8 7/8 7/8
SM060 115 3/8 1–1/8 3/8 1–1/8 3/8 1–1/8 3/8 1–1/8 3/8 1–1/8 7/8
CAPACITY MULTIPLIER 1.00 0.995 0.990 0.990 0.980
EXAMPLE 1:
Model SM036 with 45 ft. of equivalent length of 3/8” O.D.
Liquid Line.
Total System Charge= Factory Charge + (45 ft. - 25 ft.) x .60
oz./ft.
Total System Charge = 93 oz. + (20 ft. x .60 oz./ft.) = 105 oz.
Additional 12 oz. of R410A refrigerant required.
EXAMPLE 2:
Model SM060 with 10 ft. of equivalent length of 3/8” O.D.
Liquid Line.
Total system charge= Factory charge + (25 ft. -10 ft.) x .60 oz./ft.
Total System Charge = 150 oz. + (15 ft. x .60 oz./ft.) = 141 oz.
Additional 12 oz. of R410A refrigerant required.
LIQUID LINE
SIZE, O.D. 1/4 5/16 3/8 1/2 5/8
R410A OZ
PER FOOT .25 .44 .60 1.15 1.95

SM Split AH/AV Air Handler
SM Split AH/AV Air Handler8733826256 (2020/06)
18 | Typical System Setup
Subject to change without prior notice
TYPICAL SYSTEM SETUP
Fig. 14 Typical Setup
[1] Flex Duct Connection
[2] Low Voltage Control Connection
[3] Vibration Pad
[4] Ball Valves
[5] Solenoid Valve Slow Closing
[6] Condensate Drain Connection
[7] Drain Valves
[8] Hose Kits (optional)
[9] Pressure Tank (optional)
[10] P/T Ports (optional)
[11] Line Voltage Connection
[12] Electric Heater Line Voltage Disconnect
[13] Unit Line Voltage Disconnect
[14] Ground Loop Pumping Package
For Reference Only.
A typical setup is shown for
illustration purposes only.
Typical Layout Illustration. See Fig. 9 for
Condensate Drain Connection.

Specific Application Considerations | 19SM Split AH/AV Air Handler
8733826256 (2020/06)SM Split AH/AV Air Handler Subject to change without prior notice
SPECIFIC APPLICATION
CONSIDERATIONS
Well Water Systems
(Refer to Fig. 14)
In well water applications water pressure must
always be maintained in the heat exchanger. This
can be accomplished with either control valve or a
bladder type expansion tank. When using a single
water well to supply both domestic water and the
heat pump care must be taken to ensure that the
well can provide sufficient flow for both. In well
water applications a slow-closing solenoid valve
must be used to prevent water hammering.
Solenoid valves should be connected across Y1
and C1 on the interface board for all. Make sure
that the VA draw of the valve does not exceed the
contact rating of the thermostat.
Cooling Tower/Boiler Systems
(Refer to Fig. 14)
The cooling tower and boiler water loop
temperature is usually maintained between 50°F
to 100°F to ensure adequate cooling and heating
performance. In the cooling mode, heat is ejected
from the unit into the water loop. A cooling tower
provides evaporative cooling to the loop water
thus maintaining a constant supply temperature to
the unit. When utilizing open cooling towers,
chemical water treatment is mandatory to ensure
the water is free from corrosive elements. A
secondary heat exchanger (plate frame) between
the unit and the open cooling tower may also be
used.
It is imperative that all air be eliminated from the
closed-loop side of the heat exchanger to ensure
against fouling. In the heating mode, heat is
absorbed from the water loop. A boiler can be
utilized to maintain the loop at the desired
temperature.
Cooling Tower/Boiler Systems Piping
Flexible hoses should be used between the unit
and the rigid system to avoid possible vibration.
Ball valves should be installed in the supply and
return lines for unit isolation and unit water flow
balancing.
Pressure/temperature ports are recommended in
both supply and return lines for system flow
balancing. Water flow can be accurately set by
measuring the water-to-refrigerant heat
exchangers’ water-side pressure drop. (See
specification sheets for water flow vs. pressure
drop information.)
No unit should be connected to the supply or
return piping until the water system has been
completely cleaned and flushed to remove any dirt,
piping chips, or other foreign material. Supply and
return hoses should be connected together during
this process to ensure the entire system is
properly flushed. After the cleaning and flushing
has taken place, the unit may be connected to the
water loop and should have all valves wide open.
Geothermal Systems
(Refer to Fig. 14)
Closed-loop and pond applications require
specialized design knowledge. No attempt at these
installations should be made unless the dealer has
received specialized training. Using the Ground
Loop Pumping Package (GLP), makes the
installation easy. Anti-freeze solutions are utilized
when low-evaporating conditions are expected to
occur. Refer to the GLP installation manuals for
specific instructions.
NOTICE: Water piping exposed to extreme
low ambient temperatures is subject to
freezing.
Thread sealant tape should be used when
connecting to the unit to insure against
leaks and possible heat exchanger fouling.
Do not overtighten the connections.

SM Split AH/AV Air Handler
SM Split AH/AV Air Handler8733826256 (2020/06)
20 | Post-Installation System Checkout
Subject to change without prior notice
POST-INSTALLATION SYSTEM
CHECKOUT
After completing the installation and before
energizing the unit, the following system checks
MUST be made:
1. Verify that the supply voltage to the heat pump
is in accordance with the nameplate ratings.
2. Make sure that all electrical connections are
tight and secure.
3. Check the electrical fusing and wiring for the
correct size.
4. Verify that the low-voltage wiring between the
thermostat and the unit is correct.
5. Verify that the water piping is complete and
correct.
6. Check that the water flow is correct and adjust
if necessary.
7. Check the blower for free rotation, and that it
is secured to the shaft.
8. Verify that vibration isolation has been
provided.
9. Ensure the unit is serviceable.
10. Confirm that all access panels are secured in
place.
SYSTEM OPERATION
UNIT START-UP
1. Place the UPM board in “Test” mode.
2. Set the thermostat to the highest setting.
3. Set the thermostat system switch to “COOL”
and the fan switch to the “AUTO” position. The
reversing valve solenoid should energize. The
compressor should not run.
4. Reduce the thermostat setting approximately
five degrees below the room temperature.
5. Verify the heat pump is operating in the cooling
mode.
6. Turn the thermostat system switch to the
“OFF” position. The unit should stop running
and the reversing valve should de-energize.
7. Leave the unit off for approximately five
minutes to allow for system equalization.
8. Turn the thermostat to the lowest setting.
9. Set the thermostat switch to “HEAT.”
10. Increase the thermostat setting approximately
five degrees above the room temperature.
11. Verify the heat pump is operating in the heating
mode.
12. Set the thermostat to maintain the desired
space temperature.
13. Check for vibrations, leaks, etc.
SEQUENCE OF OPERATION
(See Fig. 12 Wire Schematic)
Cooling Mode
Energizing the “O” terminal energizes the unit
reversing valve thus placing the unit into cooling
mode. The fan motor starts when the “G” terminal
is energized.
When the thermostat calls for first-stage cooling
(Y1) the loop pump or solenoid valve, if present, is
energized and the first stage of the compressor
capacity starts.
DANGER: Ensure the cabinet and electrical
box are properly grounded.
IMPORTANT:
• Always check incoming line-voltage power
supply and secondary control voltage for
adequacy. Transformer primaries are dual
tapped for 208 and 230 volts. Connect the
appropriate tap to ensure a minimum
secondary control voltage of 18 volts. 24
volts is ideal for best operation.
• Long-length thermostat and control wiring
leads may create voltage drop. Increase
wire gauge or up-size transformers may be
required to ensure minimum secondary
voltage supply.
• Bosch recommends the following
guidelines for wiring between a thermostat
and the unit: 18 AWG up to 60 foot, 16
AWG up to 100 ft and 14 AWG up to 140 ft.
• Do not apply additional controlled devices
to the control circuit power supply without
consulting the factory. Doing so may void
equipment warranties.
• Check with all code authorities on
installation criteria including condensate
disposal/overflow protection criteria.
The fan motor takes 30 seconds to ramp up
to operating speed and will run at the
fan-only rated airflow, as long as there is no
call for compressor or heater operation.