A.O. Smith APW015DW Supplement

100346577_2000604338_Rev B
Indirect Plate Water Heater
Installation & Service Manual
Double-Wall Models:
APW015DW - APW120DW
Series 100
This manual must only be used by
a qualified heating installer / service
technician. Read all instructions
before installing. Perform steps in
the order given. Failure to comply
could result in severe personal
injury, death, or substantial property
damage.
⚠WARNING
Save this manual for future reference.
LOW LEAD CONTENT

2
Hazard definitions
The following defined terms are used throughout this manual to bring attention to the presence of hazards of various risk levels or
to important information concerning the life of the product.
⚠DANGER
⚠WARNING
⚠CAUTION
CAUTION
NOTICE
DANGER indicates an imminently hazardous situation which, if not avoided, will result in death or serious
injury.
WARNING indicates a potentially hazardous situation which, if not avoided, could result in death or serious
injury.
CAUTION indicates a potentially hazardous situation which, if not avoided, may result in minor or moderate
injury.
CAUTION used without the safety alert symbol indicates a potentially hazardous situation which, if not
avoided, may result in property damage.
NOTICE indicates special instructions on installation, operation, or maintenance that are important but not
related to personal injury or property damage.
HAZARD DEFINITIONS .................................................. 2
PLEASE READ BEFORE PROCEEDING ..................... 3
THE APW -- HOW IT WORKS ........................................ 4
1. DETERMINE APW LOCATION
Before locating the appliance, check: ................................ 5
Site selection and preparation ........................................... 5
Installation clearances....................................................... 5
• APW Water Heater Clearances ................................. 6
2. PREPARE WATER HEATER
Receiving and unpacking the APW.................................... 7
Setting the unit ................................................................... 7
3. HYDRONIC PIPING
APW piping assemblies ..................................................... 8
General piping information ................................................. 8
Heating fluid and Domestic Hot Water (DHW) piping........ 8
Scalding............................................................................... 8
Hydronic piping illustrations ......................................... 9-14
4. ADJUSTMENTS
3-Way control valve adjustment....................................... 15
• Control valve calibration and status indications .. 15-16
• Manual control of 3-way valve............................. 16-17
Temperature Controller Operating Controls..................... 18
5. OPERATING INFORMATION
Sequence of operation ..................................................... 19
Electronic control overview .............................................. 19
Over-temperature control and safety features ................. 19
6. WIRING
Electrical wiring connections ............................................ 20
7. MODBUS
Installation procedure....................................................... 21
ModBus eException Codes.............................................. 22
Primary Data Tables ........................................................ 23
Memory Map .................................................................... 23
Physical Wiring................................................................. 23
Procedure to change ModBus address............................ 24
Troubleshooting................................................................ 24
8. START-UP
Introduction....................................................................... 25
Pre-operational checks and procedures .......................... 25
Initial start-up.................................................................... 25
Checking mixed inlet temperature ................................... 26
Shutting down the system................................................ 26
9. MAINTENANCE
Maintenance and annual startup...................................... 27
Periodic cleaning of heat exchanger................................ 28
Strainers - inspection and replacement ........................... 28
Oiled bearing circulators .................................................. 28
Check water heater relief valve........................................ 28
10. TROUBLESHOOTING
• Table 10A - Troubleshooting Chart - No Display ..... 29
Checking temperature sensors ........................................ 30
• Table 10B - Resistance vs. Temperature ................ 30
11. SIZING DATA
How to properly size your Indirect Water Heater.........31-38
12. DIAGRAMS
Wiring Diagram ............................................................... 39
13. REPLACEMENT PARTS LIST
When ordering replacement parts..................................... 40
Revision Notes .................................................. Back Cover
Contents

3
Indirect Plate Water Heater Installation & Service Manual
Please read before proceeding
Installer – Read all instructions, including
this manual before installing. Perform
steps in the order given.
User – This manual is for use only
by a qualified heating installer/
service technician. Refer to the User’s
Information Manual for your reference.
Have this Indirect Plate Water Heater
(APW) serviced/inspected by a qualified
service technician, at least annually.
Failure to comply with the above could
result in severe personal injury, death or
substantial property damage.
Failure to adhere to the guidelines on this
page can result in severe personal injury,
death, or substantial property damage.
When calling or writing about the APW
– Please have the APW model and serial
number from the rating label.
Consider piping and installation when
determining APW location.
Any claims for damage or shortage in
shipment must be filed immediately
against the transportation company by
the consignee.
Factory warranty (shipped with unit) does
not apply to units improperly installed or
improperly operated.
⚠WARNING
NOTICE
⚠WARNING
General information –
This instruction manual provides detailed coverage for the
Indirect Plate Water Heater (APW). Each APW is equipped
with an electronic control system specifically designed for
an electronic control valve. This control system and valve
combination can be used with all models and sizes of APW
water heaters. The APW is available in the following double-
wall heat exchanger models:
• Double-Wall Models
APW015DW, 030DW, 050DW, 070DW, 090DW,
105DW, and 120DW
A typical packaged APW water heater with a double-wall heat
exchanger is depicted on page 4.
Identical electronic control systems are used on all APW
models. This system contains a control box assembly which
includes all of the electronic circuitry for the electronic
control system. In addition, the electronic control system
includes several sensors and safety devices which provide
temperature and flow control information to the control box
circuitry. The additional devices included in the electronic
control are as follows:
• DHW Inlet Temperature Sensor (RTD)
• DHW Outlet Temperature Sensor (RTD)
• Over-Temperature Switch (With Safety Shutdown)
If desired, the ModBus communication option permits the
electronic control system to be externally controlled by an
Energy Management System (EMS), Building Automation
System (BAS), or computer supplied by other manufacturers.

The APW - How it works...
1. Control valve
The 3-way electronic control valve is powered by 24 VAC
which is received from the electronic control system control
box. The temperature controller in the control box supplies
a 0 - 10 VDC control signal to precisely modulate the 3-way
valve to accurately control the temperature of the DHW
output to the desired set point.
2. System water outlet
ANSI flanged connections (2", 3", or 4" depending on model
size) with carbon steel piping that returns boiler water back to
the system loop.
3. System water inlet
ANSI flanged connections (2", 3", or 4" depending on model
size) with carbon steel piping that receives boiler water from
the system loop.
4. P & T Relief valve
Protects the heat exchanger from an over pressure condition.
The relief valve provided with the unit is set at 150 psi and
210°F.
5. Electronic control system control box
Contains a control box assembly which includes all of the
electronic circuitry for the electronic control system. In
addition, the electronic control system includes several sensors
and safety devices which provide temperature and flow control
information to the control box circuitry.
6. DHW inlet
ANSI flanged connections (2" or 3" depending on model size) with
stainless steel piping that receives cold water from the DHW
piping.
7. DHW outlet
ANSI flanged connections (2" or 3" depending on model size) with
stainless steel piping that delivers heated water back to the DHW
piping.
8. Recirculation pump
The recirculation pump helps prevent scale buildup by providing
constant recirculation through the heat exchanger on the DHW
side. It also preheats the cold water before it enters the heat
exchanger.
9. Heat exchanger
Allows water to flow between plates for maximum heat transfer
while keeping boiler water from contacting potable water.
10. Frame / skid assembly
Supports the HEX and piping while providing another method to
move and transport the unit.
4
DIR #2000577418
5
2
6
8
4
9
3
7
10
1
Typical APW Packaged Water Heater
Indirect Plate Water Heater Installation & Service Manual

5
Before locating the appliance, check:
1. Check for nearby connection to:
• Heating system water piping
• Electrical power
• DHW system water piping
2. Locate the appliance so that if water connections
should leak, water damage will not occur. When such
locations cannot be avoided, it is recommended that a
suitable drain pan, adequately drained, be installed
under the appliance. Under no circumstances is the
manufacturer to be held responsible for water damage
in connection with this appliance, or any of its
components.
3. If a new water heater will replace an existing water
heater, check for and correct system problems, such as:
• System leaks causing oxygen corrosion or heat
exchanger cracks from hard water deposits.
• Incorrectly-sized expansion tank.
• Lack of freeze protection in the appliance water
causing the system and the appliance to freeze and
leak.
⚠WARNING This appliance is certified as an indoor
appliance. Do not install the appliance
outdoors or locate where the appliance will
be exposed to freezing temperatures or to
temperatures that exceed 100°F.
Do not install the appliance where the
relative humidity may exceed 95%. Do not
install the appliance where condensation
may form on the inside or outside of the
appliance, or where condensation may fall
onto the appliance.
Installation clearances
1 Determine APW location
The heater must be installed with the prescribed clearances
for service as shown in FIG. 1-1 on page 6. The recommended
minimum clearance dimensions are listed below; however, if
local building codes require additional clearances, these codes
shall supersede the recommendations listed below:
• Sides: 24 in. (61 cm)
• Front: 24 in. (61 cm)
• Rear: 24 in. (61 cm)
• Top: 12 in. (30.5 cm)
All water piping and electrical conduit must be arranged so
that it does not interfere with the removal of the APW water
heater assemblies/parts or inhibit service or maintenance of
the unit.
Site selection and preparation
Ensure that the site selected for installation of the APW water
heater includes the following:
• Access to AC input power at 120 VAC/60 Hz
• Close proximity to system boiler loop to be used as heating
fluid source.
• If applicable, access to ModBus network wiring within the
prescribed wire lengths (see the Section 6 - Wiring)
Indirect Plate Water Heater Installation & Service Manual

1 Determine water heater location
(A)
(D)
(B)
(E)
(C)
24.00
24.00
24.00
24.00
DIR #200057741
9
Figure 1-1 APW Water Heater Clearances and Dimensions
6
Indirect Plate Water Heater Installation & Service Manual
MODEL A B C D E
APW015DW 55" 44" 15" 35.5" 10.5"
APW030DW 55" 52" 15" 35.5" 10.5"
APW050DW 55" 52" 15" 35.5" 10.5"
APW070DW 63" 61" 22" 42.5" 14.25"
APW090DW 63" 71" 22" 42.5" 14.25"
APW105DW 63" 69" 22" 42.5" 14.25"
APW120DW 63" 79" 22" 42.5" 14.25"

7
Receiving and unpacking the APW
All of the APW water heaters are shipped fully assembled and
ready for installation; therefore, installation will consist of the
following tasks:
• Unpack the APW water heater from its shipping container
• Position and secure the APW water heater at the site
• Connect the heating loop/system piping to the APW
• Connect the Domestic Hot Water (DHW) piping to the
APW
• Connect external AC power to the APW electronic
control box
• If required, connect ModBus control wiring to the
temperature controller in the electronic control box
Each APW water heater is shipped as a single crated unit.
The unit must be moved with the proper equipment (forklift,
pallet jack, etc.) to avoid possible injury to personnel or
damage to the shipping container or unit. The shipping
carton should be inspected for damage incurred during
transit prior to signing the bill of lading.
Setting the unit
APW water heaters contain two (2) round cutouts on the frame
plate and two (2) on the pressure plate of the heat exchanger
(FIG. 2-1). Use these tabs or cutouts to lift and move the unit
as specified in the heat exchanger (HEX) manual supplied with
the unit.
In multiple unit installations, it is important to plan the
position of each unit in advance. Sufficient space for piping
connections and future service/maintenance requirements must
also be taken into consideration. All piping must include ample
provisions for expansion.
FRAME PLATE CUTOUTS PRESSURE PLATE CUTOUTS
DIR #2000577418
Figure 2-1 Lifting Provisions
2 Prepare water heater
The manufacturer is not responsible
for lost or damaged freight. The freight
carrier must be notified immediately of
any damage detected.
NOTICE
Unpack the APW water heater from its shipping container
taking care not to damage the unit when cutting away the
packaging material. Remove the bolts securing the APW to
its shipping skid. Perform a complete visual inspection of the
unit to ensure there is no evidence of damage.
CAUTION While packaged in the shipping container,
the heater must be moved using a forklift
or pallet jack. After unpacking, the
heater should be lifted and moved using
the frame cutouts (double-wall model)
provided on the heater.
Indirect Plate Water Heater Installation & Service Manual

8
3 Hydronic piping
APW piping assemblies
The diameter of the piping assemblies furnished with the
water heater will depend on the size of the heat exchanger
installed in the model ordered. Smaller sized models utilize
2" piping assemblies, while all other sizes utilize 3" and 4"
piping assemblies used in each double-wall model. See Table
3A for sizing of piping assemblies used in each double-wall
model.
General piping information
In addition to the heat exchanger and piping components,
each APW piping assembly contains a number of other
important components and assemblies:
• Recirculation Pump (Continuously ON)
• Isolation
• Strainers (Boiler Water & DHW Sides)
• Blow-down Valves
• Pressure & Temperature (P & T) Relief Valve
Figure 3-1 illustrates the locations of the above mentioned
components for a double-wall heat exchanger.
ISOLA
TION VALVES
(4 PLACES)
OUTLET RTD
INLET RTD
P & T RELIEF VALV
E
BOILER WATER STRAINER
W/BLOW-DOWN VALVE
DOMESTIC WATER STRAINER
W/BLOW-DOWN VALVE
DIR #2000577647
Figure 3-1A Typical APW Piping
Heating fluid and Domestic Hot Water
(DHW) piping
The diameter of the heating fluid (hot boiler water) and DHW
piping will depend on the model number and size of the water
heater being installed. Reference Table 3A (this page) for
applicable piping sizes.
Table 3A APW Piping Assemblies
Model
Piping
Assembly
Diameter
APW015 - APW050 2"
APW070 - APW090 3"
APW105 - APW120 4"
Indirect Plate Water Heater Installation & Service Manual
Scalding
This water heater can deliver scalding temperature water at any
faucet in the system. Be careful whenever using hot water to avoid
scalding injury. Certain appliances such as dishwashers and
automatic clothes washers may require increased temperature
water. By setting the thermostat on this water heater to obtain
the increased temperature water required by these appliances,
you may create the potential for scald injury. To protect against
injury, you should install a mixing valve in the water system.
This valve will reduce point of discharge temperature by mixing
cold and hot water in branch supply lines. Such valves are
available from the local plumbing supplier.
Figure 3-1B Scald Warning
The following chart (Table 3B) details the relationship of water
temperature and time with regard to scald injury and may be
used as a guide in determining the safest water temperature for
your applications.
APPROXIMATE TIME / TEMPERATURE
RELATIONSHIPS IN SCALDS
120°F More than 5 minutes
125°F 1 1/2 to 2 minutes
130°F About 30 seconds
135°F About 10 seconds
140°F Less than 5 seconds
145°F Less than 3 seconds
150°F About 1 1/2 seconds
155°F About 1 second
Table 3B Approximate Time / Temperature Scald Chart
Anti-scald mixing valve:
Field supplied. An anti-scald mixing valve is recommended
when domestic hot water supply is above 115°F.

9
3 Hydronic piping (continued)
DIR #2000577498
BUILDING
RETURN
COLD WATER SUPPLY
HOT WATER SUPPLY
BOILER WATER IN
BOILER WATER OUT
Figure 3-2 Water to Water Heat Exchanger Single Unit
Please note that these illustrations are meant to show system piping concept only, the installer is responsible
for all equipment and detailing required by local codes.
NOTICE
Indirect Plate Water Heater Installation & Service Manual
CAUTION Mixing valves are required for the protection of low temperature loops.

10
3 Hydronic piping
DIR #2000577516
D
IR
#
2000577516
COLD WATER SUPPLY
FLOW INDICATOR
PUMP
BUILDING RETURN
BOILER WATER
IN
BOILER
WATER
OUT
EXPANSION TANK
RELIEF VALVE
STRATIFIED HOT WATER
STORAGE TANK
TANK HEIGHT TO DIAMETER
RATIO 2:1 MIN., 3:1 PREFERRED
HOT WATER SUPPLY
TEMPERA
TURE GAUGE
Figure 3-3 Water to Water Heat Exchanger Single Unit with Stratified Tank
Please note that these illustrations are meant to show system piping concept only, the installer is responsible
for all equipment and detailing required by local codes.
NOTICE
Indirect Plate Water Heater Installation & Service Manual