A.O. Smith 120 trough 500 How to use

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
1
BTR HANDBOOK
TABLE OF CONTENTS
PAGE PAGE
Troubleshooting (continued)
Introduction 1-2 Troubleshooting the Efflkal 30-31
Wire Harness Test 32
Installation IID Module 33
Clearances 3-4 Pilot Spark 34
Air Requirements 5-9 Pilot Valve 35-36
Contaminated Air 10 Main Burner Test 37
Flammable 10 Flame Rectification 38
Gas Pressure 11 IID Module 39
Gas Valve 12 Main Gas Valve 40-41
Venting 13-15
Wiring Schematics
Natural and Propane Gas 42
Sequence of Operation
Mechanical 16 Service Charts 43
Electrical 17-18
General Questions & Answers 44
Troubleshooting
Transformer 19 Parts List 45-50
High Limit 20-21
Damper (on Standby) 22 Component Part Information 51
PC Board 22-23
Thermostat 24 Service Check List 52-53
Damper (call for heat) 25-26
Effikal Damper 27 Comments 54
Effikal Harness Test 28
Normal Operation 28-29
BTR WORKBOOK INTRODUCTION
This service handbook is designed to aid in servicing and troubleshooting A.O. Smith BTR water heaters in
the field. No duplication or reproduction of this book may be made without the express written authorization
of the A.O. Smith Water Products Company.
The following text and illustrations will provide you with a step by step procedure to verify proper installation,
operation, and troubleshooting procedures. Additional quick reference data is included to assist you in
servicing this product.
The information contained in this handbook is designed to answer common questions encountered in the
operation of the BTR product line and is not meant to be all inclusive. If you are experiencing a problem not
covered in this handbook, please contact the A.O. Smith Technical Information Department at 1-800-527-
1953 or your local A.O. Smith Water Products Company representative for further assistance. This
handbook is intended for use by licensed plumbing professionals and reference should be made to the
installation manual accompanying the product. This handbook contains supplemental information to the BTR
installation and operation manual.

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
2
Qualifications: Installation or service of this water heater requires ability equivalent to
that of a licensed tradesman in the field involved. Plumbing, air supply, venting, gas
supply and electrical testing skills are required.
Tools Required:
• Phillips head screwdriver
• standard screwdrivers
• a 3/8 and 7/16 inch open end wrench
• setofmarkeddrillbits
• an electrical multimeter tester capable of measuring continuity
• gas pressure gauge or manometer (gauge - AOS pt. no. 8099-2)
• water pressure gauge (AOS pt. no. 4798)
• thermometer (AOS pt no. 4870 - range 0 - 220 degree F)
• 1/2 inch socket with extension for removal of the clean out cover,
• 1 1/16 inch socket with extension for anode removal.
MISC: TC-043 Revision 1 vs. TC-043
Revision 1:
• Adds Additional model’s information.
• Adds cover statement this Handbook’s also a Service Handbook for many BTC Models.
• Includes Power vent kit information.
• Includes BTR/C-500 gas valve information.
• Updated Damper illustrations.
Revision2:
• Revised Part Numbers on Page 15
Revision 3:
• Adds information unique to the Efflkal damper equipped (Series 110, 111 and
Retrofit) models

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
3
INSTALLATION
This portion of the handbook will review some often overlooked installation
considerations, taking note of necessary installation requirements for the BTR 120
through 500 model heaters. The installation manual covers most of these items in detail.
Clearance to Combustibles Table
MODEL A B C
120 - 200 1” (2.54CM) 1” (2.54CM) 1” (2.54CM)
250 - 305 2” (5.08CM) 2” (5.08CM) 2” (5.08CM)
365 - 500 3” (7.75CM) 3” (7.75CM) 3” (7.75CM)
A 24 inch clearance for all serviceable parts is recommended. Clearances may vary
between BTR models – See instruction manual or the label on the heater, for clearances
applicable to your specific model.
CLEARANCES FROM COMBUSTIBLES

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
4
EXTERIOR CLEARANCE
This illustrates the exterior roof clearances for BTR units with natural draft venting. The
vent shall extend at least 3 feet above the highest point where it passes through a roof of
a building, and at least 2 feet higher than any portion of a building within a horizontal
distance of 10 feet (for vents of 12" in diameter or less). (NFPA 54 ANSI Z 223.1 SEC
7.5.2a). (Sec 7.6.2a may allow reduction to 8 feet with a “ Listed vent cap”).
"Copyright by the American Gas Association. Used by permission of the copyright holder".

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
5
AIR FOR COMBUSTION
10 CUBIC FEET OF AIR PER 1,000 BTU
Stoichiometric or theoretical complete combustion requires 10 cubic feet of air per 1000
BTUH input of the gas input. The National Fuel Gas Code also recommends an
additional 2.5 cu.ft. of "excess" air. This 12.5 cu.ft minimum supply air per 1000 BTUH
input applies to natural and propane gas models.
The National Fuel Gas Code also specifies minimum make-up air opening sizes for
various building installations. (Ref: NFPA 54, ANSI Z223.1, sec 5.3)
2.5 CU.
FT.
EXCESS
AIR
10 CU.
FT.
COMB.
AIR
+
1
1
1,
,
,0
0
00
0
00
0
0
B
B
BT
T
TU
U
U

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
6
MAKE-UP AIR
DIRECT COMMUNICATION
A fresh supply of make-up air for combustion can be supplied to the heater through
make-up air ducts which directly communicate with the out of doors. Two openings are
required - one within 12 inches of the top of the enclosure and one within twelve inches of
the bottom of the enclosure. Each opening shall have a free area of not less than 1
square inch per 4000 BTUH of the total input of all appliances within the enclosure.
The lower opening is primarily providing combustion air. The upper opening is providing
vent dilution air and acts as a relief opening for flue gases should the vent become
obstructed or a downdraft condition occur. Additionally, when the heater is installed in a
confined space and communicating with the outdoor air, one permanent opening,
commencing within 12 in. (30 cm) of the top of the enclosure, shall be permitted where
the equipment has clearances of at least 1 in. (2.5 cm) from the sides and back and 6 in.
(16 cm) from the front of the appliance. The opening shall directly communicate with the
outdoors and shall communicate through a vertical or horizontal duct to the outdoors or
spaces (crawl or attic) that freely communicate with the outdoors, and shall have a
minimum free area of:
a. 1 sq. in. per 3000 BTU per hr (7 cm2per kW) of the total input of all equipment
located in the enclosure, and
b. Not less than the sum of the areas of all vent connectors in the confined space.
1 Square
Inch Per
4,000
BTUH

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
7
MAKE-UP AIR
VERTICAL DUCTS
Often it is more practical to install vertical make-up air ducts to the out doors. Again, two
openings are required - one within 12 inches of the top of the enclosure and one within
twelve inches of the bottom of the enclosure. Each opening shall have a free area of not
less than 1 square inch per 4000 BTUH of the total input of all appliances within the
enclosure.
1 Square
Inch Per
4,000
BTUH

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
8
MAKE-UP AIR
HORIZONTAL DUCTS
When the heater is installed in an interior room with no roof access for vertical ducts,
horizontal make-up air ducts should be installed. When using horizontal ducts, two
openings are required - one within 12 inches of the top of the enclosure and one within
twelve inches of the bottom of the enclosure. Each opening shall have a free area of not
less than 1 square inch per 2000 BTUH of the total input of all appliances within the
enclosure.
1 Square
Inch Per
2,000
BTUH
Dail
y
Schedule

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
9
INSUFFICIENT MAKE-UP AIR
BACKDRAFT
Insufficient make-up air is a major cause of combustion problems. One common example
is in a restaurant installation where exhaust vent equipment was not considered in sizing
make-up air requirements. This may result in air being backdrafted by the restaurant
exhaust equipment through the heater causing flue gas spillage, flame roll out, improper
combustion, inconsistent pilot operation, and/or erratic heater shut down.

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
10
CONTAMINATED AIR
Along with adequate make-up air, the quality of the air is important. Contaminants in
combustion air can lead to premature heater failure. Vapors from bleaches, soaps,
waxes, salts, etc. are drawn into the combustion chamber with the make-up air and, once
fired, mix with water vapor in the gases to form extremely corrosive hydrochloric or
hydrofluoric acid and other corrosive byproducts.
AIR FOR COMBUSTION
Flammable Items
Flammable items, pressurized containers or any other potentially hazardous articles must
never be placed on or adjacent to the heater. Open containers of flammable material
should not be stored or used in the same room with the heater.

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
11
GAS PRESSURE REQUIREMENTS
Natural Gas Propane Gas
Maximum Supply Pressure 13.8" w.c. 13.8" w.c.
Minimum Supply Pressure 4.5" w.c. 11" w.c.
Manifold Pressure 3.5 " w.c. 10" w.c.
The supply gas pressure is normally measured at the dirt leg or at the gas pressure
tapping on the gas supply shutoff valve. This reading must be measured with 'flowing'
gas.
The manifold gas pressure is measured at the manifold pressure tap of the gas valve
when the gas is flowing.
Supply Gas
Dirt Leg
Manifold
Gas Port
Manifold
Pressure
Tap

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
12
BTR GAS VALVE
The gas valves used on all BTR water heaters are
24 volt AC combination step opening gas valves.
They incorporate the pilot valve, main valve, and gas
pressure regulators into one body. The inlet view of
the valve features a filter screen and the top knob.
The top knob is a manual on/off gas control for both
the pilot and main gas valves. When the top knob is
placed on the black mark, gas is supplied only to the
pilot valve.
On the top view, we see the pilot solenoid and
pilot and main gas regulators. The top view also
displays the “TH and “TR” terminals. The pilot
gas regulator is found under its cover screw. It is
factory preset at 3.5”w.c. but can be adjusted from
2.5 to 5 inches water column. The main gas
regulator is found under its cover screw. It is
factory preset to 3.5 inches w.c. and adjusts gas
pressure output from 2.5 to 5 inches water
column. The two electrical terminals are marked
TH and TR. The TH terminal is the common
between the pilot valve solenoid coil and the main
valve solenoid coil. The other wire emerging from
the pilot solenoid connects to the pilot valve
electrical output on the IID (terminal PV). The TR
terminal connects directly to the main valve
electrical output from the IID module
(terminal MV).
On the outlet view of the gas valve, we see the
pilot gas connection port, manifold gas connection
port, a limited bleed vent port, the manifold gas and
pressure tap.
See step 18 for BTR-500 gas valve illustration

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
13
VENTING
Atmospheric Multiple Heaters
All BTR water heaters are classified by ANSI as category I (non-condensing, negative
pressure venting) appliances. They are approved for type B vent.
For larger applications, BTR water heaters can be common vented together either in a
tapered manifold or constant size manifold. (Follow National Fuel Gas Code
requirements for sizing and installation.)
BTRs may be common vented only with other category I appliances. (See venting
section in the National Fuel Gas Code).
A minimum of ¼” rise
per foot of horizontal
vent is re
q
uired.
Chimne
y

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
14
DRAFT INDUCER
Draft inducers can be used with BTR water heaters to mechanically aid a lazy chimney in
vertical vent applications. They are not designed to allow “through-the-wall” vent
installations. (See Power Venter)
SINGLE UNIT INSTALLATION
When mechanically venting, the following items are required:
Qty Description Part No.
1 Draft Inducer (up to 300,000Btuh) 90909
1 Draft Inducer (up to 305,000 thru 500,000 Btuh) 90910
1 Draft Prover Switch 95220
1 Relay Switch 96695

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
15
POWER VENT KITS FOR SIDEWALL VENTING
Water Heater Models Part Number
BTR-120-200 193933-0
BTR-250-500 193933-1
BTR water heaters can be used
with power vent kits for sidewall
venting. A.O. Smith offers power
vent kits for use on installations with
a maximum of 100 equivalent feet
of vent piping. The power vent kits
also use type B vent materials.
When power venting, specific
exterior clearances must be
maintained, as outlined in the
National Fuel Gas Code. (NFPA
54, ANSI A223.1, sec 7.8)
Male plug
to Cable
Female plug
to Damper
40’, Power Venter
cablewith“Y”
connect

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
16
BTR SEQUENCE OF OPERATION
1. Thermostat calls for heat 2. Flue dam
p
er o
p
ens
3. Intermittent
I
g
nition Control
5. Main gas valve opens
7. Thermostat satisfies
4. Pilot gas opens,
Pilot sparks and
flame
p
roves
6. Main burner i
g
nites
8. Main and pilot
burners "OFF"
SEQUENCE OF OPERATION
To understand BTR tank type water heaters, an examination of their sequence of
operation is necessary.
When the thermostat calls for heat, the relay in the draft hood assembly activates, de-
energizing the flue damper motor. The damper opens and power flows to the IID
(Intermittent Ignition Device). This activates the IID module to open the pilot valve
and begin sparking at the pilot burner assembly. Once the pilot flame is established
and confirmed back to the IID, the sparking is stopped and the main gas valve is
opened, allowing gas flow to the main burner. When the thermostat satisfie’s, main
and pilot gas is shut off.
9. Flue dam
p
er closes

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
17
BTR ELECTRICAL SEQUENCE
100 – 109 Series

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
18
BTR ELECTRICAL SEQUENCE OF OPERATION
Motor Opens
Damper
Power to Damper
#2 Interrupted
Series 110 and 111
Effikal
Series 110 and 111
Effikal
IID Module
(24V) Receives Voltage
Module (PV) Teminal
Sends 24V to Pilot Coil
Module (Spark) Sends
10,000V Spark to Pilot
Spark Stops
Dam per Motor Energized
and Dam per Closed
Power to Damper
Relay (4) Interupted
Them ostat O pens
Main Burner Heats Tank
Module (MV)
Terminal Sends 24V
To Main Gas Coil
90 Second Trial /
5 Minute Delay Between
Trials - C on tin u ou sly
Pilot Ignites and Proves Flam e
Cam On Damper Blade
Closes Proving End Switch
Damper Spring Opens
Dam per Blade
Motor Relay Interrupts
Power to Motor
Therm ostat Closed
High Limit Closed
Tank Tem perature
Motor Closes
Damper
High Limit (ECO)
Closed
Tank Tem perature
Satisfied
24V Transform er
On / OFF Switch "ON"
120 Vac to Junction Box

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
19
TROUBLESHOOTING BTR WATER HEATERS
To troubleshoot a BTR water heater check that:
• 120 VAC is supplied to the heater
• the tank is full of water
• gas is supplied to the unit
STEP 1 TEST THE TRANSFORMER
STEP 1 - TO TEST THE TRANSFORMER - Using a multimeter, test for 24 VAC
between the secondary transformer terminals.
IF THEN
The meter does not read 24 VAC: • Check that the 120 VAC is supplied
from the On/Off Switch – if not, replace
switch.
• Check that the 120 VAC is supplied
from transformer.
The meter reads 24 VAC: • Go to step 2.