AO Smith Water Heater 120 trough 500 User Guide
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
BTR HANDBOOK  
TABLE OF CONTENTS  
PAGE  
PAGE  
Troubleshooting (continued)  
1-2  
Troubleshooting the Efflkal  
Wire Harness Test  
IID Module  
30-31  
32  
33  
Introduction  
Installation  
Clearances  
3-4  
5-9  
10  
10  
11  
Pilot Spark  
Pilot Valve  
Main Burner Test  
Flame Rectification  
IID Module  
34  
35-36  
37  
38  
39  
Air Requirements  
Contaminated Air  
Flammable  
Gas Pressure  
Gas Valve  
12  
Main Gas Valve 40-41  
Venting  
13-15  
Wiring Schematics  
Natural and Propane Gas  
42  
Sequence of Operation  
Mechanical  
16  
43  
Service Charts  
Electrical  
17-18  
General Questions & Answers  
Parts List  
44  
Troubleshooting  
Transformer  
19  
20-21  
22  
22-23  
24  
45-50  
51  
High Limit  
Damper (on Standby)  
PC Board  
Thermostat  
Damper (call for heat) 25-26  
Component Part Information  
Service Check List  
Comments  
52-53  
54  
Effikal Damper  
27  
Effikal Harness Test  
Normal Operation  
28  
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.  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
1
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
Installation or service of this water heater requires ability equivalent to  
Qualifications:  
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  
set of marked drill bits  
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.  
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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.  
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•
Revision2:  
Revised Part Numbers on Page 15  
•
•
Revision 3:  
Adds information unique to the Efflkal damper equipped (Series 110, 111 and  
Retrofit) models  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
2
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
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.  
CLEARANCES FROM COMBUSTIBLES  
Clearance to Combustibles Table  
MODEL  
120 - 200  
250 - 305  
365 - 500  
A
B
C
1” (2.54CM)  
2” (5.08CM)  
3” (7.75CM)  
1” (2.54CM)  
2” (5.08CM)  
3” (7.75CM)  
1” (2.54CM)  
2” (5.08CM)  
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.  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
3
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
EXTERIOR CLEARANCE  
"Copyright by the American Gas Association. Used by permission of the copyright holder".  
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”).  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
4
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
AIR FOR COMBUSTION  
10 CUBIC FEET OF AIR PER 1,000 BTU  
10 CU.  
FT.  
COMB.  
AIR  
1,000  
BTU  
+
2.5 CU.  
FT.  
EXCESS  
AIR  
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)  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
5
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BTR TANK TYPE HEATERS  
SERVICE HANDBOOK  
MAKE-UP AIR  
DIRECT COMMUNICATION  
1 Square  
Inch Per  
4,000  
BTUH  
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 cm2 per 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.  
A.O. Smith Water Products  
Irving, Texas ©2000  
Service Handbook  
Training Department  
6
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