A.O. Smith 120-500 User Manual

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

BTR HANDBOOK

TABLE OF CONTENTS

PAGE PAGE

Troubleshooting (continued)

Introduction

Installation

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

Sequence of Operation

Mechanical 16 Electrical 17-18

Troubleshooting

Transformer 19 High Limit 20-21 Damper (on Standby) 22 PC Board 22-23 Thermostat 24 Damper (call for heat) 25-26

Effikal Damper 27 Comments 54 Effikal Harness Test 28 Normal Operation 28-29

1-2 Troubleshooting the Efflkal 30-31

Wire Harness Test 32 IID Module 33

Wiring Schematics

Natural and Propane Gas 42

Service Charts

General Questions & Answers 44

Parts List

Component Part Information

Service Check List

45-50

52-53

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 1-800-5271953 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

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

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 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.

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”).

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

AIR FOR COMBUSTION

10 CUBIC FEET OF AIR PER 1,000 BTU

10 CU.

FT.

COMB.

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.

2.5 CU. FT.

EXCESS

AIR

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)

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 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.

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

MAKE-UP AIR

VERTICAL DUCTS

1 Square Inch Per 4,000 BTUH

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.

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

MAKE-UP AIR

HORIZONTAL DUCTS

DailySchedule

1 Square Inch Per 2,000 BTUH

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.

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

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

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.

Supply Gas

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

GAS PRESSURE REQUIREMENTS

Manifold Pressure Tap

Dirt Leg

Manifold Gas Port

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.

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

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

A.O. Smith Water Products Service Handbook

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

VENTING

Atmospheric Multiple Heaters

Chimne

A minimum of ¼” rise per foot of horizontal vent is required.

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.O. Smith Water Products Service Handbook

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

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

A.O. Smith Water Products Service Handbook

Female plug

to Damper

40’, Power Venter cablewith“Y” connect

Male plug

to Cable

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

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)

A.O. Smith Water Products Service Handbook

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

BTR SEQUENCE OF OPERATION

9. Flue damper closes

1. Thermostat calls for heat

7. Thermostat satisfies

3. Intermittent Ignition Control

5. Main gas valve opens

2. Flue damper opens

4. Pilot gas opens, Pilot sparks and flameproves

6. Main burner ignites

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, deenergizing 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.

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