A.O. Smith 120 through 250 Series Anleitung zur Verwendung

Service Handbook

PRINTED IN THE U.S.A 0510 318349-000

SERVICING SHOULD ONLY BE PERFORMED BY A QUALIFIED SERVICE AGENT.

COMMERCIAL GAS WATER HEATERS

INSTALLATION CONSIDERATIONS - PRE SERVICE

CHECKS - WATER HEATER CONSTRUCTION -

OPERATION & SERVICE - TROUBLESHOOTING

500 Tennessee Waltz Parkway

Ashland City, TN 37015

INSTALLATION CONSIDERATIONS - PRE SERVICE

CHECKS - OPERATION & SERVICE -TROUBLESHOOTING

MODEL BTR 500/A SERIES 120/121

Servicing should only be performed by a Qualiﬁed Service Agent

INTRODUCTION............................................................3

Qualifications ...........................................................3

Service Warning........................................................3

Service Reminder .....................................................3

REQUIREMENTS...........................................................4

Instruction Manual ....................................................4

Tools Required..........................................................4

Tools Optional ...........................................................4

INSTALLATION CONSIDERATIONS .............................5

Water Piping .............................................................5

Closed Water Systems........................................5

Thermal Expansion .............................................5

Gas Pressure Requirements ....................................5

Air Requirements ......................................................6

Air Supply............................................................6

Insufficient Make-up Air, Negative Air Pressure,

and Downdrafts...................................................7

Make-up Air: Direct Communication with Out-

doors ...................................................................8

Contaminated Air ................................................9

Clearances (Water Heater).......................................9

Clearances (Exterior)..............................................10

Venting....................................................................11

OPERATION AND SERVICE .......................................12

Sequence of Operation...........................................12

Electrical Sequence ................................................13

Wiring Diagram .......................................................14

Operating Sequence - Flow Chart ..........................15

Gas Control Valve..................................................16

Measuring Gas Pressures ................................16

Manifold Pressure Adjustment ..........................17

Main Valve Solenoid Connections ....................17

COMMERCIAL GAS WATER HEATER

SERVICE MANUAL

TABLE OF CONTENTS

Gas Control Valve/Burner Area View......................18

Blower Prover Switch - Settings .............................19

Thermostat and Ignition control Board View...........20

White Rodgers Integrated Control - Thermostat.....21

White Rodgers Ignition Control Board ....................21

Pre-Service Checklist .............................................22

TROUBLESHOOTING .................................................23

Ignition Control Board: Error Codes........................23

1 Flash ..............................................................23

2 Flashes ..........................................................23

3 Flashes ..........................................................24

4 Flashes ..........................................................24

6 Flashes ..........................................................24

7 Flashes ..........................................................24

8 Flashes ..........................................................25

Continuous Flash ..............................................25

Continuous On ..................................................25

Integrated Heater Control: Display Lights ..............26

Test 1: 120 VAC to Heater Check ...........................27

Test 2: Polarity Check.............................................28

Test 3: Continuity Check of High Limit (ECO).........29

Test 4: Upper Temperature Probe

Continuity Check.....................................................30

Test 5: Calling for Heat - No Blower Operation.......31

Test 6: Blower On, No Ignition ................................32

Test 7: Blower On, Blower Prover Switch Closed,

No Igniter Operation ...............................................33

Test 8: Igniter Heats, No Main Burner.....................34

Test 9: Igniter Heats, No Main Burner.....................35

Test 10: Main Burner Ignition for Less than

Five Seconds ..........................................................36

Test 11: Water Heater Shutting Off Below Setting ..37

Servicing should only be performed by a Qualiﬁed Service Agent

INTRODUCTION

This Service Manual is designed to be an aid in servicing and troubleshooting A. O. Smith

Master-Fit models BTR 500 Series 120/121 commercial water heaters. The instructions

and illustrations contained in this service manual will provide you with troubleshooting

procedures to verify proper operation and to diagnose and repair common service

problems.

This Service Manual does not replace or supersede the instruction manual that came with

the water heater. Always refer to the instruction manual that came with the water heater for

complete installation instructions. If the instruction manual is not available, copies can be

obtained from the manufacturer’s web site or by calling the toll free phone number shown

on the back cover of this service manual.

QUALIFICATIONS

Servicing the products referenced in this manual requires the ability (in the field involved)

equivalent to that of a Qualified Service Agent as defined by the American National Standards

Institute (ANSI) below. Installation skills such as plumbing, air supply, venting, gas supply,

electrical supply are required in addition to diagnostic and electrical testing skills.

ANSI Z223.1 2006 Sec. 3.3.83: “Qualified Agency” - “Any individual, firm, corporation or

company that either in person or through a representative is engaged in and is responsible

for (a) the installation, testing or replacement of gas piping or (b) the connection,

installation, testing, repair or servicing of appliances and equipment; that is experienced in

such work; that is familiar with all precautions required; and that has complied with all the

requirements of the authority having jurisdiction.”

SERVICE WARNING

If you are not qualified (as defined by ANSI above) and licensed or certified as required by

the authority having jurisdiction to perform a given task, do not attempt to perform any of

the procedures described in this manual. If you do not understand the instructions given in

this manual, do not attempt to perform any procedures outlined in this manual.

SERVICE REMINDER

When performing any troubleshooting step outlined in this service manual, always consider

the wiring and connectors between components. Perform a close visual inspection of all

wiring and connectors to and from a given component before replacement. Ensure wires

were stripped before being crimped in a wire connector, ensure wires are crimped tightly in

their connectors, ensure connection pins in sockets and plugs are not damaged or worn,

ensure plugs and sockets are mating properly and providing good contact.

Failure to perform this critical step or failing to perform this step thoroughly often results in

needless down time, unnecessary parts replacement, and customer dissatisfaction.

Servicing should only be performed by a Qualiﬁed Service Agent

REQUIREMENTS

INSTRUCTION MANUAL

Have a copy of the instruction manual that came with the water heater on hand for the

model being serviced. Instruction manuals can be obtained at the A. O. Smith web site

(www.hotwater.com) or by calling technical support at 800 527-1953.

Installation information given in this service manual is not a complete installation instruction.

Installation information covered in this service manual has a limited focus as it applies

to servicing the water heater. This Service Manual does not replace or supersede the

instruction manual that came with the water heater. Always refer to the instruction manual

that came with the water heater for complete installation instructions.

TOOLS REQUIRED

Phillips head screwdriver•

standard screwdrivers•

3/8 and 7/16 inch open end wrench•

set of marked drill bits•

electrical multimeter tester capable of measuring continuity, AC voltage, and DC voltage•

gas pressure gauge or manometer (gauge - AOS pt. no. 9005033105)•

water pressure gauge (AOS pt. no. 9004792105)•

thermometer (AOS pt no. 9005423105 - range 0 - 220 degrees F)•

1/2 inch socket with extension for removal of the clean out cover•

1-1/16 inch socket with extension for anode removal•

TOOLS OPTIONAL

Two digital manometers range -20.00 to +20.00” W.C., resolution 0.01” W.C.•

Recommend UEI model EM200, TPI model 620 or equivalent.

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

Installation information given in this service manual IS NOT a complete installation

instruction. Installation information covered in this service manual has a limited focus as

it applies to servicing. This service manual does not replace or supersede the Instruction

Manual that came with the water heater. Always refer to the instruction manual that came

with the water heater for complete installation instructions.

If the instruction manual that came with the water heater is not on hand, copies can be

obtained from the manufacturer’s web site or by calling the toll free phone number shown

on the back cover of this service manual.

WATER PIPING

Closed Water Systems

Water supply systems may, because of code requirements or such conditions as high line

pressure, among others, have installed devices such as pressure reducing valves, check

valves, and back flow preventers. Devices such as these cause the water system to be a

closed system.

Thermal Expansion

As water is heated, it expands (thermal expansion). In a closed system, the volume

of water will grow when it is heated. As the volume of water grows, there will be a

corresponding increase in water pressure due to thermal expansion. Thermal expansion

can cause premature tank failure (leakage). This type of failure is not covered under the

limited warranty. Thermal expansion can also cause intermittent temperature-pressure relief

valve operation: water discharged from the valve due to excessive pressure build up. This

condition is not covered under the limited warranty. The temperature-pressure relief valve is

not intended for the constant relief of thermal expansion.

A properly sized thermal expansion tank should be installed on all closed systems to control

the harmful effects of thermal expansion. Contact a local Qualified Service Agency (page 3)

to have a thermal expansion tank installed.

GAS PRESSURE REQUIREMENTS

Table 1 shows supply and manifold gas pressure requirements for BTR 500/A 120 - 121

model water heaters. Supply gas pressure is the pressure of fuel gas being supplied to the

water heater. Manifold gas pressure is the pressure of the gas being supplied to the water

heater’s burners.

Supply gas pressure should be measured twice. One measurement while the water

heater is not firing (static) and again while the water heater is firing (dynamic). If the

supply gas pressure drops more than 1.5” W.C. between the static and dynamic pressure

measurements, this may indicate the gas line and/or gas regulator to the water heater is

undersized. See the gas line requirements in the Instruction Manual that came with the

water heater.

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

AIR REQUIREMENTS

Carefully review the requirements for combustion and ventilation air in the instruction

manual that came with the water heater. Failure to meet these requirements when the

water heater is installed or overlooking their importance when servicing the water heater

often results in operational problems (some are listed below), needless down time,

unnecessary parts replacement, and customer dissatisfaction.

Ensure additional air for combustion and ventilation is provided when additional gas fired

appliances are installed to increase hot water supply in an existing location.

Air Supply

Stoichiometric or theoretical complete combustion requires 10 cubic feet of air per 1,000

BTUH of gas supplied. The National Fuel Gas Code also recommends an additional 2.5

cubic feet of “excess” air. For information on minimum make-up air opening sizes for

various building installations, refer to the National Fuel Gas Code NFPA 54, ANSI Z223.1.

Figure 1

Table 1

NATURAL GAS PROPANE (LP) GAS

‡Maximum Supply Gas Pressure 10” W.C. (2.49 kPa) 12” W.C. (2.99 kPa)

†Minimum Supply Gas Pressure 5.2” W.C. (1.29 kPa) 11” W.C. (2.74 kPa)

*Manifold Gas Pressure 3.5” W.C. (0.87 kPa) 10” W.C. (2.49 kPa)

‡ Maximum supply pressure; readings are taken while gas is not ﬂowing (static pressure) AND while gas is ﬂowing (dynamic pressure).

Supply pressure must never exceed this maximum value.

† Minimum supply gas pressure; readings are taken while gas is not ﬂowing (static pressure) AND while gas is ﬂowing (dynamic

pressure). Supply pressure must never fall below the minimum values. Supply gas pressures should be measured with all gas ﬁred

appliances conencted to a common main ﬁring at full capacity. If supply pressure drops more than 1.5” W.C. as gas begins to ﬂow,

the supply gas system (gas line/regulator) may be restricted or undersized. See the instruction manual for more information.

* Manifold gas pressure; reading can only be taken while gas is ﬂowing. Reading taken should be ± 0.3” W.C. of the listed value.

These water heaters are certiﬁed for use without modiﬁcation for altitudes up to 10,000 feet. For elevations above 10,000 feet

(3,048 meters), see High Altitude Installations section of instruction manual.

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

Insufficient Make-up Air, Negative Air Pressure, and Downdrafts

A lack of combustion and ventilation air can create a negative ambient air pressure in the

installed space. The vent system on one or more gas fired appliances can experience down

drafts due to the outdoor air pressure being greater than the ambient air pressure in the

installed space. Where multiple gas fired appliances are installed, one or more gas fired

appliances can “pull air” through the vent system(s) of other appliances installed nearby.

Downdraft Caused by Kitchen Vent Hood

Figure 2

One common example is in a restaurant installation where exhaust vent equipment was not

considered in sizing make-up air requirements. This condition may result in air being back

drafted by the restaurant exhaust equipment through the water heater, causing the draft

proving switch to open and/or erratic heater shutdown. See Figure 2.

Down drafts can cause poor mixing of fuel gas and combustion air in the burners.•

Down drafts can cause flue gases to spill into the installed space.•

Down drafts can cause common service problems such as ignition failure. Down drafts•

can sweep pilot gas away from the spark igniter during ignition and prevent ignition of

the pilot.

Down drafts may cause extremely dangerous conditions such as flame rollout where the•

flames from the main burner “roll out” of the combustion chamber.

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

Make-up Air: Direct Communication with Outdoors

A fresh supply of make-up air for combustion can be supplied to the water heater through

make-up air ducts, which directly communicate with the outdoors. (Not Direct Vent.)

Two openings are required: one within 12 inches of the top of the enclosure and one

within 12 inches of the bottom of the enclosure. Each opening must have a free area of

not less than 1 square inch per 4,000 BTUH of the total input of all appliances within

the enclosure. The lower opening primarily provides combustion air. The upper opening

provides vent dilution air and acts as a relief opening for flue gases should the vent become

obstructed or a downdraft condition occur.

Figure 3

Additionally, when the water heater is installed in a confined space and communicating with

the outdoor air, one permanent opening, beginning within 12 inches (30 cm) of the top of

the enclosure, must be permitted where the equipment has clearances of at least 1 inch

(2.5 cm) from the sides and back, and 6 inches (16 cm) from the front of the appliance. The

opening must directly communicate with the outdoors and must communicate through a

vertical or horizontal duct to the outdoors or spaces (crawl or attic) that freely communicate

with the outdoors, and must have a minimum free area of a) 1 square inch per 3,000 BTUH

(7cm2per 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.

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

Contaminated Air

Carefully review the warnings concerning contaminated combustion and ventilation air in the

instruction manual that came with the water heater. Combustion air that is contaminated can

greatly diminish the life span of the water heater and water heater components such as burners,

igniters, flue baffles and vent system components. Propellants of aerosol sprays, beauty shop

supplies, water softener chemicals and chemicals used in dry cleaning processes that are

present in the combustion, ventilation or ambient air can cause such damage.

Vapors from volatile compounds such as solvents, cleaners, chlorine based chemicals and

refrigerants in addition to being highly flammable in many cases, can also react to form

highly corrosive substances such as hydrochloric acid inside the water heater’s combustion

chamber. The results can be hazardous and cause product failure.

Contaminated Air Causes Aggressive Corrosion of Water Heater Components

(Burners, Igniters, Flue Baffles, Vent System, Sheet Metal Parts)

Figure 4

CLEARANCES (WATER HEATER)

A 24-inch clearance for all serviceable parts is recommended. See also Figure 5 and

Table 2. You may also refer to the instruction manual or to the label on the water heater

for clearances applicable to your specific model.

Minimum Clearances to Combustible Surfaces

Figure 5

Servicing should only be performed by a Qualiﬁed Service Agent

INSTALLATION CONSIDERATIONS

Table 2

MINIMUM CLEARANCES TO COMBUSTIBLE SURFACES

“A” - Right Side “B” - Left Side “C” - Back

5” (12.7 cm) 5” (12.7 cm) 5” (12.7 cm)

A, B, and C clearances to non-combustible surfaces is “0” inches. A 20” clearance to cover remains unchanged.

CLEARANCES (EXTERIOR)

The illustration below shows the required clearances for venting units using natural draft venting.

The vent must 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 inches in diameter or less).

Reference: NFPA 54 ANSI Z 223.1.

Figure 6

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