A.O. Smith GTS-305-NE Bedienungsanleitung

PRINTED 0709 316437-001

On-Demand Gas Tankless

Water Heater Service Manual

Service information for single and multiple unit installations

for residential, commercial, recirculation and storage tank systems.

ATI-305-N GTS-305-NI GT-305-NI

ATI-305-P GTS-305-PI GT-305-PI

ATO-305-N GTS-305-NE GT-305-NE

ATO-305-P GTS-305-PE GT-305-PE

ATI-505-N GTS-505-NI GT-505-NI

ATI-505-P GTS-505-PI GT-505-PI

ATO-505-N GTS-505-NE GT-505-NE

ATO-505-P GTS-505-PE GT-505-PE

ATI-705-N GTS-705-NI GT-705-NI

ATI-705-P GTS-705-PI GT-705-PI

ATO-705-N GTS-705-NE GT-705-NE

ATO-705-P GTS-705-PE GT-705-PE

ATI-705A-N GTS-705-NIA AGT-705-NI

ATI-705A-P GTS-705-PIA AGT-705-PI

ATO-705A-N GTS-705-NEA AGT-705-NE

ATO-705A-P GTS-705-PEA AGT-705-PE

Series 100/101 & Series 200/201

http://waterheatertimer.org/pdf/

Table of Contents

General Information................................................3-5

Specifications.........................................................6, 7

Schematic Diagrams..............................................8, 9

Fault Isolation..................................................... 10-12

Electrical Diagnostic Points

305e/o, 305i, 505e/o 505i ................................13, 14

705e/o (ASME), 705i (ASME) .........................15, 16

Wire Diagrams

305e/o, 305i, 505e/o, 505i .....................................17

705e/o (ASME), 705i (ASME) ...............................18

Flushing the Heat Exchanger .................................19

Component Replacement Instructions

Gas Control Assembly

305e/o, 305i, 505e/o, 505i ...............................20, 21

705e/o (ASME), 705i (ASME) ..........................22, 23

Fan

505e/o, 305e/o.......................................................24

305i, 505i ...............................................................25

705e/o (ASME), 705i (ASME) ...............................26

PC Board

305e/o, 305i, 505e, 505i ................................. 27, 28

705e/o (ASME ), 705i (ASME) ............................. 29

Water Flow Control Assembly

305e, 305i, 505e, 505i .................................... 30, 31

505e, 505i ....................................................... 32, 33

705e/o (ASME), 705i (ASME) .............................. 34

Heat Exchanger

305e ................................................................. 35-37

505e /o.............................................................. 38-40

305i .................................................................. 41-44

505i .................................................................. 45-49

705e/o (ASME)................................................. 50-51

705i (ASME) .................................................... 52-54

Gas Pressure Setting Procedure..................... 55, 56

Manifold Pressure Settings.................................... 57

Dip Switches............................................................ 58

On-Demand Gas Tankless Water Heater Service Manual

Key to Trade Names in this Manual:

(ASME) Indicates that the ASME models are included.

(N) Indicates Natural Gas.

(P) Indicates Propane Gas.

(e) Indicates Outdoor Models.

(i) Indicates Indoor Models.

(o) Indicates Outdoor Models.

General Information

Safety Definitions

This is the safety alert symbol. This symbol alerts you to potential hazards that can kill or hurt you and

others.

Indicates an imminently hazardous situation which, if not avoided, will result in death or

serious injury.

Indicates a potentially hazardous situation which, if not avoided, could result in death or

serious injury.

Indicates a potentially hazardous situation which, if not avoided, could result in minor or

moderate injury. It may also be used to alert against unsafe practices.

DANGER

CAUTION

WARNING

Recommended Tools

• Volt/Ohm/Amp meter with test probes

• Digital manometer or U tube type manometer with 14 inch water column (W.C.) scale, a hose and two 1/8 inch

taps

• assorted wrenches including a 3/16 Allen wrench

• assorted screw drivers including a long shafted, magnetic tipped screw driver

• leak solution or leak detector

• Teflon tape

Using this Manual

Repairs should be performed by a qualified service technician.

The following information can be referenced for additional information.

• Operation and Installation Manual

• Hot Water System Design Manual

• Technical Sheets

• Technical Bulletins

Technical Support

Visit the brand website for additional support including contact information for our Technical Service Department.

WARNING

There are a number of live tests that are required when fault finding this product. Extreme care should be used at

all times to avoid contact with energized components inside the water heater. Before checking for resistance

readings disconnect the power source to the unit and isolate the item from the circuit (unplug it).

If any of the original wire as supplied with the appliance must

be replaced, it must be replaced with type 18 AWG wire or its

equivalent.

Label all wires prior to disconnection when

servicing controls. Wiring errors can cause

improper and dangerous operation.

CAUTION

On-Demand Gas Tankless Water Heater Service Manual

General Information

On-Demand Gas Tankless Water Heater Service Manual

Service Information

The on-demand water heaters must be installed according to all local and state codes or, in the absence

of local and state codes, the “National Fuel Gas Code”, ANSI Z223.1 (NFPA 54) - current edition.

CSA American, Inc. National Fire Protection Association

8501 East Pleasat Valley Road 1 Batterymarch Park

Cleveland, OH 44131 Quincy, MA 02269

Check your phone listings for the local authorities having jurisdiction over your installation.

Massachusetts code requires this water heater to be installed in accordance with Massachusetts Plumbing

and Fuel Gas Code 248 CMR Section 2.00 and 5.00.

Water Temperature Regulation

For systems with storage tanks, the water

temperature in certain situation may vary up

to 30°F (16.7°C) higher or lower at the point

of use such as, bathtubs,showers, sink, etc.

HOTTER WATER CAN SCALD: Water heat-

ers, are intended to produce hot water. Water

heated to a temperature which will satisfy

space heating, clothes washing, dish wash-

ing, and other sanitizing needs can scald and

permanently injure you upon contact. Some

people are more likely to be permanently in-

jured by hot water than others. These include

the elderly, children, the infirm, or physically/

mentally handicapped. If anyone using hot

water in the home fits into one of these

groups or if there is a local code or state law

requiring a certain temperature water at the

hot water tap, then you must take special

precautions.

Water temperature over 125°F can cause

severe burns instantly or death from scalds.

Children, disabled and elderly are at highest

risk of being scalded.

Feel water before bathing or showering.

Temperature limiting valves are available.

WARNING

Temperature

Settings

Time to Produce 2nd & 3rd

Degree Burns on Adult Skin

160°F (71°C)

About 1/2 second

150°F (66°C) About 1-1/2 seconds

140°F (60°C) Less than 5 seconds

130°F (54°C) About 30 seconds

120°F (49°C) More than 5 minutes

80°F (27°C) - - - - - - - - - - - - - - - -

Table “A”

NOTE: This water heater must be installed according to all local and state codes or, in the absence

of local and state codes, the “National Fuel Gas Code”, ANSI Z223.1(NFPA 54)-current edition.

In addition to using the lowest possible temperature setting that satisfies your hot water needs, a means

such as a mixing valve, should be used at hot water taps used by these people or at the water heater.

Mixing valves are available at plumbing supply or hardware stores. Follow manufacturer’s instructions for

installation of the valves. Before changing the factory setting on the thermostat see Table “A”. Using the

lowest hot water temperature that meets your needs will also provide the most energy efficient operation

of the water heater.

Never allow small children to use a hot water

tap, or to draw their own bath water. Never

leave a child or handicapped person un-

attended in a bathtub or shower.

NOTE: A water temperature range of 120°F -

140°F (49°C-60°C) is recommended by most

dishwasher manufacturers.

General Information

On-Demand Gas Tankless Water Heater Service Manual

Closed System/Thermal Expansion

CAUTION - PROPERTY DAMAGE HAZARD

As water is heated, it expands (thermal expan-

sion). In a closed system, the volume of water

will grow. As the volume of water grows, there

will be a corresponding increase in water pres-

sure due to thermal expansion. Thermal expan-

sion 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. The temper-

ature / pressure relief valve is not intended for

the constant relief of thermal expansion. This

condition is not covered under the limited war-

ranty.

A properly-sized thermal expansion tank should

be installed on all closed systems to control the

harmful effects of thermal expansion. Contact a

local plumbing service agency to have a thermal

expansion tank installed.

Hot Water

Outlet

In a closed system use a

thermal expansion tank

Cold Water

Inlet Valve Pressure Reducing

Valve with Bypass

Main Water

Supply

Cold Water Supply

to Fixture

Temperature and

Pressure Relief Valve

Discharge line

6” Max. above drain

Drain line 3/4”

ID Min.

Drain

1“ Min.

Metal Drain

Pan 1-3/4”

Depth Max.

Massachusetts:

Install a vacuum relief

in cold water line per

section 19 MGL 142

Figure 1a

Typical water piping installation

Storage

Tank

Hot Water Return Line

Explosion Hazard

If the temperature and pressure relief valve

is dripping or leaking, have a qualified

service technician replace it.

Examples of a qualified service technician

include: Licensed plumbers, authorized gas

company personnel, and authorized service

personnel.

Do not plug valve.

Do not remove valve.

Failure to follow these instructions can

result in death, or explosion.

WARNING

Temperature and Pressure

Relief Valve

For protection against excessive pressures and

temperatures, a temperature and pressure relief

valve must be installed in the opening on the

on-demand storage tank. This valve must be

design certified by a nationally recognized testing

laboratory that maintains periodic inspection of

the production of listed equipment or materials

as meeting the requirements for Releif Valves for

Hot Water Supply Systems, ANSI Z21.22. The

function of the temperature and pressure relief

valve is to discharge water in large quantities in

the event of excessive temperature or pressure

developing in the water heater. The valve’s relief

pressure must not exceed the working pressure

the water heater as stated on the data plate.

IMPORTANT: Only a new temperature and

pressure relief valve should be used with your

water heater.Do not use an old or existing valve

as it may be damaged or not adequate for the

working pressure of the new water heater.

Do not place any valve between the relief valve

and the tank.

Specifications

Model Number Temperature Range

305 15,000 - 199,000 NG

15,000 - 190,000 LP

705/705 ASME

Indoor (i)

On-Demand Gas Tankless Water Heater Service Manual

Input

Min. - Max.

(BTU)

Flow Rate Hot water capacity

@ 45°F Temp. Rise

0.6 - 5.3 GPM

(2.3 - 20.1 LPM) 5.3 GPM (20.1 LPM)

Efficiency

Rating

84%

505 15,000 - 199,000 NG

15,000 - 190,000 LP

0.6 - 8.5 GPM

(2.3 - 32.0 LPM)

7.4 GPM (28 LPM) NG

7.1 GPM (27 LPM) LP

98 -140°F (37 - 60°C) [1]

84% 98 -140°F (37 - 60°C) [2]

98 -140°F (37 - 60°C) [2]

84%

8.8 GPM (33.3 LPM)

19,000 - 237,000

NG & LP

0.6 - 9.8 GPM

(2.3 - 37 LPM)

Model Number Temperature Range

305 15,000 - 199,000

NG & LP

705/705 ASME

Outdoor (e/o)

Input

Min. - Max.

(BTU)

Flow Rate Hot water capacity

@ 45°F Temp. Rise

0.6 - 5.3 GPM

(2.3 - 20.1 LPM) 5.3 GPM (20.1 LPM)

Efficiency

Rating

83%

505 0.6 - 8.5 GPM

(2.3 - 32.0 LPM) 7.3 GPM (27.6 LPM)

98 -140°F (37 - 60°C) [1]

83% 98 -140°F (37 - 60°C) [2]

98 -140°F (37 - 60°C) [2]

83%

8.7 GPM (32.9 LPM)

19,000 - 237,000

NG & LP

0.6 - 9.8 GPM

(2.3 - 37 LPM)

15,000 - 199,000

NG & LP

Residential Series

100/101*

NOTE:

[1] Minimum activation flow is approximately 0.6 gallons/minute (2.3 liters/min). Max temperature is 160° (71° C)

with the commercial controller for commercial and hydronic applications only.

[2] Max temperature is 185 ºF (85 ºC) with the commercial controller for commercial and hydronic applications only.

*100 Series is Natural Gas

*101 Series is Propane Gas

Specifications

Model Number Temperature Range

305

Indoor (i)

On-Demand Gas Tankless Water Heater Service Manual

Input

Min. - Max.

(BTU)

Flow Rate Hot water capacity

@ 45°F Temp. Rise

0.6 - 7.5 GPM

(2.3 - 28.4 LPM)

Efficiency

Rating

84%

505 15,000 - 199,000 NG

15,000 - 190,000 LP

0.6 - 9.4 GPM

(2.3 - 35.5 LPM)

98 -140°F (37 - 60°C) [1]

84% 98 -140°F (37 - 60°C) [2]

Model Number Temperature Range

305 15,000 - 180,000

NG & LP

Outdoor (e/o)

Input

Min. - Max.

(BTU)

Flow Rate Hot water capacity

@ 45°F Temp. Rise

0.6 - 7.5 GPM

(2.3 - 28.4 LPM) 6.6 GPM (25.0 LPM)

Efficiency

Rating

83%

505 0.6 - 9.4 GPM

(2.3 - 35.5 LPM) 7.4 GPM (28.0 LPM)

98 -140°F (37 - 60°C) [1]

83% 98 -140°F (37 - 60°C) [2]

15,000 - 199,000

NG & LP

Residential Series

200/201*

NOTE:

[1] Minimum activation flow is approximately 0.6 gallons/minute (2.3 liters/min). Max temperature is 160° (71° C)

with the commercial controller for commercial and hydronic applications only.

[2] Max temperature is 185 ºF (85 ºC) with the commercial controller for commercial and hydronic applications only.

6.6 GPM (25.0 LPM)

7.4 GPM (28.0 LPM) NG

15,000 - 180,000

NG & LP

7.1 GPM (26.9 LPM) LP

*200 Series is Natural Gas

*201 Series is Propane Gas

Schematic Diagrams

Outdoor Model

(NOT PRESENT ON

ALL MODELS)

(LOCATED ON BRACKET NEAR

FAN ON SOME MODELS)

(NOT PRESENT ON

ALL MODELS)

On-Demand Gas Tankless Water Heater Service Manual

Schematic Diagrams

Indoor Model

(NOT PRESENT ON

ALL MODELS)

(NOT PRESENT ON

ALL MODELS)

(LOCATED ON BRACKET NEAR

FAN ON SOME MODELS)

On-Demand Gas Tankless Water Heater Service Manual

Fault Isolation

Some of the checks below may need to be done by a qualified service technician. Call a

service technician for any remedy that involves gas or electricity. Call a service

technician if you have any doubt or reservation about performing the remedy yourself.

WARNING

Accessing Operating Information

To display the most recent error codes press and hold the “On/Off” button for 2 seconds. While holding the “On/

Off” button press the ▲button. The last 9 error codes will flash one after the other. To exit this mode press the

“On/Off” and ▲button as before.

To display the water flow through the water heater press and hold the ▲button for 2 seconds and without

releasing the ▲button press the “On/Off” button.

To display the outlet water temperature press and hold the ▼button for 2 seconds and without releasing the ▼

button press the “On/Off” button.

Standard and Commercial Controllers

1. Water Flow Begins.

• Water Flow Sensor sends pulses to the PC

Board.

• PC Board senses flow greater than 0.6 GPM

(approximate).

• Firing Sequence begins.

2. Firing Sequence.

• PC Board monitors inlet/outlet water

temperature, temperature set point, and water

flow rate.

• Combustion fan energized. Purges combustion

chamber.

• Spark igniter begins sparking.

• Gas control valve opens to minimum fire rate.

• Flame rod proves ignition.

• Spark igniter stops sparking.

3. Normal Operation.

• PC Board monitors flame rod, fan motor

frequency, outlet water temperature, controller

temperature set point and water flow rate.

• Gas control valve modulates gas input to

required firing rate.

• Combustion fan speed is adjusted for the

required firing rate.

• Water flow control valve is adjusted as needed.

4. Shut-down Sequence.

• PC Board senses flow rate less than 0.5 gpm

(approximate).

• Gas control valve closes.

• Water flow control valve resets to standby

position.

• Combustion fan runs for a short period of time

at low speed.

5. Standby Mode.

• PC Board monitors water temperature and

remote controls.

• Freeze protection is activated as needed.

Operation

On-Demand Gas Tankless Water Heater Service Manual

The On-Demand water heater has the ability to check its own operation continuously. If a fault occurs, an error

code will flash on the display of the remote controller. This assists with diagnosing the fault and may enable

you to overcome a problem without a service call.

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