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Data tag for a new AO Smith electric water heater giving serial number, model, age, other information (C) Daniel Friedman at InspectApediia.com A.O. Smith Water Heater Age, Manuals, Error Codes
AO Smith Water Heater Installation, Troubleshooting, Repair including Intelli-Vent & other Error Codes

A.O. Smith Water heater age decode key & water heater manual sources.

Age decoding guide for water AO Smith water heaters, manuals, repair & maintenance guides.

The water heater age guide on this page works for these brands: AO Smith, Glasccote, National, Perma-Glas water heaters.

We give contact information for AO Smith water heater, geyser, cylinder, calorifier manufacturers and for water heater installation, operation, & troubleshooting manuals.

We include a table of common error codes given on some models of A.O. Smith water heaters.

Our photo at page top shows an oil fired water heater with a backpressure problem and other safety concerns like a missing extension tube on that relief valve, and maybe a missing draft regulator and perhaps an oil line that is not protected from damage.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

A.O. Smith Water Heater Age Decoding Tips

A.O Smith water heater data tag (C) Daniel Friedman InspectApedia.com

Contact: A. O. Smith Corporation | 11270 West Park Place | P. O. Box 245008 | Milwaukee, WI 53224 USA, Tel: 855.424.9892

A.O. Smith Water Heaters, 500 Tennessee Waltz Parkway, Ashland City, TN 37015 USA, Tel: 1-800-433-2545 Website: www.aosmithwaterheaters.com Email: parts@hotwater.com

[Click to enlarge any image]

A.O. Smith Water Heater Age Determination - reader comment: (May 11, 2012) AO Smith employee said: To tell the age of any AO Smith water is the first 4 numbers.

The first 2 are the year and the second 2 are what week it is. I work in the Q.C. Department there and make the serial plates all the time. Hope this information helps some people out - A.O.S. employee.

Current AO Smith water heater date code

Ser# YYWW123456 example 1604123456 decodes to YY=Year=2016 and WW=Week No. 04 of that year.

However on some AO Smith water heaters, particularly older models, you'll see a confusion of letters and numbers in the serial number that may be decoded into manufacturing date as shown below.

Older AO Smith water heater date codes

Ser# YYWW123456 - example: Ser# 9902123456 decodes to year 1999 and the week 02 - or early January. This A.O. Smith water heater date of manufacture code has been used since 2008.

Ser# MMYY1234567 - example: Ser# 03991234567 decodes to March 1999 this older style AO Smith water heater date code decodes as shown where MM = month and YY = 2 digit year.

Ser# MYY1234567 - example Ser# B0112344567 decodes to February 2001: the first letter encodes the month using A - N for January - December (the letter I is not used) and the second two digits encode the year. See the Month Decoding table given below

Ser# FB00A123456 decodes to F=Factory code, B=month code using A - M for January - December (the letter I is not used) and the next two digits encode the year.
- example: Ser# GB92-03123456-789 decodes to Factory ID=G, Month=B or February, Year=92 or 1992.

Ser# N69-C-YY-12345 decodes year in the pair of digits shown as YY - found on water heaters from the 1970s

Other AO Smith water heaters that may be sold under different brand names include Glascote water heaters, National water heaters & Perma-Glas water heaters.

AO Smith
Water Heater
Age Decoder: Month Table
Letter Month
A January
B February
C March
D April
E May
F June
G July
H August
J September
K October
L November
M December

Notes to the table above

Note that to avoid confusion, the letter I is not used.

A Nano-History of A.O. Smith Water Heater Company

AO Smith was founded in 1915 and registered its first U.S. patent in 1936, for its glass-lined water heater, a tank that enjoyed a longer life by resisting corrosion and leaks. By 2006 the company had purchased both Canadian GSW Incorporated and the American Water Heater Company.

Contact Information & Service Manuals for AO Smith Water Heaters

A.O Smith water heater data tag (C) Daniel Friedman InspectApedia.comPhoto: A.O. Smith water heater data tag detail showing the water heater serial number

A.O. Smith water heaters are also sold under these brand names:

Glascote Water Heaters; PermaGlas water heaters

New AO Smith electric water heater installation (C) Daniel Friedman Poughkeepsie New AO Smith electric water heater installation (C) Daniel Friedman Poughkeepsie

Photos: Above: an A.O. Smith water heater installed, and the product packaging label data for that new AOS electric water heater.

Below: the data tag for this new A.O. Smith electric water heater.

The serial number for this A.O. Smith water heater is ME98-0041362-917

I decode this to E = May and 98 = 1998. We purchased this water heater as new old stock in 2015 - it was the last heater of this model series in stock at the local Poughkeepsie supplier.

AO Smith Water Heater Standard Error Codes

If your AO Smith condensing water heater code includes a circuit board or remote control it can show an error code. Contact your plumber or AO Smith technical support at the location given above in this article.

Watch out: your water heater model may use different codes or may provide error codes that are not given here. Therefore you'll want to consult the manual for your specific heater.

Table of AO Smith Condensing Water Heater Error Codes
Error Code Meaning
005

Improper combustion, warning for 991 error.

Watch out: this is an unsafe condition risking CO hazards.

031 Wrong dip switch setting, possibly LP gas set when the fuel is Natural gas, or vice versa
070 Computer board failure - see 701
072 False flame detected - see 721
074 Remote control problem - see 741, 751
099

Improper combustion - see 991

Watch out: this is an unsafe condition risking CO hazards.

101

Improper combustion.

Watch out: this is an unsafe condition.

Look for a blocked flue or chimney (or downdrafts in the chimney) or a problem with the draft inducer fan.

111

Ignition failure; the burners do not light.

Check for a bad igniter, flame sensor, gas valve. Check for gas supply. Check for a blown fuse on the circuit board.

121 Burner flame lost. See code 111 above.
311

Output thermistor failure.

Check the thermistor and its wires on the heat exchanger. Replace the thermistor if you don't see a loose or disconnected wire.

321

Input thermistor failure.

Check the thermistor and its wires at the water inlet. Replace the thermistor if you don't see a loose or disconnected wire.

391

Air-fuel ratio rod failure.

Check wire connections and if no loose wire, replace the AFR rod.

441

Inlet filter clogged, water flow problem.

Also check for loose wire connections.

510 Gas valve failure. Inadequate gas pressure or flow.
551

Gas solenoid valve failure.

Check gas supply and if no problem the solenoid needs replacement.

661

Water heater fan motor failure.

Check for loose wires and if none found the fan needs replacement.

701

Computer board failure;

check for loose wires, electrical power supply, signs of damage to the board such as black or brown marks indicating overheating or burned

711

Gas solenoid valve drive circuit failure.

See Codes 111 & 121
721

False flame detected. Blinks 6 times.

Check for condensate accumulation, blocked or missing condensate drain, condensate leaks.

741

Remote control not communicating with the water heater, check remote batteries,

check remote sensor wiring, remote control access line of sight.
751 Remote control not communicating with the water heater, check remote batteries, line of sight.
761

Easy Link system communication failure.

Check connection between multiple water heaters.

991

Improper gas combustion. Blinks 5 times.

Watch out: this is an unsafe condition risking CO hazards.
If this indicator is on from first activation of the heater it may not be properly adjusted for the elevation at which the heater is installed.

Check for blocked exhaust flue or under-sized exhaust flue.

Check for debris clogging the gas burner or for a failed or blocked fan.

How to use the A.O. Smith water heater error code table above

Data tag for a new AO Smith electric water heater giving serial number, model, age, other information (C) Daniel Friedman at InspectApediia.com

AO Smith Water Heater Manuals, Error Code Charts, Troubleshooting Guides

AOS Intelli-Vent error code example - the full PDF download is given here at InspectApedia.com

Above: an excerpt from the AOS Intelli-Vent heater error code chart given in PDF form just below.

Also see AO Smith water tanks & well tanks:

AO Smith Electric Water Heater Manuals

AO Smith Gas Water Heater Manuals

Question: troubleshooting the Combustion Chamber Temperature Sensor - TCO thermal switch on an AO Smith Water Heater

(Apr 9, 2018) john said:
Hello, I have a bit of a situation on my hands and I would really appreciate some help. Our Promax Plus water heater suddenly stopped working a few days ago so we ran to lowes and purchased a universal thermocouple.

When we took out the old thermocouple I noticed that it had a TCO while the universal one did not, no big deal i thought so i installed the new universal thermocouple and the pilot fired right up, literally.

This was yesterday. Well for the rest of the day the heater stayed on, again literally, but i figured it was normal since it was a new thermocouple. Fast forward to today and the furnace was still turned on. Turned on like when someone is taking a shower or is using hot water. Now i know this isnt normal and very dangerous so we turned off the heater and turned the gas to off.

So to summarize the heater stayed on after we replaced the thermocouple with a universal one with no TCO. Could the lack of a TCO in the new thermocouple have caused this or is it something else?

Reply: TCO Temperature Cut-Off thermal reset switch on an A.O. Smith Water Heater.

AO Smith water heater thermal cutdoff control switch at InspectApedia.com Combustion Chamber Temperature Sensor TCOBelow is A.O. Smith corporation's description of their thermal cutoff sensor on the thermocouple:

COMBUSTION CHAMBER TEMPERATURE SENSOR - The C3 Technology water heaters will come equipped with a thermal cutoff (TCO) device that is integral with the thermocouple. Temperature cutoff points range from 160°C to 200°C depending on model. The TCO is an automatic reset thermal switch.

When activated it will open the thermocouple circuit and shut off the main and pilot burner gas flow. The pilot would have to be relit after the TCO has had sufficient time to cool down (sensor is below 120 degrees F).

The TCO performs two primary functions:

• In the event of flammable vapor ignition inside the combustion chamber, it senses the corresponding increase in temperature and shuts off gas flow to the main and pilot burners.

• If excessive temperatures inside the combustion chamber indicate poor combustion due to a clogged LDO screen or inadequate air for combustion, the TCO will shut off gas flow to the main and pilot burners.

John, from the above you'll see that the absence of a TCO on a thermocouple would not be likely to force a burner to stay on. I think more-likely the thermocouple you installed is defective or is not properly installed. I've found, for example, occasional operating problems when the end of the thermocouple that screws into the gas valve is not properly seated.

Watch out: The situation you describe is unsafe. I would leave the heater off pending proper repair.

Reader follow-up:

I really appreciate your response. The heater has been off since yesterday and wont be turned on again until the problem is fixed. The installation itself was actually something that I was going to double check.

Someone suggested the thermostat be replaced, is a faulty thermostat a possibility? This seems unlikely since it was working fine before.

Reply: details of the TCO on an AOS water heater

(Apr 10, 2018) (mod) said:
John

When a gas fired water heater burner won't turn OFF indeed I suspect a bad temperature sensor or thermostatic control. That's because the thermocouple has a more narrowly-defined job: confirming that there is a proper gas flame. The thermocouple is intended to shut OFF the burner IF there is no gas flame - so as to avoid continuing to pour explosive gas, un-ignited, into the building.

It's a safety device focused on proper gas ignition.

If your burner has GOT proper ignition and is burning on continuously, AND if no hot water is being taken out of the tank, it'd make sense to look for a bad thermostatic control.

What's troubling of course is that I inferred from your question that previously the heater was not turning ON and you had no hot water.

Below is a photo of AO Smith's 160 deg TCO.

Also see this AO SMITH GAS & ELECTRIC WATER HEATER SERVICE MANUAL [PDF] at inspectapedia.com/plumbing/AO-Smith-Gas-Electric-Water-Heater-Service-Manual.pdf retrieved 2018/04/10, original source: AO Smith www.hotwater.com/lit/training/320991-000.pdf

...


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2022-07-08 by InspectApedia-911 (mod)

@Anonymous,

That sounds right to me. I will review our sources to see if serial number starting with S have a different decoding.

On 2022-07-07 by Anonymous

A.O.Smith ProMax 40 Gallon water heater. Model# JW40NVH-ES-02, Cat # 9211814001.

Trying to identify the age, but confused about the serial# chart. Serial# S1020 F002714

Your chart goes A-M, but this model starts with "S", which I don't see in the charts. Assuming it's the 20th week of 2010, but want to double check.

On 2022-06-20 by InspectApedia (mod) - longlasting 1972 A.O. Smith

@Mike Marcoe,

Thanks for nice photo of your data tag and giving us the serial number. Using the Months table above on this page, I would say that the M stands for December and the 72 is for the year 1972.

So yes, it could very well be original to the home. Nice long life.

On 2022-06-20 by Mike Marcoe

My serial number is 800-M-72-09519 Model number is KGA 40 800

The home was built in 1972. Could this be an original?

It was replaced just this morning due to a leak and some corrosion. See attached image for a screenshot.

Mike Marcoe

1972 A.O. Smith water heater (C) InspectApedia.com Mike

On 2022-03-02 by Inspectapedia Com Moderator

@Lolita Smith,

I'm assuming you have an AO Smith water heater since you're on this page. If so, please see the decoding example and corresponding table shown above on this page:

Example:
Ser# FB00A123456 decodes to F=Factory code, B=month code using A - M for January - December (the letter I is not used) and the next two digits encode the year.

So your serial number indicates: M=Factory code, C=March, and the 00= the year 2000.

On 2022-03-02 by Lolita Smith

Trying to determine the age of my water heater. Thank you. My serial number is: MC00-0017367-S71

On 2021-10-20 by inspectapedia.com.moderator

@Steve Smith,

Using the information and examples above on this page, that serial number would be January of 2000. The A is for the month and the 00 are the year.

How old is the house where this heater is installed? What are the country and city? Are there any service tags or is there a manual with the heater (and what's the publication date of the manual?)

Please attach a photo of the data tag

On 2021-10-20 by Steve Smith

My serial # is - MA 00150665-917 it is AO Smith When was my water heater built ? qcmarketing@comcast.net

On 2021-05-16 by danjoefriedman (mod)

@Erika Beattie, The serial number for this A.O. Smith water heater is ME98-0084152-H43

I decode this to E = May and 98 = 1998.

On 2021-05-16 by Erika Beattie

Trying to find the age of my water heater. ser number: ME98-0084152-H43 model: ELJF. 40. 917

A.O. Smith water heater (C) InspectApedia.com Erika

On 2021-03-24 by danjoefriedman (mod)

@Rhonada Pierson,

Start with a note of your building age so you know which of the decoders given at page top is most likely to be right

Current AO Smith water heater date code
Ser# YYWW123456 example 1604123456 decodes to YY=Year=2016 and WW=Week No. 04 of that year.

However on some AO Smith water heaters, particularly older models, you'll see a confusion of letters and numbers in the serial number that may be decoded into manufacturing date as shown below.

Older AO Smith water heater date codes
Ser# YYWW123456 - example: Ser# 9902123456 decodes to year 1999 and the week 02 - or early January. This A.O. Smith water heater date of manufacture code has been used since 2008.

Ser# MMYY1234567 - example: Ser# 03991234567 decodes to March 1999 this older style AO Smith water heater date code decodes as shown where MM = month and YY = 2 digit year.

Ser# MYY1234567 - example Ser# B0112344567 decodes to February 2001: the first letter encodes the month using A - N for January - December (the letter I is not used) and the second two digits encode the year.

Ser# FB00A123456 decodes to F=Factory code, B=month code using A - N for January - December (the letter I is not used) and the next two digits encode the year.
- example: Ser# GB92-03123456-789 decodes to Factory ID=G, Month=B or February, Year=92 or 1992.

Ser# N69-C-YY-12345 decodes provide year in the pair of digits shown as YY - found on water heaters from the 1970s

On 2021-03-24 by Rhonada Pierson

How old is my hot water heater serial number 0903J005524.

On 2020-11-06 by danjoefriedman (mod)

Thanks for the query, Jerry, sorry I don't have the details about which gas regulators are used in your old AOS boiler.

But if you don't have the old gas regulator whose specs you could read, you can surely get that from AO Smith's technical support

Contact: A.O. Smith Water Products, A. O. Smith Water Products 500 Tennessee Waltz Parkway Ashland City, TN 37015 USA, Tel: 800-527-1953.

On 2020-11-02 by Jerry

i have an old A.O Smith cast iron 6-19G natural gas water boiler &, i need to know what is the proper gas valve regulator to work well with it? Btu input is 238.000 & the output is 190.000

On 2020-09-15 - by (mod) -

James

SEARS KENMORE WATER HEATER AGE & MANUALS should be more accurate than a mere guess of Aug 1997 - see

https://inspectapedia.com/plumbing/Sears-Kenmore-Water-Heater-Age-Manuals.php

On 2020-09-15 by james Bique

Have a Kenmore Power Miser 6 Model 220.394100 serial# S 0897C11602 what is the year of manufacturing?

On 2020-09-01 by ted friedberg

what is age of my ao smith water heater Model ELJ40 S# AEB308165-Z99

On 2020-08-31 by Maureen

How old is my water heater? Thank you

On 2020-04-10 - by (mod) -

As your serial number format doesn't exactly match the examples we've found for de-coding AOS water heater age,
a guess is

AD6A067772

Ser# FB00A123456 decodes to F=Factory code, B=month code using A - N for January - December (the letter I is not used) and the next two digits encode the year.
- example: Ser# GB92-03123456-789 decodes to Factory ID=G, Month=B or February, Year=92 or 1992.

so AD - D = April and 06 = 2006

Let's do a sanity check: how old is the house where this heater is installed? What are the country and city? Are there any service tags or is there a manual with the heater (and what's the publication date of the manual?)

Please attach a photo of the data tag

On 2020-04-10 by Charlotte Skipper

Our water heater (electric) has serial number AD6A067772. What is the age, please?
Thanks!

On 2020-02-21 - by (mod) -

Can't say Rosemarie as we have not a shred of data, just six words of text.

But if your water heater is an AO Smith unit, take a look at the data tag on your heater, find the serial number, then compare it's format and characters with the AO Smith water heater decoding guides given above on this page.

You are also welcome to try the "add image" button to post a photo of your heater's data tag.

Knowing the country, city, and age of the home are also useful.

On 2020-02-21 by Rosemarie Grimmell

How Old is this water heater?

On 2019-11-16 - by (mod) -

Jack,

AO Smith water heater age decoders are given on the page above.

Your format SN # F06A147109 looks closest to this decoding example given above
Ser# FB00A123456 that's explained in the article, as

Ser# FB00A123456 decodes to F=Factory code, B=month code using A - N for January - December (the letter I is not used) and the next two digits encode the year.
- example: Ser# GB92-03123456-789 decodes to Factory ID=G, Month=B or February, Year=92 or 1992.

but it's not an exact match.

1. Is this an A.O. Smith water heater?

2. if so and if it doesn't match the known codes we can guess at 2006 or you could try asking them info@aosmith.nl

3. Let's have a "sanity check" - what are the country and city of your water heater and what is the age of the building where it's installed?

The company's more-recent water heater data tags encode the year as

YYWW123456 where YY = year and WW = week number from 1-52

Please attach a sharp photo of the data tag found on your water heater by using the add image button

On 2019-11-16 by Jack

Trying to figure out year of hot water heater. SN # F06A147109

On 2019-10-20 - by (mod) -

I don't know I would need more information to even make a guess. Perhaps you can attach a photo.

On 2019-10-20 by George

Installed by previous owner, no manual. Black plastic cover exploded onto floor under heater. What gives?

On 2019-10-20 by g

george

On 2019-07-19 by (mod) -

Anon

Let me know which manual you're looking at - one of ours? And that'll make it easier for me to research its publication date.

On 2019-07-19 by Anonymous

Need publication date for owners manuals. No date on manuals, but identified as part numbers 184165-003 and 320388-001.

On 2019-07-07 by Caryn

We own a AO smith has water heater. It flashes six times but no hot water. We unplugged it. It went through four cycles but then just shuts down. Any ideas?

On 2018-12-25 by (mod) - Is it better to keep the power turn on or turn it on and off to conserve electricity?

EG

You can turn off the water heater when leaving for several days or longer, and will save a little money - standby losses from modern water heaters are not very great.

Conventional wisdom is that one can reduce the cost of electric hot water, if you use hot water at fairly regularly times, by having have an electrician install an automatic timer that turns the heater off for periods when it will not be in use -

see TIMERS for ELECTRIC WATER HEATERS inspectapedia.com/Energy/Hot_Water_Heater_Timers.php

Interestingly, Elk and Auberg found that timers don't save much energy, but that where hot water use occurs at regular times, turning the heater down (or maybe off) after the last daily use can save money. Here is an excerpt:

It is apparent that for no-flow standby loss reduction, the use of a clock-timer is marginal at best~ A more appropriate test sequence would be one which represents a typical household water use pattern, allowing the tank to be de-energized prior to the final hot water use during the day. Under idealized conditions, the upper limit of savings achievable with a clock-timer would be to reduce standby losses to zero for the duration of the u"off" time by completely using the last tankful of heated water.

A more realistic limit would be to use the last tankful down to about 100degF which would reduce the temperature differential to about 30 degrees over ambient the off period.

Calvin W. Ek, P.E. and Co Douglas Auburg, PeE., CEM, ELECTRIC WATER HEATER STANDBY LOSSES: COMPARISON OF CONSERVATION STRATEGIES AND THEIR ENERGY SAVINGS, Bonneville Power Administration (un-dated), retrieved 2018/12/25, original source: aceee.org/files/proceedings/1984/data/papers/SS84_Panel5_Paper_06.pdf

Other interesting facts about standby losses of water heaters:

Gas water heaters have higher standby losses than electric water heaters as additional heat from the water tank is lost through the exhaust flue (an automagic flue damper can reduce that loss)

Larger water heater tanks, because of their larger surface area, tend to have higher standby losses.

Tankless water heaters that do not maintain any reservoir of hot water have zero standby losses.

On 2018-12-25 by EG

I have older model AO Smith electric water heater in this apartment I moved into. Is it better to keep the power turn on or turn it on and off to conserve electricity?

On 2018-08-22 by Tony

My A.O. Smith just started leaking water . serial number 75167-1h17155 model number KGL -40-751. So 1975 water heater.

On 2018-08-01 by (mod) - decoding the AO Smith data tag for manufacturing date

JT that's how I would read it, F = June, 01 = day.

On 2018-08-01 by JT

Looking for the manufacture date of: MF01-0047213-248

If I'm correct in this.... it was made in June of 2001 ... is that correct?

On 2018-07-13 by (mod) -

KC I would decode an AO Smith water heater serial number MB00-0070742 as follows:

Factory M

Month B = February

Year 00 = 2000

On 2018-07-13 1 by KC

My AO Smith water heater serial number is MB00-0070742. Would that indicate the heater was manufactured in 2000?

On 2018-07-07 by (mod) -

Yes that's how I'd interpret it, as K = Dec and 05 the year.

On 2018-07-07 by Paula

My hot water heater has serial number K05A143732. Am I correct that the date of manufacture is November of 2005?


...

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