How To Repair Stuck Thermal Coupling

Estimated reading time: 8 minutes, 12 seconds

Thermocouple with a Button

This situation caught me off baby-sit. I was presented with a thermocouple from an AO Smith, sealed combustion chamber water heater. The symptoms included that the h2o heater would go off for no reason.

Eventually he couldn't fifty-fifty get the pilot lit. With careful inspection, you could see information technology had a little button in line. I had never seen i before, simply this is what what I learned.

What is a thermocouple for anyhow?

Thermocouples are used in gas appliances that use a continuing pilot. That means that there is a small gas flame on all the time. Without the Thermocouple doing its thing, the pilot won't stay lit.

Other included safety devices

Flame sensors work similarly, and basically ensure that there is a flame before the gas is immune through the main gas valve to be turned into flame for oestrus. If information technology wasn't for a functional thermocouple, the gas valve would just allow the gas to flow into your home without beingness burned. This is when explosions happen, and entire buildings become blown to smithereens.

How thermocouples piece of work

A thermocouple is an impressive little safety device that senses the heat fabricated by a flame. Through a system of having dissimilar metals joined, thermocouples generates a millivolt charge of around 12 – but plenty to tell the gas valve that the pilot calorie-free is on. I think that the coolest part is that there are no moving parts.

OOPS!

Many appliances don't have thermocouples, similar gas stoves and barbecues. Considering of that, they need to exist watched closely and are very dangerous, especially around children and peculiarly in windy atmospheric condition.

The thermocouple is e'er loftier on the list of possible problems in gas appliances troubleshooting. Unless you are handy and understand how to test them and or change them out, I would recommend calling a professional. The trouble with this one in item was that information technology was intermittently shutting off the airplane pilot.

The tipping indicate

Information technology wasn't until that fateful morning when my friend's wife couldn't take a hot shower that hubby had to jump into action and fix information technology. He chosen on a Sunday to help make information technology better, and being the go to guy that I am, I accepted the challenge. It took lots of enquiry to notice what the aforementioned push was. It had a 190 stamped on it, and this is what we finally discovered.

The typical thermocouple costs about $7.00 The fancier i is $35.00. The little button is called a Thermal Cut Off, or TCO. Unfortunately, there is no place open up on a Sunday that carries the fancier ane. This reminds me of a "suspenders and chugalug fix" simply information technology is a "suspenders and two belts"… a bit of overkill in my stance. The burner assembly that includes the thermucouple is effectually $eighty

This is what A.O. Smith has to say virtually their fancy Thermocouple device.

Faulty Connection

COMBUSTION Sleeping accommodation 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 information technology volition open the
thermocouple circuit and shut off the main and pilot burner gas flow. The airplane pilot would have to exist relit
after the TCO has had sufficient time to absurd downward (sensor is below 120 degrees F).
The TCO performs two primary functions:
• In the event of combustible vapor ignition inside the combustion chamber, it senses the
corresponding increase in temperature and shuts off gas flow to the chief and pilot burners.
• If excessive temperatures inside the combustion sleeping room bespeak poor combustion due to
a clogged LDO screen or inadequate air for combustion, the TCO volition shut off gas flow to
the primary and pilot burners.

Flame arrestor from bottom clogged with grit

Ultimately I discovered ours had a broken weld at 1 side of the button that was most likely due to a manufacturing defect. I saw lots of complaints about this little push button, but no good solutions or explanation of what they were on the internet. There but wasn't any skilful advice about where to find them, or if they were essential.

How I fixed my problem

I replaced information technology with readily bachelor "universal type" from the hardware store . Information technology worked merely fine. There is a flimsy black plastic screen that I washed out.

On Mon, I went to the wholesale business firm and sure enough I institute them for $35.00 but they were out.

I but had to set up some other one where the only thing I could buy was a new burner assembly! $110 This one also had a broken weld at i terminate too. I am going to get a few of these trivial gems and keep them handy for the next big water heater problem.

The mysterious LDO & Flame arrestor

Turns out there is an LDO ways Lint, Grit & Oil Screen is a airheaded trivial plastic matter that yous can easily accept out and wash. Then there is the Flame arrestor (information technology is a hidden screen thing that is hard to get at). It is a 1/2″ thick sturdy ceramic air filter of sorts with thousands of very tiny holes that ordinarily gets clogged.

NEW SOLUTION INFORMATION 2-2017

AO smith redesigned the h2o heater so I guess we were heard loud and clear. The temp out push button nevertheless exists but it is hands accessible now and has a secret manual reset.

Signs of high temp

I was asked by a reader Joe Low, to participate in a solution for his 11 year sometime water heater that would temp out upon taking a shower. Once cooled off he would have to relight the pilot. I was going to get him a new burner assembly (Which he has already replaced one time) when I spoke with Lonny, the Manager of my Ferguson store. He assured me that I was making a fault, "Temp out is a sign of a problem!" it made sense to me, so we elected to just replace the water heater for prophylactic sake.

Ultimately, I used the removed water heater every bit a test subject. Upon disassembling it in the name of scientific discipline, I found this clogged flame arrestor (Image above) and some signs of excess heat in the burner box. (His utility room housed a furnace too but it was spotless.) You volition need a mirror to see the flame arrestor screen from below.

Temping out?

If your water heater is temping out, clean out this well subconscious part. Y'all can get to it from the bottom with a vacuum, (you'll need to adapt something to suck from the tiptop side of the air intake base of operations) or even better, use compressed air with a long flexible or bent extension. you tin can also to get to it from the elevation. It lives just nether the burner assembly (You will demand to remove the burner assembly to get admission). I suggest that you clean it from both directions as it is partially obstructed by metal from above. When I hitting this flame arrestor with compressed air the dust flew!

Naturally there is no mention of this flame arrestor in the possessor manuals. I say this sarcastically, considering it would be helpful if information technology was published for full general consumption, or avant-garde diagnostics.

Other things to check

The other matter that could be suffocating the flame is lack of combustion air.

Is your house is too well sealed ?
Is your utility room too well sealed?

This can exist easily checked with a piece of toilet tissue. (I will add a video soon)

Nosotros found one abode where the air filter comprehend door was missing, and so when the furnace kicked on, it was sucking the combustion gasses right out of the water heater elevation into the furnace intake (That is deadly) Ever look for signs of ringlet out on top of the gas water heater, and have a working CO monitor in the home.

The quick ready from readers:

This has been my almost pop weblog post of all times, the common theme of the comments is appreciative. The best solution I take discovered by accident is simply to re-solder the push button back on. I am not sure how long it volition last, merely I would charily recommend this fix to anyone. Any y'all do, remember messing with gas has gamble, practice not bypass safety features.

This house exploded in New Jersey as a result of a gas problem.

Mine just failed

I just had mine fail. I establish it simple to remove the three parts.

Gas line
Termocouple
Pilot gas line

Then I used my soldering iron to remove the push then filed off the dorsum to see the push button. Then I soldered the 2 brass parts. the directly one to the edge and the curved one to the center of the button. This was harder than information technology looked considering all the parts are small. All better now.

Bonus Circular Questions?

Who has a war story to tell most these things?
Who has some boosted helpful information they would like to share?

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