# Thermocoupler



## Bill (Jun 17, 2008)

I was asked to go look at at a gas state water heater today. Thermo coupler was bad. My boss said to stop at Ferguson and get a new thermo coupler. So I did. I get there and the water heater thermo coupler has some kind of diode thing inline. He said to by pass it. I did, using a universal thermo coupler. The water heater worked fine. First time working on one. He said it was ok to bypass that little diode looking thing. My question is what is it for, and is it safe to bypass it?


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## OpenSights (Mar 23, 2015)

Edit....


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## OpenSights (Mar 23, 2015)

OpenSights said:


> Edit....


Read your post wrong at first, sorry... That worked?


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## Bill (Jun 17, 2008)

Works fine. Was just wondering what the pill looking part does. Can't seem to post a picture


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## Bill (Jun 17, 2008)

Here is what I am talking about


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## OpenSights (Mar 23, 2015)

Resistor or diode. I took mechanical drafting and tool design in high school, not electronics or plumbing/HVAC. I'm surprised it worked! I wouldn't want my liability on the the line by fixing a heater with the wrong part. I don't think it will explode or anything, but interesting temporary fix.


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## Debo22 (Feb 15, 2015)

It might be a fusible link designed to open if the burner flames are malfunctioning.


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## Toli (Nov 7, 2015)

Thermal switch. Set to open at 190 C. It's part of the fvir system.


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## Bill (Jun 17, 2008)

Ok, so, what do y'all think. Can it be bypassed using a universal thermocoupler?


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## OpenSights (Mar 23, 2015)

IMHO, if it works for the weekend or till you can get back, cool. I wouldn't leave it there and let the HO know how you temporarily give.them hw, and let them sign a waver.


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## OpenSights (Mar 23, 2015)

Two reasons for failure: product failure or a disaster prevention.


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## Toli (Nov 7, 2015)

Bill said:


> Ok, so, what do y'all think. Can it be bypassed using a universal thermocoupler?




The thermocouple will function fine without it. But, you eliminated a factory safety. I guess you need to ask yourself if you're ok with that. 

I'm not passing judgement here. Sometimes you gotta do what you gotta do.


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## Bill (Jun 17, 2008)

What I am saying is i replaced the thermo coupler with a new one, its just that the new one does not have that thing inline.


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## plumberkc (Jun 23, 2011)

Sorry Bill but your boss is a hack, that's a total handyman move here and could lead to somebody dying. The reason ALL water heaters after 2003 are required to have that are in case the flue or chimney is obstructed. If the chimney collapses it will vent into the house and kill somebody. Or could possible catch on fire, definitely not worth the risk. Especially when the right part is so easy to stock. I mean why even show up to a no hot water call without a 100 series PA? 


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## Sipp (Jul 14, 2016)

You modified an appliance from how it was designed and certified. In the event something bad happens, the manufacturer will take ZERO responsibility and throw you and your boss to the wolves. 

The best way to think of this issue is, how would you feel if the customer was your mom or grandparent and a contractor did this?


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## OpenSights (Mar 23, 2015)

Hard on you, overnight, but it needs to be replaced with the right part. I'm all for temp fixes with a return call, but not permanent.

What's our code? Something about Heath and wellfare?


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## indyjim (Apr 29, 2017)

My code is don't do anything at anyone's home you wouldn't do at your own home. 


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## Bill (Jun 17, 2008)

plumberkc said:


> Sorry Bill but your boss is a hack, that's a total handyman move here and could lead to somebody dying. The reason ALL water heaters after 2003 are required to have that are in case the flue or chimney is obstructed. If the chimney collapses it will vent into the house and kill somebody. Or could possible catch on fire, definitely not worth the risk. Especially when the right part is so easy to stock. I mean why even show up to a no hot water call without a 100 series PA?
> 
> 
> Sent from my iPhone using Tapatalk


There you go. I did not say I was leaving it like that. Matter of fact the new one came in this morning. Picked it up, swaped it out. All I wanted was for someone to explain what that particular part is for. I know what and how the thermo coupler works, I just wanted to know what the additional part was. So, if I understand you right, if the flue clogs up, the hot fumes can not escape, feed back into water heater, causing that diode looking part to shut down the water heater, correct?


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## indyjim (Apr 29, 2017)

Exactly. 


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## OpenSights (Mar 23, 2015)

indyjim said:


> My code is don't do anything at anyone's home you wouldn't do at your own home.
> 
> 
> Sent from my iPhone using Tapatalk


 If I had the same code, you'd loose your mind over the plumbing in my house! I've had to do repairs, not exactly right, but they work.

When I get home I have time for billing, not plumbing.


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## Bill (Jun 17, 2008)

That's all I wanted. An answer. Just like a water saver in shower heads. Yes, they are installed by the manufacturer. But I remove them. Just like y'all. Does it hurt? No. Is it legal, no. But we do it. If I want to know how to get to Florida from new jersey, then I expect people to say 95 south. But when you ask a question on here about how do I get to Florida from New Jersey it seems people here want to say go through Pennsylvania, then Ohio, West Va, Tennessee, North Carolina, South Carolina, then Florida. And y'all wonder why nobody wants to join this website. It's because y'all think just because everyone is a LICENSED plumber they know everything about everything. I am a VA licensed master plumber and a VA licensed Class B building contractor. But I will tell you I do not know everything about everything. Yes I do have to go to continuing education classes to keep my master license going. I asked a simple question. I thought I wood get a simple answer but I did not. Instead I get ridiculed. And y'all wonder why people don't want to associate themselves with this website. Y'all think y'all so smart. How do you calculate the diagonal measurement of a house if you are given the width and depth? How many degrees is there for every inch of per foot of fall per inch on a rafters? How many square feet of ventilation is needed on a house? The point is I not only have to keep up with plumbing codes but I also keep up with building codes. I do not like fooling with gas. It scares the crap out of me. Everyone here thinks that everyone should know everything. This is why I am stepping down as a moderate.


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## indyjim (Apr 29, 2017)

Cool your jets, it's just a plumbing board. We're all *******s it's in our nature. 
As for your questions, I'd have to dig my shop mathematics book out. 
When in doubt, vent all the soffit. 


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## Buddy (Oct 25, 2009)

Hello Bill It seems that the part would perform the same function as a "Spill Switch" on a boiler which is designed is to keep Flue Gasses or Flames from Spilling out of the boiler and into the room. Now I learned what that Part is for from reading about your Inquiry. Thank You


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## PLUMBER_BILL (Oct 23, 2009)

Buddy said:


> Hello Bill It seems that the part would perform the same function as a "Spill Switch" on a boiler which is designed is to keep Flue Gasses or Flames from Spilling out of the boiler and into the room. Now I learned what that Part is for from reading about your Inquiry. Thank You


*Wish I would have installed a spill switch. Damn near killed a family quite a few years back. We had installed a gas boiler -- any-way the boiler came with a bi-metal flue damper. We installed as per factory spec, job worked good, passed inspection and now we fast foreward about a year and 1/2 . Got a phone call late Friday at this job for a kitchen faucet dripping, said I would not get there today anymore but I would come in Saturday morning early we had set a time for 7:30 A.M. That night there was a terrible storm, the lot this house sits on slopes toward the back with a concrete walkway along the side. The rain water cascading down that channel built up around the outside chimney and found a hole through the brick morter and washed all the debris in the chimney which all landed on the top of the bi-metal flue damper the weight held the damper closed. The house was full of carbon monoxide. At 7:30 in the morning I still don't know how but the noise I was making knocking on door ringing the bell woke up one of the kids, we he opened the door I could smell the products of combustion ran in and started opening up. Every-body got out , Thank God ... A spill switch would have ended the problem and alerted the occupants. This is not a boiler problem, It was strictly the fault of the monsoon rain storm and the way the chimney was built. 
*


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## Bill (Jun 17, 2008)

Buddy said:


> Hello Bill It seems that the part would perform the same function as a "Spill Switch" on a boiler which is designed is to keep Flue Gasses or Flames from Spilling out of the boiler and into the room. Now I learned what that Part is for from reading about your Inquiry. Thank You


Thanks! That's all I wanted to know. We do not know everything. Anyone who says they know everything is a lying. To prove a point, we all know you must maintain a 2 inch air gap when potable water can come in contact with waste water. Well, why is it then I see so many licensed plumbers install tub spouts flush with the lip of a tub?

But thanks, now I know exactly what it is for and what it does.


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## jc-htownplumber (Feb 29, 2012)

Next time you can go sears they sell them. Yes I have done it before with no problem. My house came with a whirlpool heater. The first time the heater went out I didn't have the correct icon valve or thermopile, what I did because my newborn at the time and wife needed hot water on a cold winter night. I found an old mechanical gas valve and burner assembly, I used that until new parts came in


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## Tommy plumber (Feb 19, 2010)

So the thermal switch has been on all gas W/H's since 2003 or just a specific brand?


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## jc-htownplumber (Feb 29, 2012)

The "pill" I think it's on the state water heaters and sears water heaters 


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## Toli (Nov 7, 2015)

Tommy plumber said:


> So the thermal switch has been on all gas W/H's since 2003 or just a specific brand?




The one in the pic was on the AO smith family. It was their first series of fvir heater. 

Everyone has one of some sort. AO smith has since moved the switch to the burner cover like everyone else. The switch has one function- to open the tc circuit if the temperature gets above the rating of the thermal switch. Flue problems can cause that along with a handful of other things.


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## Tommy plumber (Feb 19, 2010)

Toli said:


> The one in the pic was on the AO smith family. It was their first series of fvir heater.
> 
> Everyone has one of some sort. AO smith has since moved the switch to the burner cover like everyone else. The switch has one function- to open the tc circuit if the temperature gets above the rating of the thermal switch. Flue problems can cause that along with a handful of other things.














Have you seen those sensors ever fail for reasons other than what they were intended for? In other words, instead of the chimney becoming blocked and tripping the safety switch, will the switch fail for some other reason, like being tampered with or shorting out somehow?


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## OpenSights (Mar 23, 2015)

I've seen them fail for no apparent reason before. I just chalk it up to our disposable society. 

Not really on topic, but since tampering was brought up; a few weeks ago we got a call for no hot water at a rental, codes were control valve and something else, but LL didn't know because she didn't look at it. We get there and the burner assembly is ripped out, new thermo package from HD on the floor and the pilot light tube cut into pieces. Well the maintenance guy tried to replace it. Story is he worked on it for four hours and every time he went to light it there was a very strong gas smell. According to the tenet she packed up her dogs to go visit a friend.

We looked up a gas control valve and a complete burner assembly, and with a mark up came to about $50 less than a new heater. A couple days later we installed a new heater.


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## Toli (Nov 7, 2015)

Tommy plumber said:


> Have you seen those sensors ever fail for reasons other than what they were intended for? In other words, instead of the chimney becoming blocked and tripping the safety switch, will the switch fail for some other reason, like being tampered with or shorting out somehow?




It's been my experience that usually they fail for a reason. Typically it's a combustion air quantity problem. Other times it's a flue. Sometimes it's because the burner lit off something other than Nat Gas. And sometimes they just stop working properly.

I think, but don't know, the switches can get weaker over time or weaker once they have opened. Meaning instead of opening at 190C they may open at a cooler temp.


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## GAN (Jul 10, 2012)

Bill said:


> That's all I wanted. An answer. Just like a water saver in shower heads. Yes, they are installed by the manufacturer. But I remove them. Just like y'all. Does it hurt? No. Is it legal, no. But we do it. If I want to know how to get to Florida from new jersey, then I expect people to say 95 south. But when you ask a question on here about how do I get to Florida from New Jersey it seems people here want to say go through Pennsylvania, then Ohio, West Va, Tennessee, North Carolina, South Carolina, then Florida. And y'all wonder why nobody wants to join this website. It's because y'all think just because everyone is a LICENSED plumber they know everything about everything. I am a VA licensed master plumber and a VA licensed Class B building contractor. But I will tell you I do not know everything about everything. Yes I do have to go to continuing education classes to keep my master license going. I asked a simple question. I thought I wood get a simple answer but I did not. Instead I get ridiculed. And y'all wonder why people don't want to associate themselves with this website. Y'all think y'all so smart. How do you calculate the diagonal measurement of a house if you are given the width and depth? How many degrees is there for every inch of per foot of fall per inch on a rafters? How many square feet of ventilation is needed on a house? The point is I not only have to keep up with plumbing codes but I also keep up with building codes. I do not like fooling with gas. It scares the crap out of me. Everyone here thinks that everyone should know everything. This is why I am stepping down as a moderate.


What a long one. Looking back right or wrong, you did at first just ask if it can be by passed, it was not until a later post did you mention you had picked up a new one to install.

I completely agree and I often leave my perfect pin at home myself. I can't read minds either so just going by the first post it signaled a possible danger is why I believe you got the flack (not so much you but your Master I assume). I have a different opinion on that. Your other professional constituents thought enough to give a warning to help protect you, not so much as to jump you. Just my opinion. We are trying (in most cases) to help & protect others. :thumbsup:


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## Bill (Jun 17, 2008)

I did text my boss. Told him I AM THE MASTER PLUMBER, and after some research found out it's a failsafe. He wants me to obide by his codes, I told him he must obide by mine. Told him since I know what it is, what it's for, what it does I refuse to bypass it any more.


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## indyjim (Apr 29, 2017)

Is this still going? 
Good lord.... we have all busted the sight glass out on those crappy first gen "safe" water heaters, bypassed flame roll out switches, etc.. Once I bypassed a flow switch on a boiler system to get a hotel through the weekend. 
You went back and fixed it correctly. 
+1 to you, sir. 


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## Debo22 (Feb 15, 2015)

indyjim said:


> Is this still going?
> Good lord.... we have all busted the sight glass out on those crappy first gen "safe" water heaters, bypassed flame roll out switches, etc.. Once I bypassed a flow switch on a boiler system to get a hotel through the weekend.
> You went back and fixed it correctly.
> +1 to you, sir.
> ...


And we all install a new gasket every time we open the water heater burner chamber just like it says to do :whistling2:


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## GAN (Jul 10, 2012)

It all depends on how much risk your willing to take, gambling over the odds. Like getting in a ditch without proper shoring, your fine until it collapses or OSHA comes by.


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## sparky (Jan 8, 2014)

Tommy plumber said:


> Have you seen those sensors ever fail for reasons other than what they were intended for? In other words, instead of the chimney becoming blocked and tripping the safety switch, will the switch fail for some other reason, like being tampered with or shorting out somehow?[J/QUOTE]
> 
> If that switch shuts down for whatever reason,do you have to replace it every time or does it reset itself???i never seen one of these dodads either


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## sparky (Jan 8, 2014)

OpenSights said:


> I've seen them fail for no apparent reason before. I just chalk it up to our disposable society.
> 
> Not really on topic, but since tampering was brought up; a few weeks ago we got a call for no hot water at a rental, codes were control valve and something else, but LL didn't know because she didn't look at it. We get there and the burner assembly is ripped out, new thermo package from HD on the floor and the pilot light tube cut into pieces. Well the maintenance guy tried to replace it. Story is he worked on it for four hours and every time he went to light it there was a very strong gas smell. According to the tenet she packed up her dogs to go visit a friend.
> 
> We looked up a gas control valve and a complete burner assembly, and with a mark up came to about $50 less than a new heater. A couple days later we installed a new heater.


Yep,you are correct,once you disassemble all that control valve and wires I don't think it ever works right again,I mean it will work,but seems like never as good as original,always something going on with it


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## GAN (Jul 10, 2012)

Look for faults first, blockages, wiring etc. then retry once. As Toli listed above. If the fault continues replace and verify operation.

If your not familiar with these here is a basic guide for troubleshooting.

http://waterheatertimer.org/How-to-repair-Rheem-FVIR.html


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## OpenSights (Mar 23, 2015)

The maintenance guy pretty much destroyed it. From the codes he says he saw it was the control valve and thermo. Why he decided to cut the gas line, no clue. This is more of a message to the LL , don't have your dumb azz maintenance guy work on your plumbing!


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## wyrickmech (Mar 16, 2013)

Kinda like a roll out switch.


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## panther (Oct 27, 2010)

That little piece is designed to break in the event of an internal fire/overheating. The problem with just swapping it out with a regular thermocouple and not the entire pilot assembly is not just the diode, but the rubber bushing that comes with it. I'm certain that you had to cut the rubber bushing to accommodate the new thermocouple, which could draw in too much oxygen and cause a fire. I had it happen once a long time ago. It was just until the part came in repair. In one day it burnt the thermocouple to a crisp. Fergies carries that entire assembly, which is the same for State and AO.


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## jnohs (Jan 27, 2012)

Bill said:


> I did text my boss. Told him I AM THE MASTER PLUMBER, and after some research found out it's a failsafe. He wants me to abide by his codes, I told him he must abide by mine. Told him since I know what it is, what it's for, what it does I refuse to bypass it any more.


WORD!!!! thats how you become the master!!!!!!!

Also with this spill switch. It is now absolutely a mandatory upgrade of the flue piping to a 4 inch pipe when installing a new water heater... For more reasons then code.... If a 3inch flue is installed the water heater does not draft properly and sooner or later it will get hot underneath and actuate the spill switch..Also this sort of issue will usually present it self on the coldest night 6 months from when you put it in right during the busy season..... Avoiding incorrect installation, and callbacks a 4inch flue pipe is 100% not an option... It is mandatory.


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## jnohs (Jan 27, 2012)

It is like the movie "The last dragon"----->"Who is the Master....? I am The Master!!!!!!"


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## jnohs (Jan 27, 2012)

Hi yah!!!!!!!!!!!!!!!!!!!!


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