Knob on water heater thermostat

[Mark P]

Can someone please tell me what the name and purpose of the tan (not black) round knob on top of the the thermostat.

Thank you

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[Chad Fabry]

As a rule one must hold that knob down while lighting the pilot until the thermocouple gets hot enough to generate 2-6 millivolts and allows the gas valve to open.

Alternatively, it may be a Lego some kid put there.

[Neal Lewis]

I would also go with the Lego theory, since the diameter of the knob is smaller and can now be pushed down without the gas control in the pilot position.

[Mark P]

Thanks,

Well the reason I'm asking is that I inspected this WH, detected a small gas leak from where the pilot light tub connects to the control box and wrote it up. 3 days later was contacted by the selling ageant saying the pilot had gone out, since I live close by and the sellers don't speak much english would I stop by take a look and expalin whatever needed to be explained to them. (like hire a plumber as the report stated) anyway when I stoped back by I found this knob was broken completly off, I told them there was nothing I could do and to call a plumber, they pretended like they new nothing about the knob, well they paid over $400 for a new theromcouple and control box for this 10 year old heater and they want me to pay for it. I'm having to write a letter explaning the facts and providing pictures, etc and I wanted to know what the stupid knob was called.

[Bill Kibbel]

If it's the button that you depress during, and shortly after, lighting the pilot, it's simply called the reset. It holds open the gas interrupter temporarily until the thermocouple tells the electromagnet to keep it open.

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I fear you may have been framed. Not to mention a gas control valve is about $65.00.

[Bain]

I agree, about the framed part. I had some chick go off last week because I poked my finger through the water-damaged drywall beside her tub. I listened, politely, then offered to send her a $20 check to pay someone to plug the dime-size hole with some joint compound. I did, of course, want to say something entirely different, but WTF.

[paul burrell]

The gray flex gas line is a recalled item approximately 4 years past +-. I have a flyer on the recall that I received at ASHI meeting. The gray flex tends to break and leak at fittings. There is still a lot of it out there and I call it to be replaced with stainless steel flex or yellow up graded flex. I do not see gray flex on newer homes anymore.

Paul B.

[Mark P]

Okay, thanks, I guess I'll refer to it as the "reset button"

[Jim Katen]

Originally posted by paul burrell

The gray flex gas line is a recalled item approximately 4 years past +-. I have a flyer on the recall that I received at ASHI meeting. The gray flex tends to break and leak at fittings. There is still a lot of it out there and I call it to be replaced with stainless steel flex or yellow up graded flex. I do not see gray flex on newer homes anymore.

Paul B.

If you've still got that flyer or know of a link, please post it. I'm familiar with the faulty brass flex connectors, but I've never heard of a problem with the grey ones.

I see a ton of them so if they're defective, I need to know about it.

- Jim Katen

[Bain]

I saw a grey gas-line today, and remembered this post. Without anything concrete, I didn't mention the line as a defect.

[Bill Kibbel]

Bad connector, uncoated brass:

OK connectors:

I'll bet the flyer that was passed out had a black & white line drawing and many HIs assumed it was the gray connectors.

I really need to clean out my hard drive.

[Bain]

I like the hard drive just the way it is, Bill.

T'anks.

[Chad Fabry]

Sadly, my hard drive is like my brain. I have a lot in there but I can't access it efficiently.

[homnspector]

Mark, that cap covers a regulator adjustment that varies the gas flow and output of the burner flame.

This is a GE water heater manufactured by Rheem. I don't know who manufactures the control. Apparently Fort Knox if it costs $400.

On these controls, the black knob is pushed down to light the pilot, not the tan cover. If it is broken or missing it doesn't make any difference, replace it with Chad's Lego. Here are some Pics

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[Chad Fabry]

Thanks for that Fritz.

[homnspector]

Chad, While we are on this subject, maybe you know the answer to this, it has been bugging me for years and I have tried to find the answer from alot of sources.

"the thermocouple gets hot enough to generate 2-6 millivolts and allows the gas valve to open"

How exactly does this miniscule amount of voltage open a valve? I am sure it isn't enough to operate any kind of solenoid I have seen. Every gas appliance uses thermocouples and they are pretty bullet proof. I understand the principle that heating dissimilar metals produces current but not the physical process that opens or closes the valve. I have disected control boxes to no avail.

[Chad Fabry]

I'm not sure I can give you a definitive explanation from the one or two valves I've opened but I'll start the discussion and maybe others will add.

It always bothered me that 3 millivolts was enough power to open 150,000 btu gas valve because of 1)the mass that to be moved operating the valve and 2) how did it overcome the .5psi of gas pressure.

It's been years since I looked but the millivolt signal operates a very small valve..reed type assmbly with almost no mass and blocking a very small hole.

When the hole is blocked, a spring pressure on a diaphragm holds the valve closed and there is the pressure of natural gas on each side of the diaphragm. When the hole has been opened (calling for gas)the gas bleeds off (as I recall to the pilot)leaving atmospheric pressure on one side of the diaphragm and the gas pressure on the other side. The pressure of the natural gas on the diaphragm overcomes the spring and atmospheric pressure (.5 lbs on 2 or 3 square inches of diaphragm adds up) and moves the valve assembly to allow the burn. As the valve assembly moves, it closes off the gas supply to the control side of the diaphragm.

When the system stops calling for gas, the little valve closes, gas fills the control side of the diaphragm and with the aid of the spring preload, moves the valve back to the closed position.

I offer this info admitting that it's what I remember from the dissection of a valve maybe ten years ago. There may certainly be some skipped nuance of the operation.

[Les]

The voltage does not open the valve. It allows the valve to be opened, typically mechanically. The thermo-couple is a solonoid.

[Chad Fabry]

Hi Les,

The thermo couple isn't a solenoid, but I understand what you mean.

The solenoid is actuated by the voltage generated by the thermocouple. The solenoid actuates the small valve that relieves pressure on the diaphragm.

To be clear; I'm referring only to millivolt water heaters and furnaces which do not need external electricity to operate.

[Les]

Chad, you are right. I meant the assy.

[homnspector]

So, sounds similar to some styles of toilet fill valves. By opening a tiny pinhole, the actual valve is forced open by the gas pressure.

[Les]

Ya, kinda like the difference between beans and broccoli!