In my experience, I have seen three different kinds of pilot lights:
[ol]
[li]On a kitchen stove (whether consumer or institutional), one simply puts a flame to the pilot light next to each burner, and that’s it, very simple and easy. (This is becoming rarer nowadays, being replaced with electronic ignition to conserve gas, but that’s not what this thread is about.)[/li]
[li]My clothes dryer runs on gas. Well, the spinning is electric, but if the gas is not hooked up there won’t be any heat. I have no idea how the gas burner fires on. No one ever lit a pilot light when we installed it, but it works fine. I presume there’s some sort of electric ignition which needs no help from me.[/li]
[li]Ovens (consumer and institutional) and my home heater are a whole 'nother breed. To light these, I need to get on the floor with either a long match or butane lighter, insert it into the oven where the pilot light is located, and then press and hold a button for anywheres between 30 seconds and two minutes, until I can release this button with no fear that the light will go out. Often I have to do this several times until the flame will stay on by itself.[/li][/ol]
This post is about the third of these. Why are they so difficult to light? What makes the flame go out when I let go of the button? Why can’t they be designed like the other kinds?
I wouldn’t mind so much bending down and reaching in and pressing the button and lighting the light, if I didn’t have to hold the button so long like an idiot. The gas obviously is flowing; what happens when I let go? I wouldn’t even mind holding the button for a mere 5 seconds or so, if that would be enough to keep it on.
[rant] Take this morning for example: The instructions on this particular oven say to keep the match on the light for 30 seconds. But experience has shown me that this is not long enough. (This is an institutional oven less than a year old.) So I’m lying on the floor, with one hand holding the match, and the other hand pressing the button, and my neck craned to see the second hand on my watch. After sixty seconds I let go of the button, and the flame goes right out. My butane lighter is empty, so I have to get off the floor and relight the long match from the stove, get back on the floor, and do the same thing again, but for two minutes this time, which finally worked. Aaargh!. [/rant]
Systems like these use something called a thermocouple.
A thermocouple looks like a stiff wire almost. It is a probe made up of a couple different metals, One end of the thermocouple is connected to the gas valve, where it receives an electrical signal.
The other end sits in the flame. When you apply heat/flame to the thermocouple for a sufficient time it creates voltage—electricity. It’s low voltage, less than 1 volt.
Still, that <1 volt “tells” the gas valve that a pilot light is present. (because, of course, if there was no pilot light there would be no heat, and no voltage)
This is important because if there was no pilot light there would be no ignition. If there was no ignition raw unburned gas would be flowing full tilt into the home; a Very Bad Thing.
But the thermocouple needs a little help to get warmed up-----it needs to be on long enough to generate enough heat to generate the <1 volt that the gas valve requires to cooperate.
By manually holding up the gas valve (the pilot side of the gas valve) you’re allowing the thermocouple to heat up. Once it is hot enough to hold the the “pilot solenoid” open on it’s own (without your help) you can let go of the button.
It’s a necessary safety feature.
And it often takes a lot more than 30 seconds. I don’t know why they say that.
From what I can gather from your “Rant”, you are holding the match or lighter the full time? It takes a split second to light the pilot while you are pushing the knob in to by-pass the electric safety valve, and then by just holding the bypass open for 30 sec >< the thermocouple should hold the valve open.
When i think about why it would take more that 30 sec. >< I would wonder if the pilot flame is adjusted correctly. I use a propane heater very often when I am Ice fishing and the pilot will stay on after about 15 sec. of holding it in bypass.
Or, maybe you are blocking or interfering with the flame if you are keeping the lighter in the way after you get pilot ignition???
Your explanation is extremely clear. Thank you so very much. So much so, in fact, that I’d almost consider the thread closed, except for a few follow-up questions:
I see why the newer stoves don’t need the thermocouple, since there is no pilot light, so if the stove is off there’s no gas leaking. But why didn’t they use this great safety feature in the old ones? I recall hearing about many home fires and asphyxiations were traced to the gas from a pilot that went out, so why did we have this feature only in the oven, and not in the stove?
Also: How does my clothes dryer work? It seems to be the best procedure of all. No manual pilot light, and I sure hope it’s not leaking gas.
Why no thermocouple on the burners? Probably cost.
I doubt that anyone ever died of asphyxiation from a pilot light being out. Houses (especially back in the day) just aren’t that air tight, and pilot lights don’t use a lot of gas.
A stove top pilot light is easy to see if it is working (lean over and look in the hole) and if you don’t do that, it is obvious that it isn’t when the burner does not light. Relighting is also easy.
None of that is true for an oven or a furnace.
Your clothes drier and your stove top work exactly the same way, when the gas is turned on, a piezo electric igniter creates a spark which ignites the gas.
What I don’t understand is why your oven does not also have one, it is my understanding that igniters have been required (at least in the US) for many, many years now as a gas saving feature. While one pilot light does not use much gas 80 or a 100 million of them do.
There’s a glow igniter. It heats up, once the detector feels the heat, solenoids open up, the gas flows and whoosh. Since a dryer needs electricity for the motor anyway, this works better than a constantly lit pilot.
Note that the “hold for 30 seconds” systems work best for systems that don’t otherwise need electricity and/or have a thermostat to maintain a set temperature. (Ovens, water heaters, pool heaters, etc.)
[Don’t have experience with piezo igniters myself.]
I’m an HVAC guy, although stoves operate under the same principles as furnaces. (with some differences as to safeties etc)
I just had a customer ask us to install a stove (including running a gas line) that was brand new.
The stove top burners had no thermocouple at all. The pilot tubes therefore flow gas uninterupted with no means of “proving” a flame, which is exactly what a thermocouple does**: prove a pilot flame exists.**
What that means is that if the pilot light blew out raw gas would flow uninterupted. This was brand new stove. Clearly that isn’t enough gas to be dangerous, but it is raw unburned gas flowing uninterupted.
The oven was different. It had a thermocouple and raw gas would not have flowed into the oven without a pilot flame. (which, of course, is what the thermocouple “proves” for you)
Clearly this is OK. I don’t like it one bit, however. If your pilot light goes out it’s one thing to have the pilot gas flowing. It’s another thing entirely to have your 5 year old turn the burners up all the way and have the **full flow of unburned gas of the stove top burners ** while you’re napping in front of the TV.
This was a rental property and so was the budget stove. But with all the new technology that’s come out in the last 20 years I can’t understand why stoves like this are still being allowed to be sold.
But when you refer to to old technology, was it in fact old?
Where were the burner control knob’s located?
The gas range I have in my cabin doesn’t even have pilot’s, the burners must be lit and the knobs are right on the front of the stove
Our Wood range gets used much more than the gas range;)
Is this really something to be worried about, though? How often does a pilot light go out on its own?
I say this while admitting that I’m completely ignorant about modern day stoves.
I have an old Caloric from probably about the 40’s or 50’s. No ignition. None of this fancy button pressing that you all are talking about…what is that all about, anyway?
I’ve had the stove about 15 years. The pilot lights (2 pilot lights for 8 burners) have gone out maybe 2 or 3 times during this time, most likely because I’ve left the window the stove sits right next to, wide open.
I could see my ovens being a problem. Once turned on the gas to one of the ovens but forgot to poke a match into the little pilot hole (that won’t happen ever again).
