I would like to know what was the reason why the fire in a gas boiler
can be extinguished by itself. I have a relatively old boiler that
runs by natural gas to heat water for my baseboard heating units. A
couple days ago, somehow the fire in the boiler extinguished by itself
-- no fire, not even the pilot. The control switch was at the "ON"
position. But I didn't smell any gas. I can re-ignite the boiler
without any problem, and the problem has not returned; this is good.
But I would like to know why the fire in the boiler would be
extinguished in the first place.
I have the following specific questions:
- Would this happen when the natural gas supply was momentarily
running out of gas? But the fire in my relatively new water heater was
still burning while the fire in the boiler was extinguished. If the
natural gas supply was momentarily stopped, I would assume that the
fire in both the boiler and the water heater would be extinguished,
- Is the boiler smart enough to automatically switch off the gas
supply when it senses that the fire is extinguished? I am asking this
because the control switch was at the "ON" position but I didn't smell
- Will this happen when someone (like my 2-year-old child) toggles
the power switch of the boiler Off and On?
Thanks in advance for any info.
You bet! There should be a thermocouple (it looks like a closed metal
tube) sticking in the pilot flame. It senses the pilot and if it does not
sense a pilot flame or if the thermocouple fails it turns the gas off to
both the main burner and the pilot. They are cheap and easy to replace.
What you are observing is common when one is getting old. You can also try
cleaning it and or adjusting it to make sure it is in the hot part of the
flame. However they are cheap enough, most people just replace them.
It could under some circumstances, but don't blame the little guy yet.
Now, I understand what the "thermocouple" is for. I only knew that the
thermocouple is quite troublesome that I need to replace it almost
every year. I didn't really know what it is for. Now, I understand
what it is for and the reason why I didn't smell gas even when the
switch was at the "ON" position.
My little kid is still not off the hook yet. He is the kind of kid who
likes to toggle on/off any switch that he can have access, open all the
drawers in the kitchen, ...etc.
Yes, if your gas supply was interrupted, the boiler would shut off.
This is VERY unlikely and probably isn't your problem.
Yes, there is usually a thermocouple or sensor above the pilot flame
(in pilot ignited appliances like most older boilers and water
heaters). When that cools off, the gas supply is shut off. This is
why you need to hold the pilot button on many newer gas burners for a
few seconds after lighting to make sure the gas stays on while the
thermocouple heats up.
It's possible, does your 2yo spend much time near the boiler? Having a
2yo myself, it's something I would strongly discourage, with locked
doors if necessary.
If I had to guess, I'd guess you experienced some unusually high winds
recently, as did a large portion of the USA. Occasionally, a wind that
is unusually high or from a different direction than you are used to
will cause a backdraft down the chimney that can actually blow out a
pilot flame just like blowing out a birthday candle. When the pilot
goes out, the thermocouple cools down, and shuts off the gas supply
until someone comes along and relights it.
You may want to have your chimney and boiler inspected. In addition to
occasionally blowing out the pilot flame, this can also force
combustion gases (like carbon monoxide) into the house instead of going
up the chimney like they're supposed to. An infrequent occurance may
be just due to unusually windy conditions, but having your system
checked out by a professional would be the smart thing to do.
I'd have it looked at by some local boiler or hvac slack jaw. There are
plenty of reasons the boiler could have shut down....dont know exactly
how your boiler is set up but most gas equipment is equipped with
several "safeties" which will shut the thing completely down in the
event things are not running right.
Could be a thermocouple gone bad but it could also be other
things....we just dont have enough info on your particular piece of
equipment to know.
There are two power switches to the boiler. One of them is inside the
entrance of the side door. I don't know why the boiler needs a second
power switch near the side door. I have a feeling that it is an
emergency shutoff or something like that.
Yes, the boiler has a thermocouple, and it goes bad every year for some
unknown reason. I am trying to extend its life by shutting off the
pilot light when we are not in heating season; but I don't usually
remember doing this.
Seem like the thermocouple is what shut off the gas supply when the
flame is out. This explains the reason why I didn't smell any gas even
when I saw that the control switch was at the "ON" position.
OK, you are probably right. If that was the case, I would assume that
the fire in both the boiler and the water heater should have been
Thanks for the explanation of the role of thermocouple in keeping the
gas supply shut off when the flame was extinguished.
There are two power switches for the boiler. One is in the basement
right next to the boiler, another one is right inside the entrance of
the side door that is the primary thruway in and out of my house.
Therefore, this is quite easy for the kid to toggling Off and On the
power switch without being detected when I am bending down putting on
the shoes for the kids. I don't know why we have a second power switch
near the side door. May be it is an emergency shutoff or something.
Yes, you are right. The temperature in our area dropped significantly
in the evening when the flame of the boiler was extinguished; I am sure
there were high wind when there was cold front going through. And you
probably are on to something. But because we are in the heating
season, the boiler is on all the time (just a matter of high or low
flame). Even if the pilot light was blown off, the main flame should
not be blown off that easy right? And if the main flame was there, the
main flame should be able to re-ignite the pilot light (afterall, they
are right next to each other), right?
Anyway, I will go back home after work at around 5:00pm and check the
flame in the boiler to see if the main flame is ON or not. Normally,
the house should be quite warm at that time after a whole day sun shine
and a whole day of human activities inside the house. If the house is
warm enough for the main flame to go off, I should be able to observe
this at that time.
Yes, you are right. I believe we should have the boiler inspected and
cleaned every year. Thanks for reminding me about this.
you can buy cheap switch cover at electrical supply house so no one can
move a regular wall switch without a screwdriver. that might help with
a good friend has a 2 year old he is into everything
they say smart kids are worse perhaps that info helps a bit
I am hoping that he will out grow his bad habit. But a cover on the
switch that requires some force to open the cover is a good idea -- not
only good for preventing the little kid from fooling around the switch,
but also preventing the adults from mistaking it as the light switch.
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