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Gas appliances, how do they work?

S

spidey07

No Lifer
Seems like a simply question but I've always wondered.

"If the pilot light goes out, why am I not killed by gas as it is slowly released?"

"how can it not just run on the burners and flood the room with gas?"

I just don't get it or understand how it could work. Any furnace experts care to explain to a fellow engineer?
 
the pilot keeps a valve open due to the heat. if the pilot goes out, the heat sensor thingy gets cold and the valve shuts

that is why you have to hold the thing in for ~1 minute when lighting the pilot (when it is cold), you have to keep the valve open manually while it heats up (so that it will stay open)
 
Originally posted by: spidey07
Seems like a simply question but I've always wondered.

"If the pilot light goes out, why am I not killed by gas as it is slowly released?"

"how can it not just run on the burners and flood the room with gas?"


I just don't get it or understand how it could work. Any furnace experts care to explain to a fellow engineer?
Click to expand...

1) Not sure, but I'll bet it's somthing simple - like a valve.
2) It's called a valve.
 
Text - Enjoy

The thermocouple is located near the pilot light. It is designed as a safety feature that automatically turns off the gas supply should the pilot go out. It works by generating a small amount of electricity when heated, keeping the gas valve open. The gas control valve is essentially a "dead man switch"... if the electricity stops flowing, the switch opens and the valve closes.
Click to expand...
 
Originally posted by: spidey07
Originally posted by: Pliablemoose
http://hearth.com/what/gas/howgasworks.html

thermocouples biatch😉
Click to expand...

well how do said termocouples work?

teehee.
🙂
Click to expand...


A thermocouple is a device made of two different metals which creates a small electrical charge when heated at one end by the gas pilot. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the main burners. Since the thermocouple must be heated before the burner will start, gas appliances often have a startup mode, during which a knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough electricity for the valve to operate correctly. At this time, the startup knob can be released and the valve turned to an "on" position for appliance operation.
Click to expand...
 
Originally posted by: lobadobadingdong
none of my gas appliances have a pilot light, electonic ignition.
Click to expand...

well that goes back to my point.

To make heat = release gas to open flame

What's to prevent the appliance from throwing gas when there is no flame? what happens when there is no power to the valves/controls?
 
Originally posted by: spidey07
Originally posted by: lobadobadingdong
none of my gas appliances have a pilot light, electonic ignition.
Click to expand...

well that goes back to my point.

To make heat = release gas to open flame

What's to prevent the appliance from throwing gas when there is no flame? what happens when there is no power to the valves/controls?
Click to expand...


That's it, turn in your Craftsman screwdrivers😉
 
Originally posted by: Pliablemoose
Originally posted by: spidey07
Originally posted by: Pliablemoose
http://hearth.com/what/gas/howgasworks.html

thermocouples biatch😉
Click to expand...

well how do said termocouples work?

teehee.
🙂
Click to expand...


A thermocouple is a device made of two different metals which creates a small electrical charge when heated at one end by the gas pilot. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the main burners. Since the thermocouple must be heated before the burner will start, gas appliances often have a startup mode, during which a knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough electricity for the valve to operate correctly. At this time, the startup knob can be released and the valve turned to an "on" position for appliance operation.
Click to expand...
Click to expand...

well that I can understand (barely, what kind of metal are we talking and how small is the potential?)

But that system still has a electrical valve control right? There has to be some kind of electrical control system doing the opening of valves? or maybe not?

I'm confused.

😕
 
Originally posted by: FoBoT
i think he is pulling our chain
Click to expand...

not really, I'm pretty handy and have a degree in EE/CS and am intimately familiar with control systems. I really am haveing trouble understanding exactly how this works.
 
Originally posted by: spidey07
Originally posted by: Pliablemoose
Originally posted by: spidey07
Originally posted by: Pliablemoose
http://hearth.com/what/gas/howgasworks.html

thermocouples biatch😉
Click to expand...

well how do said termocouples work?

teehee.
🙂
Click to expand...


A thermocouple is a device made of two different metals which creates a small electrical charge when heated at one end by the gas pilot. This small charge causes an electromagnet inside the gas valve to open and allow gas to flow to the main burners. Since the thermocouple must be heated before the burner will start, gas appliances often have a startup mode, during which a knob must be depressed and held for 30 seconds or so after lighting the pilot. At the end of the 30 seconds, the pilot should be generating enough electricity for the valve to operate correctly. At this time, the startup knob can be released and the valve turned to an "on" position for appliance operation.
Click to expand...
Click to expand...

well that I can understand (barely, what kind of metal are we talking and how small is the potential?)

But that system still has a electrical valve control right? There has to be some kind of electrical control system doing the opening of valves? or maybe not?

I'm confused.

😕
Click to expand...

The valves are made such that in the event of a power faliure, bad wiring, etc- they just close.
 
picture
did you look at the pictures?
picture
thermocouple voltage level is determined by the types of metal used, usually millivolts (IIRC)
that feeds a control circuit to tell the solenoid to keep the valve open so the gas flows while the pilot is lit
 
WTF is so complicated about a pilot-less stove?

the gas is closed. you turn the knob, it lets gas out snd strikes simutaneously. the knob is the valve.
 
Originally posted by: FoBoT
picture
did you look at the pictures?
picture
thermocouple voltage level is determined by the types of metal used, usually millivolts (IIRC)
that feeds a control circuit to tell the solenoid to keep the valve open so the gas flows while the pilot is lit
Click to expand...

bingo - now we're talking. An electrical control system that activates a solenoid. no power = no solenoid action.

that makes sense.

But deeper? how does the metal generate the potential difference? Expansion?
 
Originally posted by: Colt45
WTF is so complicated about a pilot-less stove?

the gas is closed. you turn the knob, it lets gas out snd strikes simutaneously. the knob is the valve.
Click to expand...

well that is pretty straight forward:

1) turn knob
2) piezo starts clicking
3) flame
 
The newer gas furnaces use a flame sensor that the flame makes a circuit from the burner to the flame sensor. Proving to the control board or module that flame is present and to continue normal operation. If the ignition system didnt achieve ignition then there would be no circuit to the flame sensor and the burner control or module would shut down the valve. It will dump raw gas for a few seconds only. The control could retry after a certian amount of time (Soft lockout) or lock out hard in which case power to the control would have to be interupped to reset control
 
To be brief, old gas stoves didn't. They had a pilot light for each pair of burners (typically) with ducting to direct gas to the pilot light when the burner valves were opened by a purely mechanical setup.

The pilot light was a simple needle valve and if it went out, then it went out and gas came out of the valve. The valve didn't pass that much gas though and it dispersed just fine in a normal home. We had a really old gas cooktop that would have the pilot go out all the time. Never caused a proble. There wasn't enough gas to cause an explosive concentration.

ZV
 
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