I learned something new tonight
I learned something new tonight
(OP)
Although I used to service and set-up gas-fired industrial equipment in excess of 1,000,000 BTUs I must admit that I was blissfully unaware of how the simple gas valve on domestic boilers, furnaces and water heaters worked.
Until tonight, when my heating boiler refused to make any hot.
A quick check revealed no pilot, and my attempts to relight it were rebuffed. Pilot flame as long as I held the little red button down, but the flame went out as soon as I released it.
I knew that the other tube that runs to the pilot was used to prove that the pilot was lit. I figured it held a charge of some fluid that expanded and worked against a diaphragm in the valve.
Turns out that it's a thermocouple, and the voltage pulls in a tiny magnet valve.
Of course the home center is closed now. Guess I know what my first project is tomorrow.
Until tonight, when my heating boiler refused to make any hot.
A quick check revealed no pilot, and my attempts to relight it were rebuffed. Pilot flame as long as I held the little red button down, but the flame went out as soon as I released it.
I knew that the other tube that runs to the pilot was used to prove that the pilot was lit. I figured it held a charge of some fluid that expanded and worked against a diaphragm in the valve.
Turns out that it's a thermocouple, and the voltage pulls in a tiny magnet valve.
Of course the home center is closed now. Guess I know what my first project is tomorrow.





RE: I learned something new tonight
TTFN
RE: I learned something new tonight
RE: I learned something new tonight
So, thanks for sharing. I learned too.
rmw
RE: I learned something new tonight
While the millivolt output does not sound too impressive, they can easily develop a constant 100mA or more. That is quite sufficient to pull in and hold a solenoid valve.
The solenoid coil just needs sufficiently low dc resistance and the ampere turns that a pilot flame can develop will probably astound you.
RE: I learned something new tonight
In larger industrial gas burners the pilot is proven using a "flame rod", which is bassically a steel rod in an insulating holder (exactly like a spark plug with a long electrode.
A gas flame has the ability to rectify AC current into DC. An AC current is sent to the rod, and a nifty grey box looks for the DC current comming back.
RE: I learned something new tonight
My old dryer simply had mechanical leverage from the expanding probe to hold the pilot light valve open.
TTFN