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robbbb 07-12-2008 06:35 PM

Lennox G11 Pilot light with not relight
Hello All...

Well, Last night (9:02pm, Friday, July 11th, 2008) Our house got hit by Lightning.... Now as near as we can figure, as we cant find any actual physical evidence of the Lighntning hit (nor could the Fire Dept.), We think it hit some where near the chimmney.... The fact that the explosion from the lightning sent my wife and I like cats to the ceiling with claws extended was right and I mean right outside the window that we were sitting next too was a pretty good indicator that it was CLOSE...:eek: Course, all electricity went out, the breakers did thier job....

While I was making my rounds to see what and if anything was on fire or damaged when I went into the room in the basement where the furnace and water heater are there was the very clear smell of Ionized Air.
The Fire Dept checked very carefully in that area with the FLIR gun and could find no sign of fire in the walls or the chimmney. They gave the house an "All Clear" and we turned the breakers back on and everything pretty much came back to normal with the exception of the Cable TV Boxs, a DVD Recorder and my Home Theater... Were thinking the Cable system took the biggest hit from it....

Anyway... So today we go to take showers and my wife came out and said, "Um.. I ran out of Hot Water".... Soooo I goes into take a look, Sure enough, The Pilot Lights are out on the Water Heater and on the Furnace.. Baadabing, Badabang... 2 more Victims of the Lightning..
Got the Water Heater to relight, But I cant get the Lennox G11 to relight.
I did the Turn the knob off for 5 Mins, then move to Pilot and push down and hold while putting a match in and lighting the pilot gas, The Pilot lights, but after a min of holding it down, I then release it, the pilot goes out... did the same procedure again, this time holding down for 90 Secs, same result, tried one more time holding down 2 mins, Same thing....

So for those with more knowledge then I.... Whats Next? :whistling2:
Did the Lightning actually take out my Furnace?

Thanks in advance,

Thankfully in July and not January in Minnesota...

8 Ball 07-12-2008 09:03 PM

Try replacing the themocouple, if that doesnt work, you probably need a gas valve. Check your blower motor also. Have the safeties tested before winter.

robbbb 07-16-2008 10:58 PM

Sorry for not getting back to you sooner, work took me out of town for a few days.... is there anyway to check the thermal couple while its still in the furnace eg... voltmetering it for continuity or is it just a remove and replace thype of thing?...

Thanks for the leads...

After posting this, I got to thinking abuot what a friend of mine had said about looking for any signs of where the lightning exited... and I got to thinking about when I was looking into try to relight the pilot.... is it possible that the black was the lightning exit?


statman 07-16-2008 11:20 PM

You are overthinking the problem here....replace the thermocouple. It looks badly overdue anyhow....and no I dont think that is a lightning is soot caused by a poor burning pilot flame. Adjust it after you replace the thermocouple so it about 1-1.5" and it should be relatively blue (dont worry too much about color of the pilot but get it as good as you can)

robbbb 07-16-2008 11:27 PM

Ok will do that first...



fw2007 07-17-2008 08:24 AM

A thermocouple is an extremely low-impedance, passive device. Unless the current from the lightning strike traveled directly through the TC, I don't think it would have burned out.
IMO, the gas valve is a more likely culprit.
That said, I agree with the other posts in that you probably are due for a new TC anyway, and they are much less expensive than the gas valve, so it is the logical place to start.

Also, are you sure you have power to the furnace? The TC system usually works on 24V, which is supplied through a transformer, located in a box on the furnace.


fw2007 07-17-2008 09:45 AM

Sorry, I overlooked an obvious fact:
The pilot operates off the millivolt gas valve, which is driven by a hot thermocouple only. No AC is required to keep it open, as long as there is sufficient voltage from the TC.
The main valve, which is operated by the thermostat is powered by the 24VAC.

It might be possible to measure the output of the TC, but you will need a voltmeter that is capable of reading millivolts. I am not sure what the operating voltage for the millivolt gas valve is, all I know is that it's very low. It might be difficult to determine whether the TC is bad just by measuring it's output voltage, unless you have the specs.


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