Jotul Allagash 3 pilot dropped out after 1 1/2hr

[kc classic]

Hello All,
I found this forum after research what I thought was my problem. Here it is: I have the Jotul Allagash 3.
I can light the pilot and it will stay on. I left it on for 2 days no problem. Then I turned on the main burner and after 20 to 30 minutes both the main and pilot flame dropped out.
At which time I took the stove apart and cleaned the thermocouple and thermopile. I checked the pilot orfice and cap. I also tightened the thermopile in the housing. Also checked the main burner orfice. Then put it all back together.
So I did the millivolt test. Thermopile readings from a cold start went to 650 and dropped back to a maintained value of 567. Then after firing up the main it dropped to 260 and maintained at 246, eventually dropping to 210. Then I used the wall thermostat to control the burner and the reading went up to 232.
I ran it for 1 1/2 hours and had no problems. Thinking that I had it fixed I turned off the main burner. Ten minutes later I heard a click and checked to see the pilot light had dropped out. At that point the millavolt reading was 400.
Can anyone tell if it is the thermocouple or the thermopile?
Thanks in advance for any info.
kc classic

 

[DAKSY]

Not from here! Just kidding. I'm not sure if you're getting the same winds
as we are to the east of you, but they can wreak havoc on a thermocouple's
function.
A little bit of a breeze agitating the pilot flame will cause the millivolts to drop & the pilot will shut down.
The millivolt readings on your t-pile are good. Have you taken a reading on the t-couple when it's under the pilot flame?

 

[kc classic]

I will check that next. I can check that by connecting to the copper line and the fitting that goes into the gas valve , right?

 

[kc classic]

Actually not all that windy here.
Alright, I connected to the copper line from the pilot and the fitting going into the gas valve and got little to no reading.

 

[DAKSY]

Disconnect the t-couple from the valve.
You will need alligator clips on your multimeter probes to
perform the test, unless you have a helper with you.
Attach one clip on the enlarged "button" that seats in the valve
& the other clip on the copper tubing an inch or so away from the button.
Ignite the pilot & hold the pilot knob in to keep the flame on.
Read your numbers...
You should be somewhere around 28mV

 

[kc classic]

got it, will do

 

[kc classic]

I got a reading of 27

 

[DAKSY]

I'd say your t-couple is fine.
Is the top 3/8" of the t-couple engulfed in the pilot flame?

 

[kc classic]

Yes, I am running the stove now. Will let it burn for an hour and turn off the main burner leaving the pilot light on. Then see if the pilot drops out. I have 288 on the thermopile right now

 

[DAKSY]

Ok. Keep in touch.

 

[kc classic]

after I hr 23 minutes I had 276 mv, I shut the burner down leaving the pilot lit. The mv jumped to 544.
I am now waiting to see if the pilot goes out after a few minutes

 

[DAKSY]

Those numbers are normal.

 

[kc classic]

It went for 1 hr and 10 minutes and did not go out. I just turned the burner back on.
When the burner was off the reading went from 544 up to 673, before I turned the burner back on. The mv are staying high this time, 430- 10 minutes after the burner being back on.
Seems to be working now.
I will post back if it goes out again.

 

[DAKSY]

That's pretty high. Most t-piles are rated for 750mV,
but will burn out at that reading. Maybe your t-pile is on its way out,.
but that still won't account for the pilot extinguishing...
I would turn the pilot down to the 550mV range with the burner off.

 

[kc classic]

Has been working all afternoon now. I will check the mv with another meter later. the pilot flame appears to be what the manual says it should look like.

 

[kc classic]

After running for a couple of hours this evening, I shut it down. I left the pilot lit and after 20 to 30 minutes the pilot light dropped out again.
What's next, change out the thermocouple?

 

[DAKSY]

I guess I'd try that. They're inexpensive enough.
Just for grins, tell me what you have for venting.

 

[kc classic]

this is a b-vent system. I installed it many years ago. The last couple of years it has been doing this where the main burner and pilot would drop out.
I finally got around to trying to diagnose the problem.

 

[kc classic]

It has a short piece of 4" horizontal pipe that goes into a 2 story vertical chimney (4" pipe in a 8" metalbestos pipe).

 

[DAKSY]

AHA! B-vent systems have another component in the safety system.
Somewhere in there is a snap disk. That could be the culprit, & also
the wiring to & from it. If the sheathing fails on the 18 ga. wire, it can
ground out against the cast iron stove body. Other than those, this one
is baffling.

 

[kc classic]

I just pull the thermocouple and thermopile out. Trying to source the parts now. I will go back and look for the snap disc.

 

[kc classic]

I am assuming the snap disc in the gizmo in the back of the stove where the flue pipe connects. Of course that is the easiest piece to get to.

 

[kc classic]

Ok I am about to give up (not really). Had the thermocouple and thermopile out today. Then you told me about the snap disc. Figuring that was the problem, I put the rest back together. I put a jumper on the snap disc to test things out. Now the pilot light won't stay lit. So I checked the thermocouple again and only came up with 14 to 15 mv. Then it started jumping around on voltage.
So I am going to get another tc and try that.

 

[kc classic]

put in the new thermocouple today. Pilot would not stay lit. Went back and checked. Found where the tc connects to the gas valve there is plastic piece with a wire connected to it. That had slipped out when installing the tc. Have been using it for 4 or 5 hours now and things are good.
Thanks for all the help.

 

[kc classic]

worked for 3 days. Shut the main burner down and the pilot went out. Relit the pilot and turn the main back on. After awhile the whole went out. Back to square one.