Vermont Castings SDV30 NG Problem...pilot on, stove on, then pilot off the thermocouple and all off

[pkkmc96]

I have an old (but new to me) Vermont Castings SDV30 (serial number 7224) NG stove that I don't seem to be able to vent correctly--my assumption it is a venting issue not a parts issue. I get a solid pilot flame and the stove lights well, but after anywhere from 45 seconds to a couple of minutes (usually closer to the 45 second mark) the pilot flame is "drafted away" from the thermocouple until that side of the 3 way pilot assembly no longer has a flame and doesn't cover the thermocouple anymore...and then the main and pilot shut off. It seems to get wispy or thinner as well and sometimes wafts away before relighting on the 3rd axis that hits the thermocouple--the other two seem to keep a strong flame though they draft towards the front glass side. If I barely crack open the top of the glass, the pilot remains strong over the thermocouple and the stove stays lit. I'm using duravent 4" inner 6 5/8" outer and have 24" rise to a 90 degree before a 3' horizontal run to a duravent horizontal termination cap (46DVA-HC). Really getting frustrated because the are so few seams. I used a black fireplace and stove repair sealant at the exhaust collar at the top of the stove (dries hard) per the installation guide and high temp RTV (600 degree) red sealant for the inner and outer seams of the pipe and the terminal cap. Open to ideas or troubleshooting steps. Pictures of the pilot with the stove off and then with the stove on as it goes out. Thanks in advance for any help...at my wits end. Phil

 

[DAKSY]

You may have to disassemble the entire venting system to determine where the issue is.
It could be a blockage caused by an insect nest (i.e. beehive) or it could be a loose section of the
venting, allowing oxygen depleted combustion gases being reintroduced into the incoming air.
I would pull the cap & see if the venting is not securely connected there. Usually, the last section
of venting in the wall is a slip connection & if not secured with screws, can become detached.
If that isn't the area, then it could be a blockage in the stove body....

 

[pkkmc96]

Thanks Daksy I'll pull the venting tomorrow and recheck. If it's the stove body, do you have any recommendations for troubleshooting? I've used mirrors and lights to look internally, but don't have a flexible camera or anything. Thanks for the really quick response!

 

[DAKSY]

In order to check the stove body, you will have to pull the venting off the top of the unit.
One question: Is the pilot flame "agitated" at all where it encompasses the thermocouple?
It's hard to tell from the pic.

 

[pkkmc96]

Yes the pilot flame seems to get blown at times away from the pilot or wisp away...the axis that hits the thermocouple goes out first then the whole stove shuts down (as you would expect). When I get a chance today I'll take a video, pull apart the ducting, inspect the stove body, and put it all back together. I appreciate the help...I just didn't want to go through all that if someone had a different idea. Since it works with the glass cracked I figured it had to be a venting issue. Thanks again...Phil

 

[pkkmc96]

OK I pulled the venting apart and saw there was some light coming from the inner seams in the duravent 90 so I sealed those, resealed everything again, and checked the stove body exhaust and intake with no obstructions. Reinstalled everything with extra sealant to make sure there was no exhaust gases getting sucked into the intake...no change at all...didn't fix it. I've attached a couple more pictures and videos...any suggestions would be more than welcome! Thanks for the help, Phil

 

[pkkmc96]

DAKSY the flame definitely gets agitated almost immediately, thins and "blown" away from the thermocouple as soon as the burner is turned on...any recommendations to reduce that to see if that's the issue. I just rechecked the installation and ensured the horizontal run is level...shimmed to make perfect...no change.

 

[pkkmc96]

OK I just put a piece of aluminum foil as a shield on the "glass side" of the pilot assembly in a "U" that circles the thermocouple...and that axis of the pilot flame stays strong with the burner on...it appeared to be a venting issue because with the glass cracked it worked. In reality it appears the draft was too strong across the pilot assembly agitating the NG enough to go out only on the far side of the assembly. Now I just have to fashion a more permanent shield out of metal. For the record, I had tried to shield the pilot assembly but from the draft side...not the opposite side. I point that out because it really just needed a wall to slow down the flow from back to front...but putting the shield in the back did not work...providing a backstop on the "glass" side of the assembly did the trick. Thank you for this forum and all the help! DAKSY it was your comments on another post that got me to try shielding in different positions vice the obvious side of the draft...thanks my friend! Phil

 

[pkkmc96]

So the finished product was a 2" by 2" piece of galvanized 16 gauge metal bent with a 90 degree footer and cut a hole so the screw that holds the pilot assembly would also secure the shield. A 10 minute fix including waiting for the paint to dry after way too many hours pulling apart venting. Hope this helps someone in the future! Stove is working awesome now.