Heat n glo shutting off abruptly

[Cjschwal]

Hello Hearthers,
I have a Heat N Glow Vienna 1 model that’s absolutely killing me. The system pilots and starts as intended but then abruptly shuts the gas solenoid valve off after 3-5 mins. I noticed the new pilot flame is less robust than the prior. Frustratingly, the pilot flow adjustment does nothing in either direction. I have disassembled and cleaned the stack- no obstructions and good outside air comes into the firebox. The main burner ignites after toggle “on” and has robust flame - almost too much. I’m thinking the thermal high cutoff switch is the culprit…but I’m not sure what changed. The summary symptom is the solenoid valve closes after 3-4 minutes consistently. I am tempted to bend the thermocouple closer to the pilot but don’t want to break it. It could be he thermocouple isn’t maintaining its signal.

What am I missing here? Is there a scenario where the thermal cutoff switch lowers its threshold? Replace the switch and see what happens? Thanks I’m advance!

 

[DAKSY]

Take a reading on the thermopile with a multimeter set to volts DC, with the burner off. Record it, then do the same with the burner on. Let us know what mV readings you get.

 

[Cjschwal]

Take a reading on the thermopile with a multimeter set to volts DC, with the burner off. Record it, then do the same with the burner on. Let us know what mV readings you get.

 

[Cjschwal]

Thanks Daksy for the quick reply. Turns out my thermopile is a drifter…starts at 0mv cold then up to 402 with pilot. I can hold ~400 indefinitely. When Stove switch / main burner goes on, that drops ‘er to 160 where she slowly drifts down over the course of six minutes to 138 before shuttin’ ‘er all down (g’night). I get tired after a long day too but six mins is a lil shy of expectations. What would cause a slow drawdown like this? Thermopile (and pilot Assy) is only 36 hours old. Thanks again

 

[DAKSY]

The thermopile is probably bad from the factory. Electrical components are sometimes “hinky” like that. They fail when they want to, no matter how old they are. Replace it & you should be ok. Let us know how you make out.

 

[gthomas785]

Is it possible that your "robust" burner flame is creating a draft that pulls the pilot flame away from the thermopile? Unlikely, but I've seen it once or twice.

 

[Cjschwal]

Update for mods - please disregard my last post from 45 mins ago that’s in review. I discovered my thermocouple was the issue - it was not positioned close enough to the pilot flame. After I repositioned it, thermopile voltage holds steady at 180mV. Prior to TC repositioning it was eroding slowy over to the cutoff voltage (140 for me). Cheers!

The thermopile is probably bad from the factory. Electrical components are sometimes “hinky” like that. They fail when they want to, no matter how old they are. Replace it & you should be ok. Let us know how you make out.

Issue resolved! I gently bent the thermocouple toward the pilot flame. I have seen this on other similar stoves. I did the same for the TP while I was in there. No more voltage erosion and all is well. I suspect the real culprit is the pilot assembly is pretty lame when it comes to flame. It’s not OEM and I’ve peed with more flame than it provides (yeas it was 1980s spring break). I am upset with my SIT-820-NOVA’s lack of ability to adjust pilot flame. Oh well I took matters into my own hands and all good now but I will follow up with the non-OEM pilot Assy manufacturer. Sheesh. Thanks hearth dot com experts I almost had to call in sick with a mental health day.

 

[gthomas785]

If the pilot is weak and can't be adjusted higher, the pilot tube could be clogged. Take it out and blow some compressed air through it.

 

[Cjschwal]

If the pilot is weak and can't be adjusted higher, the pilot tube could be clogged. Take it out and blow some compressed air through it.

 

[Cjschwal]

Good call will try that before I reassemble the valve trim plate

 

[Millbilly]

I have never seen a clogged pilot tube. Focus on cleaning the pilot orifice and hood. Use pipe cleaner and a little pilot puffer. No need for carb cleaner or anything fancy.