# Gas "wood" stove shuts off



## stevengrahek (Feb 19, 2018)

I have what looks similar to a Vermont Castings gas fired faux wood stove.  It was used, minus manual, and worked well for a year.  Then it started to go black inside from soot, and finally would just shut off after about ten minutes.  It has a "T" shaped pilot light, the base of the vertical part of the T goes out over the main gas channel, the top of the T goes Left and Right, one to a thermopile (with copper pipe back to regulator) and the other to a thermocouple with two lead electric going to the electric block on the regulator. 
Cleaned everything, including the thermcouple/thermopile, but still just shuts off after few minutes. 
Any ideas why??
thanks


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## DAKSY (Feb 19, 2018)

First of all, the ThermoCOUPLE is the smaller of the two & has a copper connection INTO the valve.
The ThermoPILE is larger & has the two wire connector to the terminal block of the valve.
If the unit is sooting, the air shutter - think air-to-fuel mixture - is closed too much. 
What fuel are you burning? LP or NG? The ATF  is different for each fuel...
When the unit shuts off, does the pilot stay lit?
Have you taken any milliVolt readings on the thermopile?
If so, what did you get?


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## stevengrahek (Feb 20, 2018)

DAKSY said:


> First of all, the ThermoCOUPLE is the smaller of the two & has a copper connection INTO the valve.
> The ThermoPILE is larger & has the two wire connector to the terminal block of the valve.
> If the unit is sooting, the air shutter - think air-to-fuel mixture - is closed too much.
> What fuel are you burning? LP or NG? The ATF  is different for each fuel...
> ...



THANK YOU for replying!  Right, I will remember to identify which correctly.  We are using NG, and I am pretty sure that is the correct one for this orifice, which I will go measure.  I did open the air inlet on the gas burner pipe which fits over the orifice, and it reduced the amount of the yellow in the flames.  But when testing the stove, after cleaning the thermocouple and thermopile, it still shut off after a few minutes, and both the main gas feed and the pilot gas feed shut down. 
I am not sure how/where to measure the millivolt readings, but will do so if you can tell me or direct me to directions to do so. 

Again, thank you.  Out here, all the fireplace shops/dealers will have nothing to do with any product not sold directly by them.
spg


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## stevengrahek (Feb 20, 2018)

stevengrahek said:


> THANK YOU for replying!  Right, I will remember to identify which correctly.  We are using NG, and I am pretty sure that is the correct one for this orifice, which I will go measure.  I did open the air inlet on the gas burner pipe which fits over the orifice, and it reduced the amount of the yellow in the flames.  But when testing the stove, after cleaning the thermocouple and thermopile, it still shut off after a few minutes, and both the main gas feed and the pilot gas feed shut down.
> I am not sure how/where to measure the millivolt readings, but will do so if you can tell me or direct me to directions to do so.
> 
> Again, thank you.  Out here, all the fireplace shops/dealers will have nothing to do with any product not sold directly by them.
> spg


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## DAKSY (Feb 20, 2018)

You will need a multimeter set to Volts DC, with 2 probes. 
Light the pilot.
Place the end of one probe on the screw at the RED terminal block (pic #2) marked TP - upper left. 
Place the end of the other probe on the TH-TP screw head - bottom center.
Read the milliVolts on the meter. With the pilot burning, the mV should be in the 475 - 550 range. 
Turn the burner on.
Read the milliVolts. They'll drop, but should be stable at about 190 - 220mV.
Let us know how you make out & we'll take it to the next step.


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## stevengrahek (Feb 20, 2018)

DAKSY said:


> You will need a multimeter set to Volts DC, with 2 probes.
> Light the pilot.
> Place the end of one probe on the screw at the RED terminal block (pic #2) marked TP - upper left.
> Place the end of the other probe on the TH-TP screw head - bottom center.
> ...




So I did the measurements as instructed, and it appears the first measured between 400-450; and then when I turned the burner on it dropped to 100-120.  That is right, correct?


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## stevengrahek (Feb 20, 2018)

DAKSY said:


> You will need a multimeter set to Volts DC, with 2 probes.
> Light the pilot.
> Place the end of one probe on the screw at the RED terminal block (pic #2) marked TP - upper left.
> Place the end of the other probe on the TH-TP screw head - bottom center.
> ...


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## stevengrahek (Feb 20, 2018)

stevengrahek said:


> So I did the measurements as instructed, and it appears the first measured between 400-450; and then when I turned the burner on it dropped to 100-120.  That is right, correct?




I meant, that isn"t right.


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## DAKSY (Feb 20, 2018)

Yeah...Not good...Sounds like you need to replace the Thermopile...
About $50 for one called a universal MilliVolt Generator at True Value.


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## coaly (Feb 20, 2018)

Wow, after 25 years servicing gas equipment I never asked anyone where they bought an appliance, I was just there to fix it !

DAKSY will be along to help you out, so I'll try not to confuse you or get in his way . Your reading with pilot lit only is the no load voltage being generated by the Thermopile. That current is used to open the burner valve with a electromagnet in the valve, so with it on, you're reading the voltage drop from the current being used through the coil that makes the magnet. (as well as wiring and thermostat if wired to open gas valve) Since the pilot goes out as well, that is the current from the thermocouple that holds the safety valve open when heated by the pilot flame. Make sure when the main burner is lit the pilot is still strong engulfing about the top 1/3 of the thermocouple. A weak pilot can be thrown off course and not continue to heat the thermocouple properly. Voltage generated by thermocouple energizes an electromaget coil that holds the safety open. (what you hold in when lighting until it is generating enough current so the magnet holds it open for you when you let go)

Is this connected to a proper vent of the correct height? Most will have a large air intake at the bottom of exhaust vent called a diverter. It allows cool air up the pipe to cool and slow the draft. It should have a safety switch in the indoor airflow stream that is a temperature switch used as a exhaust spillage switch. It is designed to shut the gas off coming in the valve by breaking the current flow from thermocouple to valve. Make sure all heated exhaust is rising up the stack and not spilling out at the diverter. This safety switch is designed to heat the spillage switch when not drafting properly and shut the unit down like you're describing.

A simple test is to light the main burner and shake out a match to watch the smoke rush into diverter and up the stack. It shouldn't linger and stay in the building. When a main burner is first lit with a cold stack some spillage is normal until it heats the stack and starts drafting. That doesn't explain why it worked for a year unless something has changed with the venting system.


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## coaly (Feb 20, 2018)

He beat me to it.
DAKSY, are you sure the thermopile holds the safety open? Sounds like the safety valve is shutting down and the thermopile should only operate the main burner??
Difficult not being there looking at the wiring.
Easy way to tell is remove one of the wires from thermopile and the safety should still hold pilot on. If it does, thermopile only works main gas valve. Obviously the main burner will not light with wire removed.


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## stevengrahek (Feb 20, 2018)

Thank you all for advice.  Will try replacing the thermopile. 
will let you all know what happens in a couple of days.


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## coaly (Feb 20, 2018)

You stated when it shuts down the pilot goes out. That should have nothing to do with the thermopile. You can check it easily by removing one of the wires on the gas valve from thermopile. If pilot stays lit, the thermocouple is generating the power to hold safety open. I believe your thermopile only supplies power for the main burner. If the pilot goes out when the problem occurs it is due to the pilot safety system. (safety stops all gas flow through gas valve) The thermopile failure will only prevent the main burner from lighting. (the pilot would stay lit)
Do you know the make and model so we can look at a schematic before you spend $50 for a part you may not need?


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## DAKSY (Feb 21, 2018)

I missed the pilot also extinguishing, but the mV on the thermopile is WAY TOO low. 
Like you said, not being there makes it a little hard to diagnose. 
To the OP is the unit a DV - pipe within a pipe, or is it a B-Vent - single 4" diameter pipe?


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## coaly (Feb 21, 2018)

But we don't know how long it was lit before testing. I've seen some take quite a while to creep up and be up to 750 mv after five or ten minutes.
Then we don't know how long the thermostat wires could be, measuring the voltage drop not only from coil but through wires and switch points....... AND we're not looking at the strength of his pilot. Nothing like being there.


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## stevengrahek (Feb 22, 2018)

so sorry to have dropped out.  had a 16 hour work day yesterday, and another tomorrow.  but will try to put a more coherent package of data together, including a schemata of the wiring, pictures of all relevant items (What I think are relevant, but I am not that knowledgeable, obviously).  It is hard working on an appliance that has no name plate, serial number, nada.  Only stickers are some traditional warnings, and one Made In Canada label, but no Branding.  And of course, no manual.  However, I know it is not a cheap knock off, if a knock off at all.  Please hang in there until I get the info  better organized. 

I really appreciate all your help. I've never used a forum, and find it, actually, exciting. 

thank you,
steven


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## stevengrahek (Feb 22, 2018)

Hello again.  Already pictured above is are shots of: gas valve; pilot carriage with the thermopile and thermocouple and pilot gas line and ignitor; 
Also, a shot of the gas orifice.  We have been using NG and it worked fine for one season, then the sooting and shutting off started. 

Give the size of the orifice, I am pretty sure it is for NG; sadly, no markings on the gas valve can be found. Although when one looks at the robertshaw 710 series installation data sheet it appears my valve has a regulator conversion kit 1751-007.  I will post the pdf for that sheet.

also, I will post my verbal schemata of the wiring for the unit.  if needs be I could try to diagram it. but it is pretty straightforward.

finally I will post some more pictures of various aspects of the unit.  I know it must  be direct vented, and sealed (as per a label on the back), and the equipment we used was supplied  by a stove store, so I have assumed it is correct.  But,....?


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## stevengrahek (Feb 22, 2018)

here is the verbal wiring info:

There is a thin metal cover plate over the back of the stove, sitting above the blower fan (which is a two unit system)

The blower fan has a standard 110 v polarity two plug (i.e. no ground) lead that plugs into a 110 v single gang box with two receptacles. 

One of thess receptacles is hot wired that is, if you plug the fan into it, it turns on, and only turns off if it is unplugged ( and indeed upon inspection this receptacle is directly wired to the incoming supply (both hot and common); 
the other is not hot wired (would assume the other is driven by the thermostat, and in fact the "hot" side of this receptacle comes from the round sensor device's blue clip side, while the common goes to the general common wire nut inside the gang box?) The box has a incoming standard polarity two plug line that goes to the wall of the room.

There is an ON/OFF rocker switch at the top of the cover plate.  And a circular dial with white line on top mounted somewhat below it; 
both easily accessible by reaching around the side of the stove.   The circular dial turns on with a click and can rotate about 3/4 of a circle, and turns off with click without further rotation.

On the inside of the cover plate near the bottom, there is a flat round device (see pictures) which I assume is some form of sensor (?heat).

WIRING
All wires are heavy coated, presumably for protection from heat. 

A black wire goes from the "ON" switch terminal to gas valve Red Terminal TH screw.
                                                                                                            TP

A black wire goes from the "OFF" switch terminal to gas valve Red Terminal TH screw.

The wire two lead wire coming from the Thermopile goes to Red Terminal and one lead shares the TH screw,
                                                                                                                                              TP

The other white lead goes solo to the TP screw. 

There is an orange wire connecting the piezoelectric device from push button at the gas valve, to discharge unit at pilot carriage.

The black dial with white line on top has a black wire goes into the 110 volt single gang box and joins the other wires under the hot incoming lead wire nut.

The hot incoming lead wire nut feeds the always hot receptacle too.  The common incoming lead feeds both receptacles.

The other side of the black dial has a black wire that goes into the black round sensor device, while the other side of that device has 
a black wire (blue tipped) that goes to the 110 volt single box and is the sensor controlled hot side of the sometimes hot receptacle. 

PILOT CARRIAGE
The pilot gas tube runs form the pilot outlet above the inlet wrench boss on the gas valve to the pilot outlet burn point, shooting
a flame up against a metal diversion hood, which shoots the flame left to the thermocouple, and right to the thermopile, as well
as forward over the main burner tube. 

The thermopile has the white two lead wires coming from the bottom of it, and goes as noted above.

The thermocouple copper tube comes from the gas valve thermocouple inlet and goes to the pilot carriage.


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## DAKSY (Feb 23, 2018)

***On the inside of the cover plate near the bottom, there is a flat round device (see pictures) which I assume is some form of sensor (?heat).***

I don't see that in any of the pix...

I'll ask again - Is this a Direct Vent or a B-Vent unit?


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## coaly (Feb 23, 2018)

All 100 V is for the blower. The gas valve is a millivolt style. One recept. is controlled by the thermostat switch called a thermo-disc switch. It will have markings of F for Fan and temperaturefor on and off. a switch with F is normally OFF and turns ON with temperature rise. The blower should only run when the stove is hot plugged into the other recept. This has nothing to do with the unit shutting down.

Need to see the switch in air intake of divertor hood. (If it is what you describe at bottom of plate) If you can see it, see if there is a L on it with numbers. That stands for Limit. If so, it is normally ON until hot when it shuts OFF. That is the spillage switch to shut it down when not drafting correctly. Follow the wires from that switch and see if they go to the gas valve where the metal line connects from thermocouple. You can test to see if that is the spillage switch by removing one wire from it, and try to light pilot. It should light and go out when you release pilot knob. That will tell us if it is the pilot safety spillage switch.

Direct Vent means the heater gets combustion air from outside and the exhaust will be double wall with hot exhaust escaping from the center and cold intake air coming in the outer chamber. B-vent is a twist type lock together pipe with only hot exhaust flowing up through it above roof line.


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## stevengrahek (Feb 23, 2018)

sorry about pictures.  am having trouble getting them from phone to computer.  and can't address that today (16+ hour work day, but then have some days off).
it is a direct vent for sure.  also, I don't follow everything coaly is saying.  but will get the pics out tomorrow (got to, it's cold here right now )

thank you


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## stevengrahek (Feb 24, 2018)

stevengrahek said:


> sorry about pictures.  am having trouble getting them from phone to computer.  and can't address that today (16+ hour work day, but then have some days off).
> it is a direct vent for sure.  also, I don't follow everything coaly is saying.  but will get the pics out tomorrow (got to, it's cold here right now )
> 
> thank you


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## stevengrahek (Feb 24, 2018)

FYI: THE only wires to/from the gas  valve are those as stated in my written wiring schemata pdf above.  There are none from one part of gas valve into another part. 

spg


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## coaly (Feb 24, 2018)

Notice the F on the switch you pictured. That is the FAN switch as I stated above. All that wiring outside of the burner area is 100 volt for the blower.

What makes the parts work that are causing the problem of shutting down is the* thermocouple* circuit.

When you light the pilot, one of the pilot flames heats the smaller of the two "generators". (that is the thermocouple) Inside that small tube the flame should cut across (thermocouple tip) is a piece of metal that bends when hot against another dissimilar metal contact inside. This generates a small electrical current inside a conductor which is inside the metal tube which is the "power" feed from thermocouple to gas valve. When you light the pilot, you have to press the pilot knob IN to open the valve that allows gas to flow through the valve. While holding it in, the heat from pilot flame bends the contacts together in thermocouple which creates enough current to energize a electromagent in valve. This magnet then holds the valve open for you when you let go. (a steel rod you were holding against spring pressure)
As long as the correct heat is being supplied the gas valve remains open allowing gas to flow. If anything causes a drop in voltage to valve, it closes with a click and shuts gas off through valve. This is what is happening when it shuts down.

If you don't understand that, go no farther and ask.

If this appliance were a normally vented gas stove that used INDOOR air for combustion, it would have a safety switch on the thermocouple line (the switch with "L" for Limit) in the air intake for the exhaust flow. This is to shut the valve off in case of CO leakage into home. You don't have that on direct vented unit since there is no communication with indoor air and the burner.

Since your problem is after 10 minutes of operation, is that 10 minutes of main burner operation, or does it go out if* only the pilot is lit* for a period of time as well? In other words, if you only light the pilot and leave control in pilot position, does it remain lit ??


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## stevengrahek (Feb 24, 2018)

coaly said:


> Notice the F on the switch you pictured. That is the FAN switch as I stated above. All that wiring outside of the burner area is 100 volt for the blower.
> 
> What makes the parts work that are causing the problem of shutting down is the* thermocouple* circuit.
> 
> ...


I do understand what you wrote, thank you for being so detailed. 
Re when does the stove shut off, I wanted to test that, so I lit the pilot, and no more.  The pilot stayed lit for two days. Then, when I flipped the switch to on, the burner immediately lit.   However, in about two minutes now, it shut down the whole pilot system, i.e. the burner went off, the pilot lite went off.

NOW, one more variable.  The dial on the gas valve, a metal dial with lo --- hi stamped on it, and is more centered next to the black plastic gas valve dial that is held in to start the pilot.  That metal dial spins freely, meaning the plunger button inside the dial is moved either in or out. 
Is this contributing to the problem too?

Do you agree the orifice is indeed for NG?

thanks

steven


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## coaly (Feb 24, 2018)

The control with hi and lo only controls how much gas flow goes to the main burner when that portion of the valve is ON allowing gas flow to main burner. It is how much heat is produced by the main burner and how much heat will go into the building.

The orifice size measurement is more critical than a picture would show. It may be stamped with a number or you would measure with a drill bit until you know the exact size in thousandths of an inch. If it was a propane orifice you would have very small flame to none at main burner. The orifice size is twice as large from LP to Nat. Your burner should be BLUE down at the bottom of flame at burner and only have yellow tips. If so, it is the correct orifice.

Back to your problem;

You should be able to troubleshoot what is wrong with just your eyes.

The PILOT should be all blue. Which is critical for keeping the thermocouple generating the proper current to keep gas valve open. With pilot only on, it is doing that as it should.

Look at the flame as it cuts across the thermocouple with pilot only lit. This is the correct flame generating the correct amount of voltage to keep the gas valve open as it should.

Now turn on the main burner and watch the pilot flame. It should stay the same, not waver,* not move away* from the thermocouple.

IF it does, you probably have an air leak from around the glass or some other leak into the burner "chamber" rushing into the combustion chamber area. This will allow the thermocouple to cool down and shut the gas flow off through valve. Lets verify if that is what is happening first. Simply watch the pilot flame to see how long it remains lit before shutting down.


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## stevengrahek (Feb 24, 2018)

OK.  It is definitely a NG orifice.  The  burner flames are blue based with yellow tips.

The pilots are blue flame, but they do flicker a fraction of a second, about every second.  Could this be the cause?  The pile and couple both seemed to be engulfed in flame.  I will try to take a video tomorrow and post it.

about that hi lo dial.  yes, that what I thought it was for.  however, when dial is attached with the center screw the dial swings without catching anything.   if the dial is removed, and then the plunger unit that screws into that inlet is removed, the flame goes to low, but if the plunger unit is screwed back into the inlet, it goes to high.  and there is no way to get it down using the valve.  
anyway, not that important if it is OK to have it on high all the time?

spg


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## coaly (Feb 24, 2018)

Yes, it can remain on high........

The portion of the valve that works the safety is the black plastic knob. When in pilot position it pushes inward which moves a steel rod inward with a spring pushing it back out when you let go. When the thermocouple is generating electric current, the electromagnet inside the valve holds the steel rod "IN" so gas can flow through valve. You're generating enough current to hold the valve open as well as generating enough current to open the main gas valve with power from thermopile. So the pilot flame is hot enough to generate enough power.

The glass must be in place to light this appliance, not leak around the edge, and make sure where the pilot line comes through the box into burner chamber there is no indoor air leaking into burner chamber. That will cause the pilot flame to move around when main burner is lit and not be in the correct position heating the thermocouple correctly when main burner is on.

I'll explain in my next post how a direct vent appliance gets oxygen into the sealed burner chamber for oxygen to get to the pilot and main burner. Then you will know what to look for.


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## stevengrahek (Feb 24, 2018)

Hello again.  Am afraid I am too much the amateur, in that, I have been testing the system with the fire box removed from the cast iron casing, and not always with the vent pipe re-attached.   Doing that will invalidate the results, right?  because air comes down and messes with the Pilot?

This stove is designed without access from the front when it is in its cast iron casing.  So I have to remove the box, then remove the glass plate on the front to access the pilot, burner etc. 

I did go on line and found a Vermont Castings generic manual, and it seems to be accurate for the configuration of the valves, pilot carriage etc. for my stove. 

file:///F:/Drive%201/aaSteven's%20%20documents/6900%20GRASSWOOD/2016%20ART%20STUDIO%20REMODEL/Gas%20fired%20woodstove/vermont%20casting%20manual%20very%20similar%20to%20ours.pdf

but of course the valve has updated hi lo type switch, as far as that dial is concerned.   and I believe the gas valve terminal block is updated but just vis a vis the type of connectors used, not the actual terminal labeling.

spg


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## coaly (Feb 24, 2018)

The difference between direct vent and using indoor air with a chimney pipe opens an entire complex scenario with other factors to consider.

A gas burner is normally in contact with the atmosphere such as a range top burner or BBQ grille burner outside. When you put a burner inside a sealed burner chamber, it no longer has free atmospheric air pressure to push into it. I'll explain;

Any gas burner has a mixing tube portion of the burner. After the gas comes through an orifice, raw fuel mixes with oxygen in the mixing tube portion of the burner, before coming out the small holes where it is ignited. Gas comes through orifice at the correct pressure provided by a pressure regulator. AIR enters due to gas pushing the air (atmosphere) out of the burner tube. *Atmospheric air pressure* PUSHES air into burner to mix with fuel. This intake of air is at the air intake adjustment of burner. This is the basic flow that must happen to have proper combustion from any naturally aspirated gas burner. (aspirated from atmospheric air pressure, not a combustion blower which you don't have) Even a small pilot burner has a mixing tube with an air intake hole because raw fuel won't burn until mixed with oxygen. (roughly 70:1 ratio)

When you have a burner inside a chamber sealed from indoor air, you no longer have atmospheric air pressure to push air into the burner to mix with fuel. The venting system (exhaust out, air in) must be engineered to work properly.

Hot exhaust gasses rise, so it is critical to have enough vertical rise in the exhaust configuration to create movement upward and out of the burner chamber. This upward movement is measured in *draft *which creates a low pressure area in burner chamber which allows the higher atmospheric air pressure to enter (push) into intake, bringing fresh oxygen into the burner chamber. This is where the oxygen for mixing with fuel comes from.

If venting is not correct, you no longer have atmospheric air pressure at air intake of burner. The gas coming in can't get enough oxygen to mix with the fuel causing a rich air / fuel mixture which is where the black soot comes from. Too much fuel, not enough oxygen. In your case, this is configured by the manufacturer and would be specified in the installation manual as how much rise is required and how much horizontal run would still allow the correct amount of draft to create the proper intake air pressure. We don't know the exhaust / intake configuration to tell you if you have the correct amount of oxygen getting to your burner. So you can only go by how much yellow flame you have. Blue is hotter and burning clean, yellow is carbon or a carbonizing flame which deposits carbon in the form of soot on any cool surfaces it comes in contact with. This can be the glass, logs, or vent. As you know it makes a mess. The blue flame should be enough to clean the unburned fuel in the yellow flame to prevent carbon accumulation.

Now, on to your problem; When the main burner is on, we have a low pressure area being created by the draft exiting the chamber. This will allow the higher atmospheric pressure in the home to PUSH into any opening it can which will be the cause of the pilot to waver and not heat the thermocouple correctly. It's like getting a blast of air causing the flame to no longer be correct to heat the thermocouple correctly. That is what I'm suspecting is happening. It is the most likely cause and common when there is an air leak into burner chamber.


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## coaly (Feb 24, 2018)

You posted your last post as I was composing that book, so Yes....... it has to be installed in the sealed burner chamber.
(someone help DAKSY off the floor )

It becomes more complicated being direct vented, but you should understand the principals to install and work on it.

Going back to venting to get the proper air into the sealed chamber;
Your picture shows a minimum amount of rise that may or may not create the draft required for the proper flow out and back in.
It would have been better raised higher to create more draft. That may be the cause of sooting due to lack of oxygen. I didn't look at the VC manual, but vent configuration requirements would probably be close to that manual.

Was soot on the vent or outside as well? That's a sign of improper venting. Units comparable to yours that I've installed have needed to be higher.


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## DAKSY (Feb 24, 2018)

I'd say it's the correct orifice. That's not the cause of your sooting. 
Generally it's the air shutter on the origin of the burner.
It regulates the combustion air mixing with the fuel to optimize the Air-to-Fuel ratio for the presentation of the flame.
LP and NG burn blue. As you close the shutter & reduce the ATF, the flames get yellower (LEANER)
If the shutter is closed too much, not enough O2 mixes with the incoming gas...It runs RICH...
It can also be caused by mis-positioned logs, lava or glowing embers. 
They also mess with the combustion, but in a smaller way
The third cause can be in the venting, if it's incorrect or is malfunctioning...
Exhaust gases can be drawn into the combustion side & the spent oxygen screws with the ATF,
again by causing a RICH condition...


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## stevengrahek (Feb 27, 2018)

OK. thank you for hanging in there for me DAKSY AND coaly.
I returned the firebox to the cast iron casing; making sure it was air tight as possible.  hooked up the direct vent, which is a one foot vertical riser from top of unit, 90 elbow, one foot to wall receiver.  according to the Vermont Casting manual I am subbing for lack of one, that is acceptable, ie above black cut off line, but in a gray zone.  and yes DAKSY, those pipes have a lot of fine black soot inside them (so maybe I need another foot or so of rise (more horizontal pipe would be problematic for this installation, but vertical can be accommodated)?

The stove pilot lights and burns as in attached video.  Lights up the main burner, which settles down into a yellow tipped blue flames.  Everything is wonderful, for about 20-30 minutes, and bam, all gas gets shut off.   

So?  Are the millivolt readings being low still a possible problem.  Should I try the readings after about ten minutes of the main burner being on?

Is the soot in the stove pipe an absolute indicator of need to increase vertical pipe?  (I have added more air at the orifice area, and the flame seems to bluer than previously.  So maybe less soot being made, and only the thermocouple/pile is the problem?).

have order new webbing to be sure glass front seals completely, but are those small yellow tips really an indicator of air seeping in?

thanks for any help you might suggest. 

steven


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## DAKSY (Feb 27, 2018)

Watch the flames. Do they seem to be "lifting" off the burner (aka ghosting)?
If so, that may be an indicator of your problem. 
A blockage in the intake side (outermost diameter) of the venting.
Make sure it's clear & the exhaust side (innermost diameter) is securely attached...


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## coaly (Feb 27, 2018)

I don't believe 1 foot rise is near enough to make enough draft to get air into the burner chamber. (same as a blockage not allowing air in) I would personally make it about 3 feet rise with 1 foot horizontal if possible...... Lack of air not only creates soot, but affects the pilot with lack of oxygen. When it's burning on high, take note of the pilot flame. Does it look exactly like it does when pilot only is on? It may "lift off" the pilot burner or even go out. If this happens, current from the thermocouple ceases and the safety valve closes.
Black soot and going out, I'd guess it to be starving for air since the pilot looks good and thermocouple generates enough when only pilot was lit. 

The thermopile in your unit creates electric current to open main burner valve. So if that is weak, the main burner will go out or not light.

The thermocouple creates the electric current to hold the safety valve open, which is what is closing when the entire unit shuts down. We know it is generating enough current when only the pilot is lit since the electromagnet held the safety open for 2 days. Something is allowing the thermocouple to cool enough to not produce enough current to hold the safety open. You should be able to see it, such as the flame tip bending and not cutting across the thermocouple tip. Also the pilot flame may get yellow tips with main burner on.......The pilot looks plenty strong in video.

You could also try timing it on low or medium flame. When this appliance was working, was the burner control set to high? The higher setting will consume more oxygen and possibly not make much more draft (lower pressure area in burner chamber) to compensate for more needed air.


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