Vermont casting PDV20 lighting issue

[PaulRV6]

The fireplace has been working ok and this AM the pilot went out (it was also very windy last nite). I went to lite it and it took awhile but got it lit. When turning the knob from pilot to on the pilot would go out. This took me 5 or 6 times before it finally stayed lit. Is this normal or do I have an upcoming problem. It seemed like I had to hold the pilot button in quite hard and if I moved it slightly the pilot would go out before being warmed up. Do I have a TC issue? Thanks for any help yu can offer.
paul

 

[DAKSY]

How old is the unit?
Are you burning NG or LP?
Is the TC clean?

 

[PaulRV6]

Purchased it in 2001 for NG. The TC was replaced once before. It looks pretty clean but not sure how clean is clean? Where do I check for proper voltage output of TC? I went across the bottom TH term and ground and got 2.3 - 2.5 MV reading with pilot lite on but not sure if that is correct. Book says "MV meter should read greater than 10MV" but doesn't say where to test. There is a good flame on pilot. I tried to adjust pilot with adjusting screw 1/2 to 3/4 turn but didn't change the flame so left it alone. Thanks

 

[DAKSY]

As long as there is no carbon build up on the TC, it should be clean enough.
In order to check the mV output, you need to disconnect the end that is threaded into
the gas valve. Set your probes on the copper wire & at the extreme end of the TC.
You will need alligator clips if you are doing this alone, as the TC needs to be in the
pilot flame in order to get mV generation. Your readings should be above 28 mV...

 

[PaulRV6]

Bob, not to make this difficult but at the extreme end I think is a nut, is that where I should clip on to? One lead is on the OD of the copper tube and the other is on the nut? Wouldn't this just short out the reading? What am I missing? Thanks

 

[PaulRV6]

I also want to mention that yesterday all of a sudden the fireplace went out meaning the pilot and the main flame. I haven't tried to lite it again until I hear back from anyone. Is this pointing to the thermopile? Thanks

 

[PaulRV6]

Hi, Anyone have suggestions for me? I am going to test the TC and TP to see what the voltages are. I think the volts should be btw 10 and 28 mv for the TC and min 325mv on the TP with main switch off and 110mv min with switch in the on position (can someone explain why the drop when switch is turned on)? Can you also confirm these are correct voltages? Thanks

 

[PaulRV6]

Hi again. Could someone advise on the questions I posted about the voltages and possible thermopile problem? Thank you.

 

[PaulRV6]

In case anyone is interested in looking at this but I did more testing on this and the pilot stays on so I believe the TC is ok. At first when I would turn the knob to on (from pilot) the pilot flame would go out. This took a few times and it finally stayed on. I'm not sure what causes this?
So I hooked the meter up to the TP/TH terminal and ground and was getting 550 MV with switch off and with switch to on it would read 275 MV (with glass off). Put glass on the front and Thermopile readings were 610 MV in off position and on it read 285 MV and in thermostat position read 290 MV.
Are these readings acceptable? I cleaned the TC and thermopile with emery paper and the readings didn't change much. The unit is working now in both the on manual position and the thermostat but I'm not sure for how long. The last time it went out was about 1/2 hr after lighting unit. Thanks for any input from the experts.
I was thinking on just buying a new thermopile to have on hand in case you say that is what it needs, and I will put it in, but just not sure. Thanks

paul

 

[Lennox65]

In case anyone is interested in looking at this but I did more testing on this and the pilot stays on so I believe the TC is ok. At first when I would turn the knob to on (from pilot) the pilot flame would go out. This took a few times and it finally stayed on. I'm not sure what causes this?
So I hooked the meter up to the TP/TH terminal and ground and was getting 550 MV with switch off and with switch to on it would read 275 MV (with glass off). Put glass on the front and Thermopile readings were 610 MV in off position and on it read 285 MV and in thermostat position read 290 MV.
Are these readings acceptable? I cleaned the TC and thermopile with emery paper and the readings didn't change much. The unit is working now in both the on manual position and the thermostat but I'm not sure for how long. The last time it went out was about 1/2 hr after lighting unit. Thanks for any input from the experts.
I was thinking on just buying a new thermopile to have on hand in case you say that is what it needs, and I will put it in, but just not sure. Thanks

paul

Those voltages for the T-Pile are acceptable. The reason for the voltage drop is the resistance when the voltage travels from the T-Pile, where it is generated by the pilot flame, through the switch wires and back to the valve.
If it is going out after running for a period of time I would look at the venting. You can check to see if it is a venting issue by slightly opening the glass and observing it for a period of time.

 

[PaulRV6]

Thanks Lennox65. When you say a venting issue are you thinking to check if it is maybe obstructed in any way? Is there a mechanism built-in that would shut the stove off if blocked? I don't know of any switches that would do this? Thanks for the help.

paul

 

[Lennox65]

Thanks Lennox65. When you say a venting issue are you thinking to check if it is maybe obstructed in any way? Is there a mechanism built-in that would shut the stove off if blocked? I don't know of any switches that would do this? Thanks for the help.

paul

Not a switch, but either an obstruction in the venting or a break in the inner pipe causing exhaust to be recirculated with the combustion air.

 

[PaulRV6]

Thank you Lennox. I'm a little slow on this so can you explain in more detail how this could cause the stove to cut out? Are you saying that if there is a break in the inner pipe that the incoming air is blowing back into the exhaust and blowing out the flame? Thanks for helping me understand.

 

[Lennox65]

Thank you Lennox. I'm a little slow on this so can you explain in more detail how this could cause the stove to cut out? Are you saying that if there is a break in the inner pipe that the incoming air is blowing back into the exhaust and blowing out the flame? Thanks for helping me understand.

No, not blowing out the flame. If the exhaust gets drawn into the combustion air then the air to fuel ratio is changed because the exhaust does not contain clean oxygen that the fuel needs to continue to burn properly.

 

[PaulRV6]

So the fireplace has been on for about 5 days and yesterday out of the blue it just went out. This is when the flame was on full it just went out. It was on thermostat setting but it wasn't from reaching temp setting bc the pilot also went out. No high winds or anything. I checked the vent and all is good there. How can I tell if this is a direct vent that takes combustion air from the outside??
It is a straight shot thru the wall with a fancy screened vent cover from VC. I will get a photo of the outside vent. Any thoughts? Thank you

 

[PaulRV6]

Here is a shot of the vent on the outside wall.