Vermont Castings pilot problem

[Vermont Mike]

Hello.

I have a 22 year old Vermont Castings Radiance Model 2600. The pilot light extinguished some time ago.

Button in, click on the piezo, pilot lights with strong flame through thermopile and thermocouple.
Hold for 3 minutes, pfft, pilot flame quits.

Haven’t checked voltages yet. From everything I’ve read on this informative forum it’s probably the thermocouple. I’ve cleaned, vacuumed and emeried the thermopile and surround.

If there are any suggestions I’d appreciate them.
Cheers, Mike

 

[DAKSY]

Take reading on the thermocouple (TC).
You will probably need an extra pair of hands to do this.
Get a multimeter & set it to VDC.
Unscrew the TC from the gas valve & put one of
your probes on the EXTREME end & the other one
somewhere on the Copper sheathing.
Light the pilot & hold the knob in.
Read the mV on the TC, which shouldn't be lower
than 28 mV.
If the reading is lower, replace it.

 

[wooduser]

http://www.fireplaces-rochester-ny.com/manuals/VERMONT CASTINGS/Gas Stoves/Radiance.pdf

Here is a link to the manual; for your fireplace. Page 30 has an illustration of what the pilot flame should look like.

Both the thermocouple on the left and the pilot generator of the right should be engulfed by a lobe of the pilot flame.

You want to examine the thermocouple lobe with particular care since that's the part that helps keep the pilot lit.

The pilot flame should be a sharp blue flame, like a small blowtorch. If it's a lazy flame like a candle flame has yellow tips or is failing to due a good job of engulfing the thermocouple, the pilot orifice is probably dirty and needs to be cleaned.

A dirty pilot burner is a much more common problem than a failed thermocouple, so checking that carefully is worthwhile, in my opinion.

But if you have a good pilot flame that is engulfing the thermocouple, then it's probably a bad thermocouple.


Measuring the thermocouple voltage output as suggested by Daksy is also worthwhile, since you could have a good thermocouple putting out proper voltage but a bad gas valve that isn't using that voltage properly to keep the pilot lit.

 

[Vermont Mike]

Thanks Daksy and wooduser.

I do have the manual and the flame is sharp blue and enveloping the lobes well.

I’m gonna do a more thorough cleaning then check the voltages. I’m away for a little bit so I’ll be back to you in a couple of weeks.

Thanks much. Cheers, Mike

 

[k0wtz]

Thanks Daksy and wooduser.

I do have the manual and the flame is sharp blue and enveloping the lobes well.

I’m gonna do a more thorough cleaning then check the voltages. I’m away for a little bit so I’ll be back to you in a couple of weeks.

Thanks much. Cheers, Mike

do your self a favor run down to the hardware store and get a thermocouple 5 bux or so. if you put it in and the thing doesn't light you will need a new gas valve. I just redid a Vermont castings stardance stove smaller but same theory of operation! let me know!

 

[Millbilly]

do your self a favor run down to the hardware store and get a thermocouple 5 bux or so. if you put it in and the thing doesn't light you will need a new gas valve. I just redid a Vermont castings stardance stove smaller but same theory of operation! let me know!

Not necessarily

 

[wooduser]

do your self a favor run down to the hardware store and get a thermocouple 5 bux or so. if you put it in and the thing doesn't light you will need a new gas valve. I just redid a Vermont castings stardance stove smaller but same theory of operation! let me know!

You wont find a thermocouple for this application in a hardware store. If you remove it and take it to a fireplace shop they may have one they'll sell you for $25 or so. Many shops wont sell parts to DIYers though.

 

[Millbilly]

If this is a bvent model you need to check the flu limit or spill switch. I would TEMPORARILY jump the flu switch. I can't stand servicemen that do this as a permanent fix as it is an important safety mechanism.

 

[wooduser]

This is a direct vented stove, quite different than a stove with a draft hood using B vent. No draft hood on a direct vented stove and thus no spill switch. So that at least is not a worry!

 

[Millbilly]

This is a direct vented stove, quite different than a stove with a draft hood using B vent. No draft hood on a direct vented stove and thus no spill switch. So that at least is not a worry!

By no means a VC expert here but are you sure that manual you linked is for his 22 year old radiance 2600? Also did the 2600 only come as a direct vent model? I know some other brands use one name but will offer bvent or direct vent models.

 

[k0wtz]

Some VC stoves could be ran direct vent or b-vent... Primarely the direct vent came into play for those that wanted to vent out the wall. Again in my readings a direct vent stove is supposed to be more efficient as it takes air from the outside for combustion I dont think it really makes much difference with stoves!

Our VC stove was made in the late 70s so B-Vent was all that was available in that time period. The more I read on free standing gas heating stoves efficiency is not their forte in operation. The only gas stove that might be efficient was one built by Lennox since sold to someone else a favorite ploy of manufactures to get out of their warrantees!

 

[Vermont Mike]

Thanks all. It’s a B-Vent Radiance 2600. The manual suggested above seems to have a different thermopile/thermocouple spark set-up. Here’s a picture.

I’m gonna check voltages later. I’m not sure what the flu limit or spill switch is.

 

[Vermont Mike]

 

[Vermont Mike]

I disconnected the center (TH/TP) wire, lit the pilot and measured 25mv initially climbing to 60 mv as the thermopile heated.

So, is the thermopile ok? So the problem may be the gas valve?

Cheers, Mike

 

[wooduser]

View attachment 236093
I disconnected the center (TH/TP) wire, lit the pilot and measured 25mv initially climbing to 60 mv as the thermopile heated.

So, is the thermopile ok? So the problem may be the gas valve?

Cheers, Mike

Well I found the following reference to a B vented Vermont Castings Radiance 2600:

http://www.cozycabinstoveandfireplaceparts.com/cgi/display.cgi?item_num=2600-2603

Part #55 is listed as a spill switch, presumably checking for spillage from the draft hood. That kind of switch will typically shut off the pilot light if it opens ---and if you have a poor electrical connection, that's a good reason why the pilot wont stay lit, often enough.

The picture of the gas valve reveals that you have a thermopile system that powers a magnet to hold open the pilot burner gas valve and to open the main burner gas valve.

You have three connections on the gas valve: TH, TH/TP, and TP. TH/TP is the common or "ground" side of the circuit.

Voltage to the TP connection energizes the pilot burner magnet, to hold that open when you release the gas valve plunger, and that's probably in series with the spill switch.

So what you want to do is to measure the millivolts between TP and TH/TP after you've lit the pilot and it's had a chance to warm up.

My memory of what millivolts are needed to keep the pilot lit are hazy ----perhaps someone else can contribute that voltage.


You should be able to trace two wire connections from the pilot generator ----one to TH/TP and the other to TP.

You can see two wires forming a cable, one to TP and the other to TH. They should be going to a switch to turn on the main burner gas. Power from the TP connection turns on the main burner gas connection at TH if that switch is closed.

You should find a wire going to the spill switch attached to the wire going to TP from the thermopile.

If the spill switch opens, it shorts out the voltage going to TP and the pilot wont stay lit. There's a reasonable chance that a bad switch or bad wire is causing that wire to be grounded when it shouldn't be, causing your problem.

 

[Vermont Mike]

Ok. I found the spill switch. I shorted it at the disc and tried the pilot again. No joy.

I just ordered a Monessen 26D0566 thermopile just in case.

Still troubleshooting!

Cheers, Mike

 

[Vermont Mike]

Oh yeah. All the wiring appears good but I’ll do some continuity checks tomorrow.

Thanks everyone for all the help especially Wooduser and Daksy

 

[Millbilly]

TP readings WAY too low. You should be looking for 450mv plus with the switch off. Send a picture of the pilot assembly with it lit.

 

[Vermont Mike]

TP readings WAY too low. You should be looking for 450mv plus with the switch off. Send a picture of the pilot assembly with it lit.

Whoops. My error, Millbilly. It was 250 mv within seconds of lit pilot, climbing to 600mv after 40 seconds.

 

[wooduser]

Ok. I found the spill switch. I shorted it at the disc and tried the pilot again. No joy.

I just ordered a Monessen 26D0566 thermopile just in case.

Still troubleshooting!

Cheers, Mike

You want to temporarily disconnect the spill switch to test the pilot burner and gas valve. When it's shorted to ground it drains off the millivolts to ground and the pilot wont stay lit.

So try disconnecting it from the gas valve and try it again.

 

[Vermont Mike]

to test the pilot burner and gas valve. When it's shorted to ground it drains off the millivolts to ground and the pilot w

You want to temporarily disconnect the spill switch to test the pilot burner and gas valve. When it's shorted to ground it drains off the millivolts to ground and the pilot wont stay lit.

So try disconnecting it from the gas valve and try it again.
lit.

So try disconnecting it from the gas valve and try it again.

Thanks Wooduser. That makes sense. I’ll do exactly that and try it again. That’ll be tomorrow though.

I will get back to you. Thanks again. Hoping for flames by Christmas!

 

[Vermont Mike]

Oh yeah. All the wiring appears good but I’ll do some continuity checks tomorrow.

Thanks everyone for all the help especially Wooduser and Daksy

Here’s the lit pilot

 

[Vermont Mike]

Disconnected spill switch wiring. No joy. Same thing. Pilot lights ok. Strong blue flame on thermopile. Release pilot switch slowly. Flame extinguishes.

 

[wooduser]

Whoops. My error, Millbilly. It was 250 mv within seconds of lit pilot, climbing to 600mv after 40 seconds.

I saw your post that disconnecting the spill switch made no change.

The next thing to do would be to turn the main burner on switch to off, and measure the millivolts between TH/TP and TP and let us know what they are.

When you push against the gas valve to get the pilot gas to turn on, you are manually opening a safety valve that is usually held open by an electromagnet powered by voltage between TP and TH/TP. If sufficient voltage is present, the magnet should hold the gas valve open when you release it. (If the pilot goes out, the pilot valve snaps closed so that all the gas is off when there is no pilot light available to light the gas)


So what are the millivolts then?

If the pilot still doesn't stay lit, turn the main burner gas switch to on and do the same test again.

Withe the main burner gas control switched on, you are powering both the pilot burner gas valve magnet and powering the main burner gas valve, although the main burner gas will not turn on at that point.

What are the millivolts at that point?


Sorry if this seems drawn out. We're getting close to deciding what the problem is.

.

 

[Vermont Mike]

No, thanks for your time Wooduser.

Ok. I’m using the TOP and CENTER screw connection points(as shown in picture a few posts back) I get:

650 mv with pilot on and main burner switch OFF

250 mv with pilot on and main burner switch ON