Vermont Castings Vent free Stardance UVS27 will not light main burner

[mbell]

Hello. I have a freestanding Vermont Castings vent free propane Stardance UVS27 that we bought second hand. I don't know the age, but I do see 1997 in the ANSI number of Z21.11.2a-1997, which may reference the age? The problem is that the main burner will not ignite. The pilot light will light quickly and stay burning after holding the control knob in for approx 20-30 seconds. The pilot stays lit after releasing the control knob. The pilot flame is strong and blue and nicely surrounds the end of the thermopile. When I turn the control knob to the full light position, I hear a click or thunk in the valve area and the pilot light goes out. The main burner never lights. I have done the following troubleshooting:
- gas company verified proper gas line pressure to the stove and leak test
- I cleaned the thermopile all around with fine grit emery cloth
- I cleaned the pilot light opening and thermopile with q-tips using isopropyl alcohol
- vacuumed the inside of the firebox and burner area
- I tested the voltage from the thermopile to the gas valve terminals and it was at 750 mV while the pilot was burning
I do not know what steps to take next. Any suggestions or help would be greatly appreciated. Thanks!

 

[Lennox65]

Hello. I have a freestanding Vermont Castings vent free propane Stardance UVS27 that we bought second hand. I don't know the age, but I do see 1997 in the ANSI number of Z21.11.2a-1997, which may reference the age? The problem is that the main burner will not ignite. The pilot light will light quickly and stay burning after holding the control knob in for approx 20-30 seconds. The pilot stays lit after releasing the control knob. The pilot flame is strong and blue and nicely surrounds the end of the thermopile. When I turn the control knob to the full light position, I hear a click or thunk in the valve area and the pilot light goes out. The main burner never lights. I have done the following troubleshooting:
- gas company verified proper gas line pressure to the stove and leak test
- I cleaned the thermopile all around with fine grit emery cloth
- I cleaned the pilot light opening and thermopile with q-tips using isopropyl alcohol
- vacuumed the inside of the firebox and burner area
- I tested the voltage from the thermopile to the gas valve terminals and it was at 750 mV while the pilot was burning
I do not know what steps to take next. Any suggestions or help would be greatly appreciated. Thanks!

The two times that I have encountered a similar problem, once the supply piping was undersized and the other time there was an obstruction of pipe dope (thread sealant) in the supply line. Have you checked the main burner orifice and piping for obstructions?

 

[FireSafe]

Hello. I have a freestanding Vermont Castings vent free propane Stardance UVS27 that we bought second hand. I don't know the age, but I do see 1997 in the ANSI number of Z21.11.2a-1997, which may reference the age? The problem is that the main burner will not ignite. The pilot light will light quickly and stay burning after holding the control knob in for approx 20-30 seconds. The pilot stays lit after releasing the control knob. The pilot flame is strong and blue and nicely surrounds the end of the thermopile. When I turn the control knob to the full light position, I hear a click or thunk in the valve area and the pilot light goes out. The main burner never lights. I have done the following troubleshooting:
- gas company verified proper gas line pressure to the stove and leak test
- I cleaned the thermopile all around with fine grit emery cloth
- I cleaned the pilot light opening and thermopile with q-tips using isopropyl alcohol
- vacuumed the inside of the firebox and burner area
- I tested the voltage from the thermopile to the gas valve terminals and it was at 750 mV while the pilot was burning
I do not know what steps to take next. Any suggestions or help would be greatly appreciated. Thanks!

Obviously your thermocouple (if you have one) is working fine and sending proper voltage since your pilot remains lit.
Your thermopile is sending proper voltage.
Gas company says proper supply pressure.

Have you checked to see that your the 2 leads from your on/off control (remote receiver, thermostat, switch, or whatever device you use to turn the main burner on/off) are properly connected to the valve? You can do a quick test to see if there is a problem with the switch device by using a wire to touch (jumper) both connection terminals, if the main burner comes on then the problem is with your control switch device.

If the jumper doesn't cause the main burner to come on, then the problem is with your valve (you said it makes a clunking sound) and will need to be replaced.

 

[DAKSY]

Look at the back side of the pilot tube.
There is a small hole that is the Oxygen Depletion Sensor (ODS).
Clear it of any dust or pet dander with a can of compressed air.
If that ODS gets blocked, your burner will not ignite.

 

[bando5304]

Did this ever get figured out? I have a Vermont Castings LHEC30 that has the same exact problem. Pilot lights fine but when I turn the knob to on, there is an audible clunk sound and the pilot goes out. I've replaced the thermocouple and thermopile. Pilot flame is good. The unit worked fine last year.