Gas Hydronic Heater Ignition Problems. SOS


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Old 06-11-12, 05:20 PM
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Gas Hydronic Heater Ignition Problems. SOS

Hopefully someone out there can help me as this is doing my head in. I have Vulcun 30 Propane Hydronic Heater unit which is playing up and have tried to fix it without sucess with my limited knowledge. The problem arises when the pilot is lit and then when the main burner ignites there is a click sound after 15-30 seconds and the main burner goes out along with the pilot. I have installed a new thermocouple, cleaned pilot feed tube and jets, also cleaned out the main burner which has an even flame when going. Ocassionally the main buner will stay on after I have left the pilot run for a couple of hours, however it always shuts down within a few hours after this happens. I don't know wether the pilot light is blown out when the main burner re-ignites on the second,third etc occasion or what. I have had the Gas line pressure checked and that appears OK.
 
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Old 06-11-12, 07:31 PM
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Not being familiar with that equipment, I'm going to have to venture a guess & say your pilot orifice may be partially clogged. When the main burner comes on, it pulls enough gas from the pilot to cause the pilot size to decrease & allow the pilot sensor to cool thus causing the pilot to shut down.
 
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Old 06-11-12, 08:23 PM
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Like Grady, I am not familiar with the equipment but this:
...when the main burner ignites there is a click sound after 15-30 seconds and the main burner goes out along with the pilot.
sounds like perhaps there is a flame rod sensor that is looking for a signal through the main flame and when it doesn't it shuts the main gas valve. That wouldn't explain why the pilot also goes out but it could be a combination of problems.

Does the gas burner have a small diameter metal rod in a ceramic insulator on the far side from the pilot burner? Pictures would help.
 
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Old 06-12-12, 03:08 AM
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Thanks Guys taking an interest in my problem. Grady, I thought the same so I have thoughly checked the pilot gas feed tube, blown compressed air through it, also checked the feed tube jet for any debis, but that seems fine. I have thought of opening the jet hole size to keep the flame in contact with the thermocouple. Furd, there is no flame rod sensor on this unit, only thermocouple and pilot. I cannot provide photos as I am currently away from where the heater resides. As for photos I can provide these over next weekend so sorry for the delay. Is there a specific detail you would like to see in the photo to pinpoint the problem?
 
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Old 06-12-12, 06:31 AM
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I'm supposing that you have a standing pilot which should be staying lit all the time whether the burner is lit or not --- is that right?

That's the only system that would have a thermocouple.

Since you've replaced the thermocouple and cleaned the pilot orifice, the remaining likely problem is a gas valve with a failed magnet. That would require replacing the electric gas valve, which is not a suitable DIY job.

Call a competent repairman to confirm the diagnosis and probably replace the gas valve.
 
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Old 06-12-12, 09:21 AM
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Since you have verified there is no flame rod we can dismiss that as being a problem, it was a long shot anyway.

I would like to see pictures of the gas piping inside the cabinet. I want to see all the valves and devices connected to that piping. Seattle Pioneer may be correct but I think that you have a problem with limit switch somewhere. Or, it could be a failure in the control board.

The action you describe, pilot stays on indefinitely unless the main flame comes on and then all shuts down 15-30 seconds later does not sound right unless you have a Power Pile system. Is your thermocouple a slender rod, about 3/16 of an inch in diameter with a single screw connection to the gas valve or is it more like 1/2 inch to 5/8 inch in diameter with two wire connections to the gas valve?
 
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Old 06-13-12, 04:32 AM
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Furd, thermocouple is around Dia 3/16 at the sensor with a similar Dia copper line for it running to the valve unit. If the pilot flame drops when the main burner ignites then the thermocouple might not sense the flame and hence shut the main burner off, could this be a problem?

SeattlePioneer, yes it has a standing pilot light lit all the time with a thermocouple. You mention a failed magnet in the gas valve. Is this part not serviceable.
 
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Old 06-13-12, 10:08 AM
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That certainly sounds like a regular thermocouple and not a PowerPile system. With a PowerPile there is no external electrical requirement for the gas valve, it generates its own power. Sometimes the PowerPile can put out enough power to hold the pilot valve open but not enough power to operate the main valve. When this is the case the drop in voltage when the main valve tries to open causes the pilot valve to also close. But this does not appear to be the case in this installation.

What IS possible is that a stuck pressure regulator, either external to the gas valve assembly, or an internal part of the gas valve, could be sticking. It would allow enough gas for the pilot only but when the main valve opened the gas flow would drop the pressure to below that necessary to maintain the pilot. This is why pictures are needed to ascertain exactly what you have in the "gas train" piping. More pictures are always better than fewer and they need to be well lit and in focus.
 
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Old 06-19-12, 04:18 AM
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See attached photos showing the pilot outlet, thermocouple and lighter along with valve unit.
 
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Old 07-03-12, 04:02 AM
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Still waiting for some feedback anybody
 
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Old 07-03-12, 03:45 PM
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There is indeed a flame sensor rod. The pilot impinges on it when lit. The flame rod is the porcelain, metal tipped rod in front of the pilot burner. Use some very fine sandpaper or a piece of Scotch Brite to clean the metal rod end. It may or may not help but it's worth a try.
 
 

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