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Old 10-05-2007, 02:04 PM   #1
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Vaillant boiler, burner doesn't ignite


Hi, I have a Vaillant Turbo Max combi boiler and if you turn on the heating or a hot water tap, the green light in the control panel flashes so it knows there is demand but the burner ignites but then goes out straight away. I have to keep pressing the ignite button and even then it takes several attempts before the burner stays lit. Has anyone got any ideas? Thanks all, Davey

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Old 10-09-2007, 12:30 PM   #2
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Vaillant boiler, burner doesn't ignite


Hi Davey

I am in the US and am not really familiar with your unit, and haven't found a online manual. However it would sound to me like it is shutting down because of a flame proving sensor or similar. If it has a hot surface igniter (the kind that glows brightly before the gas turns on to light the flame) it may sense threw it other units could use a thermocouple to make sure the flame is lit. Most likely they sense the flame and if not proven they shut the unit back down for safety.

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Old 10-10-2007, 12:44 PM   #3
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Vaillant boiler, burner doesn't ignite


Hi Matt,

thanks for the info, sounds pretty good to me. I think a thermo coupling is relatively cheap so I might just fit one and see how it goes.

Thanks, Davey
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Old 10-18-2007, 01:35 PM   #4
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Vaillant boiler, burner doesn't ignite


You can't replace an igniter with a thermocouple because there's no standing pilot.
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Old 10-18-2007, 05:24 PM   #5
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Vaillant boiler, burner doesn't ignite


Hi Harryo
I didn't suggest to change it from one to the other:confused: I said I didn't know what he had not being familiar with the unit and wasn't yet successfully locating information on it. I described the example of a how a igniter could fail possibly causing his complaint but brought up other units could use a thermal couple. I don't know if he also miss understood me too:o but you are right without major modifications you cannot go from one to the other. I didn't assume what type of system he had.

Example of why I did not assume a system uses a igniter
(I worked on a hot-jet type parts washer burner that had 2 separate thermal couples, one for the standing pilot light and one for the burner proving both were 750 mv thermal couples but the unit still had a 24 volt supply for a electronic relay timer to activate the burner from the pilot thermal couple power after it would then default the burner thermal couple to stay activated. Ether thermal couple could prevent the burner from working even with the pilot lit the voltage could drop to low for the burner to sty on if the pilot thermal couple was week.


If you know the Vaillant boiler system at all then hopefully can help Davey out with his problem or maybe post some info of its system..
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Old 11-06-2007, 11:49 AM   #6
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Vaillant boiler, burner doesn't ignite


I have some experience with a variety of domestic boilers including Vaillant. There are 3 possibilities for your problem.
1. The "draft" sensor on the boiler fresh air inlet on the flue tube has failed. This basically cjhcks that the temperature of air flowing into the flue tube from the outside (or room it is housed in) is less than the combusted gases going up the flue. If it isn't then the gas supply is stopped & the boiler will fail to light off. These sensors are temperature sensitive diodes covered in black heatshrink. The purpose is to stop the boiler if the flue is blocked, i.e. it checks that there is relatively negative air pressure in the flue in order to allow the flue gas to escape up the chimney...as it should.

2. If there is too much "draft", then the light off of the gas burner in the boiler is unstable, the ionising detector (2 small rods which are in the burner flame area connected to 90 to 100 Volts ac) senses no flame & immediatley stops the gas to the boiler burner. To check how strong the "Draft" is use a standard cigarette lighter. Turn off the gas supply to your boiler first (just in case you have an leak you do not know about), then light your lighter & move the flame to the air distribution plate below the boiler burner. If the flame is "sucked off" the end of the lighter then there is too much draft.

Reducing the draft is not a simple task & should not be attempted by novices.

3. You can remove the "flame sensor" if it is the "rod type" & shine them up with a piece of Hemery Cloth (sand paper for metal) or a metal pan scourer or wire wool. If they are blackened they do not pass enough signal for the flame sensing circuit.

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