Viessmann Chassis Burner Issues

AirborneTrav

I'm having an issue at a very good customers house, and I'm kind of at a loss. The boilers are 2 gas fired Viessmann Vitollas with Vitoflame 200's (VGA 50) on them. One burner has been having issues for a while. Cleaned and tuned them a couple of weeks ago, replacing all three electrodes and gapping them correctly. Did combustion tests and everything checked out. He had a fault on boiler number one about a day later. I went there again, tried to get it to fault out, failed, and after trying about 25 times decided to order a new burner control, sub base and transformer. I also switched the burner heads, to see if the problem followed the burner or stayed with the boiler. He reported a fault at boiler number two (now with the burner head that had been faulting out on boiler number one.)
I came here this morning, changed the 3 parts, and with the new transformer seemed to be faulting out more often. I am seeing late ignition, but not every single time. I put the old transformer back on, and it still faults out once in a while, just not every time. Most of the time ignition is smooth, occurring just after the click of the gas valve. Sometimes I see a delay, then a boom when it finally ignites, and less frequently it doesn't ignite at all. I checked the electrodes again, and cleaned the spot on the turbulator where it makes spark, and also swapped the ignition cables on the burners to take that possibility out of the equation. I am also certain its not anything in the gas train because the problem followed the burner. The pressure at both manifolds is within .1" WC of name plate.
Can anyone think of anything else that can be causing this? I really have run out of ideas. Any input would be greatly appreciated. I am almost at the point of quoting a Riello for him. I didn't install these and the problem has long preceded me, but I would like to do right by him and try everything I can within reason before changing the burner out. - Thanks, Travis

Robert O'Brien

Microamps?

http://www.bgtherm.com/products/heating/cauldrons/water_heating/d/Installation/VITOFLAME 200 GAS GB.pdf

AirborneTrav

Sorry Robert, could you elaborate?

Robert O'Brien

What microamp reading are you getting with burner running? What fault code?

AirborneTrav

Got ya, don't remember exactly, but it was within the accepted range. Also, when the fault occurs I am getting no ignition whatsoever, so I had ruled out a flame sense issue.

GW

What do you mean by burner head? The entire burner assembly or literally the head? Can you be more specific? The whole chassis that sits 90 degrees when you hang it for service?

So the gas valve flipped boilers or stayed at its original boiler?

AirborneTrav

When I say I switched the heads, I broke the union on the pipe coming from the gas valve, undid the quarter turn Allen bolts and removed the assembly from the mounting on the boiler (the piece you would normally hang,) and put that on the other burner. The gas train stayed where it was, so now the burner that had been going into fault on boiler one was now mounted on boiler two. It continued going into fault on boiler two, leading me to deduce that it was not a problem with the gas train.

Robert O'Brien

Failure to light means one of the 3 necessities for combustion is missing. Fuel,air,ignition.

aircooled81

Is the ignitor clicking, or providing a constant arc?
I had a few peerless that taught me the ignition on the ignitor was a hot constant arc, not a clicking. One had a bad ignitor that refused to arc at any gap. The other had a bad board that would not output the correct voltage to provide the constant arc, just a constant click.
Basically, the chambers would fill with gas, then boom, delayed ignition, or no ignition at all and fault.

BobC

Back when I had a oil burner I was working down cellar I was working on the bench when i heard the burner kick in, there was a noticeable delay and then the draft damper shot across the cellar.

I had heard what sounded like delayed ignition for a couple of days but that made me investigate further. The arc I was getting out of the ignition transformer looked very weak. I ordered a new transformer that night and had it in hand two days later - problem solved.

Make sure you verify it's bad before you order a new one.

Bob

GW

That's not good, new trans was worse? So when it doesn't fire, can you tell what isn't happening? I has a chassis once get me real good, loose wire plug connection, I have since forgotten which wire it was

AirborneTrav

GW, the new transformer seemed to have made the issue worse. I had trouble ever getting it to fault out before the new transformer- it seemingly would only happen once in a while. When I put the new transformer on, it started to happen every 3 or 4 times. Don't think its the connection- I have checked and rechecked every one.

GW

Yes that's a bummer, if you have the energy you could start swapping parts between the two burners. You need to check the plug connectors behind the flip-down assembly