Buderus GB 142 ignition issue (6A)

Dave19

New customer has a GB142 with 6A code. Previous company replaced gas valve and venturi. If I put my hand over venturi, the unit will light. Hand off.....and no ignition. Gas pressures are all within range. Inlet is 11wg, and outlet is -.02wg. Gaskets and covers are all tight. Why is this thing blowing itself out? I can sit there with my hand on the venturi, get it to light and run....remove my hand and watch the flame lift right off burner plate and go out. Anybody seen this before?

HVACNUT

The new gas valve needs to be adjusted by the throttle screw, while you have your analyzer going. Adjust to Buderus specs for CO2 and O2.
Decreasing the air with your hand means an improper air/fuel ratio.

Dave19

I set burner pressure to what the manual called for...it was about -.02 to -.03. That's how it says to correct air ratio in the manual. Is there another way? Throttle screw?

HVACNUT

They're calling it the set screw, Fig. 60.
Don't adjust unless you have an analyzer.

lchmb

You can cover the intake to get it started, then adjust from there as needed..but like mentioned you must have an analyzer..

prplhz96

Hate to resurrect an old post, but can def use some help fellas. I have a customer with a Buderus GB. The unit had a faulty tach in the fan, was throwing 6c code. Replaced the fan, and serviced the heat exchanger. It was pretty nasty, def has not been cleaned in a few years. Besides throwing a daily 6c code the last month, no other issues. A reset was all that was needed to get the unit back up and running. So, I put the fan on today along with a new condensate tank, old one was cracked up top, and gave her a good cleaning and new gaskets. Unit won’t fire. Has fuel, and igniter is functional. If I cover the intake partially with my hand, she comes to life and runs beautiful. I put my dual port manometer on it, and incoming pressure is perfect, NG @ 6.8. When I set the differential, still same issue unless I cover the intake 50%. I turned up the gas pressure trying to get this to stay running, and with the adj screw maxed out(all the way in), she will run. I am at a loss here??? Thanks in advance for any help!!
-Jason

Dave19

In my case we ended up getting a Buderus rep out and the motor rpm was spinning too fast blowing out the flame. I can't say that's your issue also, because you say you replaced the fan, but I checked everything on that unit.....went thru all the troubleshooting in the book.....several phone calls to tech support....and even had other company techs look at it. Everyone scratching their heads and that's what ended up fixing the issue. Stupid question but did you fill condensate back up with water before start also? Ive done that before.

prplhz96

> @Dave19 said:
> In my case we ended up getting a Buderus rep out and the motor rpm was spinning too fast blowing out the flame. I can't say that's your issue also, because you say you replaced the fan, but I checked everything on that unit.....went thru all the troubleshooting in the book.....several phone calls to tech support....and even had other company techs look at it. Everyone scratching their heads and that's what ended up fixing the issue. Stupid question but did you fill condensate back up with water before start also? Ive done that before.

Yes, I filled it back up. I am going to replace the gaskets on the plenum inside the intake tube. They are def sucking some extra air in, and I guess I will see if that has an effect on the unit. Thanks for the reply man! Appreciate it

DZoro

What shape is the venturi in? Any chance for re- injestion of flue gas? What is your O2 and CO readings?