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Buderus g234 problem

Bob Bona_4
Bob Bona_4 Member Posts: 2,083
Good morning wallies. I'm having a problem with a G234/64. Call came in last night for sooting, gas co found 3300 ppm in the vent. I brushed and vac'd the boiler out -fluffy soot, almost plugged. Pretty sure the problem was clogged burner tubes from sheetrock dust ingestion..cuz they were clogged!

Start unit, flame is looking blue off the burners, then the gas valve starts to cut off after 15-20 seconds run time and restart. It's like it's failing to prove flame and keeps restarting, even though the flame is on. Pulled the burner rack again, rechecked pilot assy, blew through tube and orfice, still going on-off. After about 4-5 cycles, the roll out switch went.

Temporarily jumpered RO switch and checked for steady voltage at the module, and looks like power drops at the top two term's (sorry, can't remember what the designations were)when the gas valve does it's cut in/out.

Stumped. The cust has no heat or HW as of now. TIA!!!


  • ScottMP
    ScottMP Member Posts: 5,884

    Check the flame rod, clean it good, also check for a good ground.

    When you cleaned it did you brush out the whole block ? We had to use simple greeen once and flush the whole thing with a hose.


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  • J.C.A._3
    J.C.A._3 Member Posts: 2,981

    Like Scott said...check the flame rod AND make sure the connection is good all the way. I had a similar one and the blue wire going down to the rod was broken right at the base of the rod. I had to wiggle it to make the connection break while I had it removed...but it WAS cutting out when heated by the main fire.

    I hope this is a natural gas unit....trying to get the pilot assembly for an LP unit on short notice proved to be a tough ride. Chris
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    could you guys give me a call?

    I'm heading out to the job again, and I'll follow your suggestions..203-223-1262 cell Thanks!
  • J.C.A._3
    J.C.A._3 Member Posts: 2,981

    I know our conversation went over the troubles that could cause the problems...but I Hope I helped.

    Brotherhood...what's a better way to TEACH and LEARN? Chris
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    still apart

    Thanks you guys for the calls and direction. I spent Saturday from 9 30 until 4 30 washing the thing out, and then cleaning up the mess from the wash-the boiler is in a tiny finished, white stone tiled closet off a small bathroom..IN AN ATTIC THREE STORIES UP :) My brushing out the night before apparently did not do enough (I thought I had sent the brush all the way through), and I underestimated the amount of soot build up especially on the bottom part of the HX. On the burner tray I found the pilot porcelan slightly chipped and the ignition wire melted right at the porcelan connection-not enough to see conductor, but enough to see a blob of molten wire insulation that dribbled down about 3/4" from that point.

    JCA and Ken from Seattle both told me that could cause a faulty grounding signal to the ignition module. A few minutes ago I had my wholesaler next day air a roll out switch and a new pilot assy.

    I have a dumb question: Is the Buderus roll out switch a simple contact, or is there a resistance value that must be maintained to have the module operate correctly? In other words, can jumping the RO give the control erroneous readings?

    Will give updates as they come. Thanks again!
This discussion has been closed.