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Adjusting offset

metrosilo Member Posts: 33
Hi. I was recently performing a maintenance on at AO Smith BTH400 Cyclone. I don’t normally do a combustion but I decided to do one cause I suspected it wasn’t running right. 
As suspected, I found my O2 very low at 1.9. Gas pressures are within range. No more than 1.5” drop. I used the regular gas adjustment to adjust my o2 up to 5. 
There is an offset adjustment on this gas valve and I can’t figure out how to use it. Instruction don’t really explain it well. 
Has anyone have any experience with these gas valves? 
More specifically, using the offset adjustment?


  • HomerJSmith
    HomerJSmith Member Posts: 2,440
    Follow the manufacturer instructions for doing an offset on the gas valve. You need a recently calibrated CO meter to properly make the adjustment.
  • Zman
    Zman Member Posts: 7,569
    The offset is the difference in gas flow between high and low fire. If you set the high fire and the low fire specs are out of range, follow the manufactures instructions and adjust the offset. Be very careful to count your turns, it is easy to get lost and make a mess.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein