Adjusting the Offset

Alan (California Radiant) Forbes

@GroundUp once said:

"If you adjusted the low fire screw far enough to raise the high fire reading by .7%, you've created bigger problems."

I've always heard that you can damage the valve if you adjust the offset too much. Can anyone elaborate?

mattmia2

as i've said before my bet is that it isn't actually damaged but the settings are so far off that it would be very difficult to get them close enough to correct to get the boiler to fire without putting the valve in a test jig with instrumentation.

GroundUp

I have heard this too, but never actually seen it in person. The reference above was more about the fact that the low fire would have been so out of whack by adjusting it far enough to move the high fire reading that far, just for clarification. I have had a handful of 150-199k Nobles where the high fire were still really lean even after turning the bias screw out to the point that it wasn't making changes anymore, and admittedly out of frustration on a couple just kept turning in hopes it'd fatten up. One of those a few weeks later had symptoms of a bad gas valve so I thought I'd finally wrecked one, but the new one had the same symptoms. Turned out to be a bunch of loose foam insulation like material in the burner, which I can only assume came from the ongoing construction outside the building. Cleaned the burner out and put the original gas valve back in, still lean (as was the new one) but the rep assured me that it was within spec…

HVACNUT

I think I've only made low fire adjustments three times in my life. If the CO is good, and CO2 is close, I'll leave it alone. Because I know that it'll effect the high fire that I just spent a half hour getting DOBA. When I go back the following year, its all good.

GGross

It depends on the valve! A few years ago I took apart a gas valve for a triangle tube instinct boiler. This was during a time when we HAD to adjust that screw on LP gas due to a programming issue. On that particular valve the screw was pushing against a little air pillow right behind it, I imagine the instructions to wait a minute had to do with allowing that air pillow to settle. You could very likely damage that air pillow by playing with the screw too much, however it seemed to me like it would be a little unlikely.

GroundUp

https://forum.heatinghelp.com/discussion/comment/1889789#Comment_1889789

You must not be installing Lochinvar Nobles (the original context this post is referring to), huh? Like 9/10 are not even close without low fire adjustment