Boiler stack performance vs. relative humidity & dew point

[gondolier88]

This is very common, on still days with low atmospheric pressure and high humidity it is difficult/impossible to get the fire to draw on natural draft.

Lighting a boiler every day for years you get to notice what makes a difference, and days like those you mention were always a killer. High on fuel, low on steam, and usually sweating buckets for the pleasure. It is something I've experienced on numerous boiler types and is no extraordinary phenomenon, just another elemental facet to using steam power.

Once running, especially if using puffing exhaust, the problem usually disappears, but woe betide if you come to a stop and forget to open dampers up.....

Greg

[Lopez Mike]

I burn wood with a fairly tall stack and I have more draft than I can use almost of the time.

To paraphrase Willy Nelson in The Electric Horseman, "It can suck the chrome off of a hitch ball"

[RGSP]

This is very common, on still days with low atmospheric pressure and high humidity it is difficult/impossible to get the fire to draw on natural draft.

Lighting a boiler every day for years you get to notice what makes a difference, and days like those you mention were always a killer. High on fuel, low on steam, and usually sweating buckets for the pleasure. It is something I've experienced on numerous boiler types and is no extraordinary phenomenon, just another elemental facet to using steam power.

Once running, especially if using puffing exhaust, the problem usually disappears, but woe betide if you come to a stop and forget to open dampers up.....

Greg

When someone like Greg says this happens, it's pointless to try and claim it doesn't. I wonder whether it's to do with the temperature inversions we often get on autumn mornings in England, which are often associated with very high RH or mist at ground level and a few feet up. It wouldn't surprise me if they were rarer in other parts of the world, though for all I know they could be commoner.

[DetroiTug]

There is something to this.

Remembering back when I used to work outside more. We would occasionally build fires to get rid of underbrush. An old timer told me that when smoke rises high it means fair weather is present for the interim, and when smoke hangs on the ground, it means rain is headed in. And it's true more often than not.

A few more of those although unrelated:

If the sun comes out when it is raining, it will typically rain at the same time the following day.

If it thunders in February. it will snow in may. (Northern USA)

I exhaust up the stack so none of this applies

-Ron

[Lopez Mike]

You exhaust up the stack? That sound like something that happens around election time!