Noticing build up around chimney cap

[KG19]

This morning I went out and took a peek at my chimney and noticed what looks like a lump of creosote up by the chimney cap. It looks a bit worrying to me. But it’s also confusing because I’ve been burning quite hot, in fact almost too hot on occasions. I posted about a month back about overdraft on my Alderlea T6, then had a damper installed and also covered the boost air hole. These steps helped a lot to where I have a more controlled burn. I don’t use the damper often anymore since covering the boost air, and typically run with flue temps (on probe thermometer) in the 600-650 F range and STT usually around 600-700. I get good secondary combustion and am using 3 year seasoned wood, mostly ash.

I hadn’t noticed this until today, and I do typically take a peek at my chimney when burning every once in a while to monitor smoke. I usually have very little to no noticeable smoke except for a few minutes on reloads. And like I said I hadn’t noticed any of this creosote looking substance until today.

Something else to note is that we’ve had a cold snap here the past few days. The highs have been in the single digits with overnight lows below zero. Wind chills down to -25 F. Could that be maybe causing this condensation just around the cap? Or do I assume that my flue is getting build up and I should inspect/sweep? I’ve only been burning for about 1.5 months consistently with a brand new insulated liner and brand new Alderlea T6.

I’ve attached pics but it’s hard to get a good view with my camera due to the height of the chimney. In person it looks more noticeable. The screen itself seems pretty clear but it seems to have “build up” around the bottom edge/crown of the chimney itself. Almost like ice build up but it’s black. It seems to be really only on one side of the chimney.

 

[begreen]

It's not uncommon for creosote to condense on the underside of the slab of a big cold lid. The tall brick chimney can also be cooling down the flue gases below 250º. If so, they will start to condense. It wouldn't hurt to sweep as a check to see how things are looking.

 

[NickW]

I'd go up when it can be safely done, do an inspection and clean as necessary. When my screen starts to get a little buildup I pull it, clean it and the top 2 feet of my liner that sticks out of the masonry. Everything else is always fine for me.

 

[begreen]

KG19, is there an insulated 6" stainless liner in the chimney?

 

[stoveliker]

Yes:

I’ve only been burning for about 1.5 months consistently with a brand new insulated liner and brand new Alderlea T6.