Black glass ONLY after all night fire

[MasonsDad]

I have a heat n glow Northstar ZC that I installed earlier this year. My fires during the day have gotten a lot better. Able to get stove up to temp and let it cruise at or near 500deg. I often increase the air, when I am home, once I get towards the end of the burn cycle. An hour before bedding down I load the fireplace with about 5 splits of good dry (split and stacked 5 years ago 16-19%) mixed hardwoods and leave the air open until it gets going. I then turn it down as I normally do until the secondaries are going strong. This usually means choking off all the air or very close to all of the air same as I do during the day, but when I get up in the morning I have Black glass. I always have enough hot coals for relight but without being able to increase the combustion air at the end of the burn cycle the glass just turns black and if I increase the air before going to bed I am afraid of an overfire while I am sleeping. Is this common? Suggestions?

 

[firefighterjake]

I suspect you're choking it down a wee bit too much . . . leave the air control open just a dite more than what you usually close it at and see if that doesn't improve the situation.

 

[Jags]

Yep - Jake is on it. Just a pinch more open on the primary and you will probably have a nicely cruising stove and no black glass.

 

[MasonsDad]

I suspect you're choking it down a wee bit too much . . . leave the air control open just a dite more than what you usually close it at and see if that doesn't improve the situation.

Overfiring while I sleep not a problem? I have opened it up a bit more than usual and come back an hour later to a much larger / hotter fire than what it was cruising at. Never an overfire just a hotter fire

 

[Jags]

Overfiring while I sleep not a problem? I have opened it up a bit more than usual and come back an hour later to a much larger / hotter fire than what it was cruising at. Never an overfire just a hotter fire

Without a doubt it will be hotter than when you run it and get the glass smoked up. That is the point...the smoked glass tells us that you are not running it hot enough at night.

 

[Wood Duck]

Try leaving the air open a little more during a daytime burn, to simulate what would happen overnight. After a few daytime tries you'll figure out how to set the air and neither overfire nor get black glass. Or at least you'll figure out if it is possible to avoid overfire while avoiding blackened glass too. I bet it is possible.

 

[MasonsDad]

Overfiring while I sleep not a problem? I have opened it up a bit more than usual and come back an hour later to a much larger / hotter fire than what it was cruising at. Never an overfire just a hotter fire

Thank You. Makes perfect since. Sometimes it just takes somebody else telling you to make it clear. I guess I am always afraid of over firing at night or worse and error on the side of caution, but as you say it is not hot enough or the glass would not be dirty.

 

[Jags]

As wood duck was getting at - if it makes you more comfortable do a couple of test runs during the weekend or when time allows. You will see first hand what the stove is gonna react like.

 

[David.Ervin]

I've got the same stove, and the advice you're getting is spot on. I usually run it about 1/3 open for overnight burns, and the glass stays fairly clean. I've found that the airwash in this unit isn't all that great, so I'll always get at least two spots of soot build up on the top of each door glass, regardless of how hot it is, and it'll smoke over entirely if I close it down too far.

 

[Shari]

While agreeing with all of the above it probably wouldn't hurt to check your chimney - black glass means smoldering which can lead to build up inside your chimney even with seasoned wood.

 

[MasonsDad]

thanks for all of the replies. I will open the air up a little more as suggested. I did check the chimney this past weekend and it has a light layer of hard creosote in it but I do not think anything to be concerned about at this time. I will continue to monitor it.

 

[branchburner]

This usually means choking off all the air or very close to all of the air same as I do during the day, but when I get up in the morning I have Black glass.

Funny reading this today, as I woke up to see blackened glass for the first time in awhile. Why? Set the air at about 5% open overnight instead of my usual 10-15%. So the exact air setting will be different for every stove, but the principle is the same.

 

[begreen]

Thank You. Makes perfect since. Sometimes it just takes somebody else telling you to make it clear. I guess I am always afraid of over firing at night or worse and error on the side of caution, but as you say it is not hot enough or the glass would not be dirty.

To build confidence, experiment more during the weekend when you can watch the fireplace through complete burn cycles throughout the day.