Increasing flue height for better flow

[Oaktree]

Little background....... We’ve been having issues with our RSF Opel for quite some time. Typically I’ll run the stove up to ~450 degrees, then the coil starts to shut it down. The secondary burn is usually pretty short lived in our stove, less than 10 minutes. When the secondary burn quits the firebox just smolders and sporadically reignites, pretty violently at times.
So I reached out to RSF today and they suggested I extend my flue. From what I can tell Our flue is only a few feet short of their minimum required height. Can any of you give your opinions or personal experience on whether or not a few feet more of flue would be enough to change the way the stove operates?
Thanks!

 

[DAKSY]

"A few feet short..."
If the manual specifies a MINIMUM height, that
is what your chimney height should be.
Stoves are extensively tested for optimal function,
& if it performed well at the chimney height you have,
the manual would say so.
Why are you even questioning what the manufacturer says?

 

[Oaktree]

I question it because I’ve never been in the situation where I can say a few extra feet of flue made all the difference. Which is why I came here to ask my question. This site seems to be a wealth of knowledge on the subject. Surely someone here has been in my shoes before. Plus that few extra feet is going to cost quite a chunk of change and in the end I seriously have my doubts that it’ll make any difference. But I really hope it does.
And yes it was installed by a dealer.

 

[EatenByLimestone]

It will make a difference.

 

[Dmitry]

Little background....... We’ve been having issues with our RSF Opel for quite some time. Typically I’ll run the stove up to ~450 degrees, then the coil starts to shut it down. The secondary burn is usually pretty short lived in our stove, less than 10 minutes. When the secondary burn quits the firebox just smolders and sporadically reignites, pretty violently at times.
So I reached out to RSF today and they suggested I extend my flue. From what I can tell Our flue is only a few feet short of their minimum required height. Can any of you give your opinions or personal experience on whether or not a few feet more of flue would be enough to change the way the stove operates?
Thanks!

"Few feet short" lol. It's not a big difference when we talk about 30 ft flue, but a different story with 13 ft flue. My minimum is 15 feet if I'm short 3 then it 20% less than the minimum.
By the way, 450 top temp as a peak is very low in my opinion, ill run it around 600 before shutting down. If you have short flue try to run it hotter to induce more draft.

 

[Oaktree]

Thanks for your input and opinions. I really do appreciate that. I think I’ll bite the bullet and give it a shot. Hopefully it makes a difference.

 

[Dmitry]

Thanks for your input and opinions. I really do appreciate that. I think I’ll bite the bullet and give it a shot. Hopefully it makes a difference.

Does your glass get black and dirty? What is 450 temperature, where do you take it? How moist is the wood properly measured? I would check those things first.

 

[Oaktree]

It’s been pretty cold here lately so I’ve been running it hotter than normal. Right now there’s hardly any black anywhere on the glass. I’m not gonna lie I get some build up earlier in the season though. I bought a moisture meter a couple years ago and I split and measured a few pieces last fall. None were over 20%. I know this is at least the third season for the pile I’m pulling off now. I haven’t burned much the last few years. I took the top louvre off and placed the thermometer inside plenum area directly on top of the stove.
thanks Dmitry

 

[Dmitry]

It’s been pretty cold here lately so I’ve been running it hotter than normal. Right now there’s hardly any black anywhere on the glass. I’m not gonna lie I get some build up earlier in the season though. I bought a moisture meter a couple years ago and I split and measured a few pieces last fall. None were over 20%. I know this is at least the third season for the pile I’m pulling off now. I haven’t burned much the last few years. I took the top louvre off and placed the thermometer inside plenum area directly on top of the stove.
thanks Dmitry

Can you keep the air open a little bit longer to heat it more? The Fireplace should function properly with a certain temp established in beginning and cruising it for a while. In my case when I reach 600, i start to close the air until it 500, then leaving the air at this level and it burns and holds it 500 for a while,"cruising". The extension will help, but I suggest you need to reevaluate your technique.

 

[Caw]

I dont think STT is a very accurate way to judge when to shut air down. Every stove is different and maybe going hot first works for @Dmitry but I don't think letting is get to 600 before starting to shut down air is proper technique generally...you're sending tons of BTUs up your flue!

I used to do it that way too and it works but it's also wasteful. In my experience the best cues to start shutting down the air are visual. If you see secondary combustion starting or when the primary flames start to engulf the entire load its time to shut down the air. Shut it down until the flames get a little lazy but don't go out. You keep doing this incrementally until you reach your cruising temps then turn on your blower if you have one. Yes this technique is slightly more involved and may take a few extra minutes but you will get you the longest and most efficient burn possible without blasting through fuel and sending those BTUs up the flue.

Bottom line: STT sort of doesn't matter. It's primarily there as a safety gage to make sure you aren't over or under firing your stove. Don't rely on it! Use visual cues to manage the fire and the STT will sort itself out. The fire will tell you what it wants/needs....unlike my wife!

Also to the original question - Yes the few feet absolutely matters. Modern stoves NEED a minimum draft to function properly. Its not optional...they simply won't work right without it. I think you'll see significant improvement with a proper flue. Best of luck!

 

[Oaktree]

Thanks Caw!