30-NC Stovepipe layout change opinions?

[NickW]

Hoping some of our resident chimney experts might chime in. I have been discussing this in the "what's in you stove" thread but guessing only the regulars there are seeing it. This is regarding our house in SE WI, not the cabin in the Northwoods. Stove is the 30NC (tube stove).

Wood is good. Mostly 16-17% on a warm fresh split. Have had a few slight sizzlers, but not many.

Problem - I feel like I lose too much draft on overnight burns as the flue temperature drops resulting in charcoal and smoked glass. Fully loaded for an overnight burn I usually have to get down to the air fully closed to keep it under control (flue temp under 900, stt about 650). During the cold windy snap I did hit a flue temp of 1000 for just a second. If I leave it closed I have few coals, half a stove full of charcoal, and smoked glass. If after it starts to settle down (about an hour fully shut) I open to 1/8 open I have half the stove full of half and half coals/charcoal in the morning and still a little dirty glass. If after the 1/8 open for half an hour to an hour I open to 1/4 open I have mostly coals in the morning. Thing is I have to start the overnight load so early to have time to get to 1/4 open that the house is getting cold by morning.

Solution? - I am considering making part of the horizontal run angled (see photo's). Stove top to center of horizontal is 42", center of vertical to center of liner is also about 42", insulated oval liner is 20'. Bottom vertical stovepipe is adjustable. 2 - 90 degree elbows adjusted to create 1 offset 90. If I adjust the bottom lower stovepipe down and add a short stub at the 'T' and attach one of the 90's on each end I can have most of the horizontal run at an angle (guessing 30ish degrees) and maintain clearance to combustibles.

Questions:
1. Do you think this will help my loss of draft as the flue cools and allow me to keep the air a little more closed on the long burns?
2. Will it make it harder to control when flue temps are up?

I theorize that the angled section won't affect draft much when the flue is hot, but should help the draft as it cools...?

 

[NickW]

Here's a closer more side angle shot showing the scale of vertical to horizontal better

 

[Highbeam]

You must have a quite tall chimney to be able to completely close the air on an NC30 and not immediately kill the fire. My NC30 is very controllable. When you close the primary air control what you're really doing is forcing more air through the secondary air system (the tubes). The chimney is still sucking about the same amount through the stove. With a key damper, you are able to bring the draft strength down to what the stove was designed for and the primary/secondary split can support a healthier fire at the base.

Rather than close the primary air fully, you would close the key damper and then leave the primary air more open so some air still washes the glass and feeds the fuel.

 

[NickW]

Yes, almost 24' vertical height total between stovepipe and liner.

On a full load after slowly shutting the air down in increments (1/2 hour to one hour after loading) I can run for about an hour fully closed, only secondary combination no primary's. Flue temps between 700 & 900, stt between 500 & 650. If I am perfect on my shutdown timing and increments and have a mix of hardwoods rather than all ash I can sometimes get away with only going down to 1/8 open, but it'll run with a flue temp of over 800 for 1 1/2 to 2 hours before coming down so I can open up to 1/4 open.

So your thinking a key damper may allow me to not need to get to fully shut? And then because I'd still have air coming through the doghouse I might not have to do so much adjusting through the burn..? I may still do the angle section as the horizontal gets some buildup in it.

 

[brenndatomu]

So your thinking a key damper may allow me to not need to get to fully shut? And then because I'd still have air coming through the doghouse I might not have to do so much adjusting through the burn..? I may still do the angle section as the horizontal gets some buildup in it.

Sounds like a good plan, all of it.

 

[NickW]

As I posted in the "work done" thread, damper installed. Couldn't change the pipe the way I needed to without moving the stove out 6", so we'll see how this goes.

Out of curiosity, with how I only fight overdraft on full loads (particularly when it's cold and windy), do you think I'll need to fully close the damper or put it at an angle? Obviously I'll play with it, just wondering where to start. Want to burn cleanly for as long as possible with less babysitting. 2+ hours before I can go to bed is a bit much.

 

[NickW]

After the first overnight burn it really seems to have done the job nicely 👍.

 

[Woodcutter Tom]

As I posted in the "work done" thread, damper installed. Couldn't change the pipe the way I needed to without moving the stove out 6", so we'll see how this goes.

Out of curiosity, with how I only fight overdraft on full loads (particularly when it's cold and windy), do you think I'll need to fully close the damper or put it at an angle? Obviously I'll play with it, just wondering where to start. Want to burn cleanly for as long as possible with less babysitting. 2+ hours before I can go to bed is a bit much.

Nick, my suggestion would be to buy a manometer. That way you can know what your draft is at any time...and can make adjustments accordingly. Dwyer Mark II is simple and works well.
I have massive overdraft with my set up. I installed an inline damper 25" above my stove top. I use it with every fire. I modified the damper so that more of the flow is restricted. Even with the modification, I do not get much reduction of the draft until the damper is closed 1/2 way. If 0 degrees is fully open, and 90 degrees is fully closed, my adjustments are mostly in the 75 to 85 degree position. Once in that range, very small adjustments effect the draft. That is just the nature of the beast for my situation. I close my damper based on my manometer reading. I let it run high a bit on start-up, then throttle it back at my fire takes hold. For my stove I aim for .05" WC or less with a good fire going. Fully open I can easily be in the .18" WC range.
I use the manometer reading and my digital flue temp reading to make adjustments to my damper and my primary air control. Different weather conditions, wind, and the wood in the stove all effect the draft. It takes experiments and experience to determine what works best for you. I feel that without having a way to measure your draft, you will always be guessing what to do. Good luck.

 

[NickW]

Nick, my suggestion would be to buy a manometer. That way you can know what your draft is at any time...and can make adjustments accordingly. Dwyer Mark II is simple and works well.
I have massive overdraft with my set up. I installed an inline damper 25" above my stove top. I use it with every fire. I modified the damper so that more of the flow is restricted. Even with the modification, I do not get much reduction of the draft until the damper is closed 1/2 way. If 0 degrees is fully open, and 90 degrees is fully closed, my adjustments are mostly in the 75 to 85 degree position. Once in that range, very small adjustments effect the draft. That is just the nature of the beast for my situation. I close my damper based on my manometer reading. I let it run high a bit on start-up, then throttle it back at my fire takes hold. For my stove I aim for .05" WC or less with a good fire going. Fully open I can easily be in the .18" WC range.
I use the manometer reading and my digital flue temp reading to make adjustments to my damper and my primary air control. Different weather conditions, wind, and the wood in the stove all effect the draft. It takes experiments and experience to determine what works best for you. I feel that without having a way to measure your draft, you will always be guessing what to do. Good luck.

Noted. Thanks!

I will comment that I rarely had the "lazy flames" on the wood that is often referenced. To keep flue temp under 900 I was running air fully shut on secondaries only, no primary's for 1-2 hours. Now I see exactly what lazy primary flame is. I have a "healthy" fire without worrying about overdraft and the stt is higher with a lower flue temp. Right now I have a 3/4 load of birch, maple, ash, aspen and box elder with the damper fully shut and air at 1/4 open. Nice secondaries, a little flame on the wood, flue at 667, stt at 570+/-...

 

[Highbeam]

Of course, even with primary air fully closed there is a bit of primary air going in. The nc30 has a doghouse with no regulation and the air wash slider control never fully closes.