Modifying primary air intake on Enviro 1600

MNTIM

New Member
Oct 7, 2018
41
Minnesota
3B419680-20D6-46B0-8EC7-C935016D6039.png
Where to start... to set a few things clear- I have 23ft of SS liner in a clay tile flu. I have good draft -never back draft and I have plenty of leaks for air to come inside.

So my enviro from what I can tell has a very small primary air intake”I can see it when looking under the stove” - this air is provided from the bottom hole 3/4”x1.5” and goes internally up the sides and down the window as air wash Then enters the fire.
The stove always needs to be cracked a small bit to get going for 10 minutes with the door 1/8” at most open atleast until 250 stovetop untill I bother locking the door shut or it is a VERY lazy start.
I easily cruise 650+ on the stovetop. After I get some heat built up and good supply of dry wood.
Here lies the problem. After I get the stove hot- dial back the air or not I get allot of secondary action. But after the gasses are burned and it’s time to burn the charcoal down it takes forever- even with the primary air wide open..

During peak combustion I dial the primary air atleast 50% but during lighting fires and trying to burn down charcoal I simply need more air.

If I burn oak all day. By 6pm I have atleast a coal bed 8-10inches thick. And I reload around 350-400 but I want the heat of 550+ so maybe I just need to give the stove more time. But why not open the primary intake up in a fashion I can still completely control and close it. So during those other than peak combustion times I have 2-3x more air at my disposal.. I do realize I have a single control for both air supplies so I would be throwing the ratio between the 2 off but only for 90%+ primary air. I can increase just the 100% setting to 300% and by 75% have it back to the “stock” ratios

Now my lopi freedom has an air intake atleast 5-7 times bigger. And of course during peak combustion I have that dialed back atleast 80% but it also feeds an incredible amount of air for lighting fires or simply burning down the coals that are left in the stove.

Sorry for the lengthy post. Thanks for your time. I have attached the photo the manual has of the “airpath”
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,678
central pa
Anybody have an opinion on this or experience similar situations with new epa stoves?
What moisture content is your wood at? What you are describing sounds like wet wood.
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
My supply ranges
Maple 12-20
Oak 15-25
Poplar 12-20
Ash 15-20
I also have a good amount of extremely dry cedar for kindling and some fir from pallets for lighting fires and getting everything hot fast
 

kennyp2339

Minister of Fire
Feb 16, 2014
4,388
07462
What moisture content is your wood at? What you are describing sounds like wet wood.
Yes I was thinking wet wood or excessive draft pulling to much heat out of the fire box, I had that issue with my US2500.
When it was installed upstairs I never had coaling issues, full complete burns, I moved the stove down stairs because it was heating me out of the house, plus the wood mess was driving me crazy, well all of a sudden I started having major coaling problems, same wood, same dryness the only change was stove location and additional chimney height.
Just something to consider.
 

illini81

Feeling the Heat
Apr 7, 2017
323
Southeastern CT
What moisture content is your wood at? What you are describing sounds like wet wood.
+1

I have the Enviro Boston 1700. I'm not familiar with the Enviro 1600, but it seems like the design is very similar to my stove. I shut the door no later than one minute after re-loading. I also have to turn down the primary air 95-100% on nearly every full load, or I'd be in overfire territory (due to giving the fire too much air).

Also, I have recently found that if I open the air slightly (15-25% open) after about 4 hrs, I can keep the stove above 500 F for a full 6 hrs. Then if I open to about 50% at 6 hrs, I can keep the stove in the 400's for another few hrs. It's only during the very last hr or hr and a half of the burn that the stove temp drops below 400, and at that point I can turn up the fan to get extra heat (increase mass flow rate to compensate for dropping temp).

This isn't the way I normally run the stove - only on the days when I need another full load after 6-8 hrs, and so I want to get the BTUs out as fast as possible.

Contrasting the way I run my stove and the way you run yours (primary air 50% open, leaving stove door open for 10 min on startup) makes me think your wood is wet. How long has it been cut/split/stacked?
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
This could be the case.. the extra draft removes the heat and extra air from the firebox before it has a chance to burn up the coals I suppose. I will try slowing the initial burn down even more as long as I can maintain secondary burn and good heat of course
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
+1

I have the Enviro Boston 1700. I'm not familiar with the Enviro 1600, but it seems like the design is very similar to my stove. I shut the door no later than one minute after re-loading. I also have to turn down the primary air 95-100% on nearly every full load, or I'd be in overfire territory (due to giving the fire too much air).

Also, I have recently found that if I open the air slightly (15-25% open) after about 4 hrs, I can keep the stove above 500 F for a full 6 hrs. Then if I open to about 50% at 6 hrs, I can keep the stove in the 400's for another few hrs. It's only during the very last hr or hr and a half of the burn that the stove temp drops below 400, and at that point I can turn up the fan to get extra heat (increase mass flow rate to compensate for dropping temp).

This isn't the way I normally run the stove - only on the days when I need another full load after 6-8 hrs, and so I want to get the BTUs out as fast as possible.

Contrasting the way I run my stove and the way you run yours (primary air 50% open, leaving stove door open for 10 min on startup) makes me think your wood is wet. How long has it been cut/split/stacked?
All my wood is 2 years old.. I have over 15 cords split and stacked so i am always 2 years ahead. Also my upstairs stove “lopi” burns very similar to how described. I never have the door open for lighting fires.. same exact wood. But I can see the lopi physically feeds allot
More air through a way larger intake hole.

Also I believe the Boston 1700 has a pilot or doghouse air vent in the front center of the stove correct? Along with an airwash?
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
My issue isn’t so much the lighting - I can deal with that. But more so when I accumulate coals so thick I can’t load the stove. Then I’m stuck with a 300-350 stove for 4 hrs vs being able to burn those away faster. Also since my stove has a “false” cooktop which is a shroud that actually covers the top of the firebox and between that gap is where air exits from the blower. I have a IR temp gun and I have a small magnetic one on the front right corner just about the door- which when I have pulled my shroud off seems to be about 100-150 less than the actual top of the stove.
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
Yes I was thinking wet wood or excessive draft pulling to much heat out of the fire box, I had that issue with my US2500.
When it was installed upstairs I never had coaling issues, full complete burns, I moved the stove down stairs because it was heating me out of the house, plus the wood mess was driving me crazy, well all of a sudden I started having major coaling problems, same wood, same dryness the only change was stove location and additional chimney height.
Just something to consider.
What did you do to overcome this?
 

kennyp2339

Minister of Fire
Feb 16, 2014
4,388
07462
First is establish that you have an excessive draft .05-.07 " is generally the normal operating draft while the fire is on high burn, you test this with a manometer, depending on your setup you can install pipe dampers, I have 2, one right out of the stove pipe collar and one about 2ft above the stove top installed within the pipe, my draft was .017-.020 one damper would lower the draft to about .012 the second one would bring me into the .05-.06 zone.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,678
central pa
My issue isn’t so much the lighting - I can deal with that. But more so when I accumulate coals so thick I can’t load the stove. Then I’m stuck with a 300-350 stove for 4 hrs vs being able to burn those away faster. Also since my stove has a “false” cooktop which is a shroud that actually covers the top of the firebox and between that gap is where air exits from the blower. I have a IR temp gun and I have a small magnetic one on the front right corner just about the door- which when I have pulled my shroud off seems to be about 100-150 less than the actual top of the stove.
Shut the air down more. It will extend your burn increase stove temps and reduce coaling.
 

illini81

Feeling the Heat
Apr 7, 2017
323
Southeastern CT
All my wood is 2 years old.. I have over 15 cords split and stacked so i am always 2 years ahead. Also my upstairs stove “lopi” burns very similar to how described. I never have the door open for lighting fires.. same exact wood. But I can see the lopi physically feeds allot
More air through a way larger intake hole.

Also I believe the Boston 1700 has a pilot or doghouse air vent in the front center of the stove correct? Along with an airwash?
The Boston does have pilot air, but I believe (not 100% sure) that the pilot air is controlled by the primary air lever - so when the primary air is shut down, there's not a whole lot of pilot air. Also, my fuzzy understanding (or maybe just an assumption) was that all stoves have some sort of pilot air at the base of the flames. Are you positive yours does not? I realize it is not in the above image from the manual... but it could be that they just didn't include it in the schematic?
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
The Boston does have pilot air, but I believe (not 100% sure) that the pilot air is controlled by the primary air lever - so when the primary air is shut down, there's not a whole lot of pilot air. Also, my fuzzy understanding (or maybe just an assumption) was that all stoves have some sort of pilot air at the base of the flames. Are you positive yours does not? I realize it is not in the above image from the manual... but it could be that they just didn't include it in the schematic?
I am 100% positive mine does not have pilot air. I also have ran compressed air through my primary air passage Incase while the summer this stove sat in a guys shop unused and forsale a critter built a home inside the passage.. that schematic was mildly deceiving the first few times I looked at it also.. I also understand if I burn nothing but oak and reload at 400 I don’t really give the stove a chance and I may be expecting more out of it than it’s designed for. In terms of being able to catch up on the coals
 
  • Like
Reactions: illini81

MNTIM

New Member
Oct 7, 2018
41
Minnesota
First is establish that you have an excessive draft .05-.07 " is generally the normal operating draft while the fire is on high burn, you test this with a manometer, depending on your setup you can install pipe dampers, I have 2, one right out of the stove pipe collar and one about 2ft above the stove top installed within the pipe, my draft was .017-.020 one damper would lower the draft to about .012 the second one would bring me into the .05-.06 zone.
I Will absolutely look into this. But what I can’t quite wrap my head around is that if I had an excessive draft wouldn’t this be evident when I have nothing but coals and 350+ stove top. I would imagine the area of coals where the air hits them at the base of the door would be going crazy! Unless you think the air simply gets pulled out before it can even get to the coals. Very interesting theory and I will start reading threads regarding measuring the vacuum in my stove.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
18,678
central pa
Again if you shut it back more it will work much better.
 

Woody Stover

Minister of Fire
Dec 25, 2010
10,657
Southern IN
what I can’t quite wrap my head around is that if I had an excessive draft wouldn’t this be evident when I have nothing but coals and 350+ stove top. I would imagine the area of coals where the air hits them at the base of the door would be going crazy!
I think that a problem with too much draft is that the volatiles burn off faster and secondaries end sooner, plus heat also gets pulled up the chimney. Slowing down the air flow in the box lets the stove extract more heat.
23' is quite a bit of stack. How many elbows? Stove on the main floor or basement? Maybe we can guess at how much draft you might have.
 
  • Like
Reactions: MNTIM

MNTIM

New Member
Oct 7, 2018
41
Minnesota
It’s an insert in the basement
It’s 6 inch 316SS flex liner connected to top of the stove- straight up to my rain cap. One small bend in the liner “I think it shifts over from top of stove 8inches “ but that’s it. I have easily found 300+ temps At the top cap and very minimal buildup inside the liner at the very top other than in the cap.
 

illini81

Feeling the Heat
Apr 7, 2017
323
Southeastern CT
All my wood is 2 years old.. I have over 15 cords split and stacked so i am always 2 years ahead. Also my upstairs stove “lopi” burns very similar to how described. I never have the door open for lighting fires.. same exact wood. But I can see the lopi physically feeds allot
More air through a way larger intake hole.

Also I believe the Boston 1700 has a pilot or doghouse air vent in the front center of the stove correct? Along with an airwash?
Not trying to beat a dead horse... just trying to cover all the bases - I have found (and I think many others have as well) that 2 years is not sufficient for drying the really BTU dense woods, such as oak. So it is possible that the oak you're burning is less then ideal... which could be at least a partial source of your coaling?

When you say the wood is all 2 years old, was it split 2 years ago, or cut 2 years ago, sat in rounds, and then was split more recently? Also, has it been top covered?

I see the moisture percentages you posted - just to make sure, are those measurements taken on a freshly split face at room temperature (can take hours to warm up to room temp)? Or are they taken on the ends of the wood at outside temps?

The fact that you can leave the door open for 10 min without overfiring the stove, and that you can have the primary air open 50% at peak secondaries without overfiring still makes me think wet wood. Could be totally barking up the wrong tree though...
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
D66F42DA-4A4C-4C91-8EBB-06DE024C0F01.jpeg
My moisture contents Would be after the wood sits and warms up to close to room temp a day before it’s burned. Kind of a 2 stage program for the wood-
stacked “2yrs”
Garage 2-4 days
Either stove inside pile 1-2day until burned. This way I’m not burning wood starting at 0*
The high end of my moisture tests would be inside a larger 6-8” split thawed to room temp and popped open again. Sure a few may be higher here and there. But of course I don’t start fires with those. And my door has a few positions when locking, so when when I say door open when lighting I mean around 1/8th open at handle side. And I’m pretty sure my definition of an over fired stove is glowing external metal lol.
Also again my Lopi doesn’t even bat an eye at this wood. They both receive the same wood. And if I was to burn something I was sceptical at all about I would feed it to my Lopi.
 

MNTIM

New Member
Oct 7, 2018
41
Minnesota
I have burned about 30% less wood with the air control held back much further - window still clean and I have actually noticed I’m maintaining a higher temp for longer. But I’m not peaking during the burn cycle as high as before but maybe that’s ok. I’ll return after a few full cycles to see if it’s helping reducing excessive coaling.

Even after secondary’s have stopped and I only have crumblings coals I’ve been leaving the air control 10% at most and have held 400+ for 2hrs and then another 1hr until it’s nearing 350 and by then I’m impatient and stuff it full again. Obviously then I’ll go max air for a few minutes until everything in engulfed- then slam it down and watch the temp start to climb.

Picture is 25 minutes after reload and 15minutes with 10% air setting. Peaked near 600 on that thermometer and found closer to 650 above the door in the center about 25 minutes later and the stove stayed above 400 over 2 more hours.
That was a relative small reload with 2n/s and 2 small splits e/w

Again I’m using a IR but also a magnet on the face. I’m assuming I’m around 150 below actual stove top temp. Which I cant shoot or read without removing my surround and top shroud.
23175FF1-E706-4A41-99F9-DE42E07E79BB.jpeg
 

Woody Stover

Minister of Fire
Dec 25, 2010
10,657
Southern IN
I have burned about 30% less wood with the air control held back much further - window still clean and I have actually noticed I’m maintaining a higher temp for longer. But I’m not peaking during the burn cycle as high as before but maybe that’s ok. I’ll return after a few full cycles to see if it’s helping reducing excessive coaling.
I think it willl; If you stretch out the burn, the coals have more time to burn down.
Again I’m using a IR but also a magnet on the face. I’m assuming I’m around 150 below actual stove top temp. Which I cant shoot or read without removing my surround and top shroud.
You can open the door and shoot the top of the firebox from inside. I think that on the Buck 91, that would be about 150-200* higher than the meter I had above the door.
 
Last edited:

MNTIM

New Member
Oct 7, 2018
41
Minnesota
In some respects I think the stoves operates as it should.. I just want to always burn efficiently and get the most I can from the stove. My number 1 priority is always burning clean hot fires. I always assumed slamming the air down would bring the temp of the flu down more and potentially build creosote. Vs using a little more primary air. But if the secondaries are going and stovetop is 500+ I doubt much creosote is sticking to the walls anyways..
 
  • Like
Reactions: Woody Stover

Woody Stover

Minister of Fire
Dec 25, 2010
10,657
Southern IN
Your new technique will be put to the test, about the middle of next week! _g !!!