# Secondary burn achieved on Hot Blast 1500



## crewchief264 (Nov 7, 2013)

So I just put in a Hot Blast 1500 I got for 800.00 bucks after the 1st few load I was surprised how fast it burned up wood. I also have regency insert in my living room. But upgraded to whole house heat recently. So I am familiar with secondary burn and long burns on one load. Th Hot Blast as is is crap.... 5-6 hours max on a load of wood.

My setup: 15 foot double wall pipe-No baro- and manual, damper left open 75%-90%

Modifications:
1.5" secondary feed tube through front that splits to two 3/4" burn tube with less than 1/4" holes every inch on each side. I installed a 1.25" gate valve to control secondary flow
Front door vents completely blocked off
Nubs ground off ash door and set at about a dimes thickness






firebricks laid horizontal on sides
8 firebricks on top of existing shield
1/4" plate bolted to ceiling shield with 2 3.5" holes cut in it.

Just lit first fire with this set up and am seeing and holding a steady 500-600 on the firebox and the flue is at about 250...

My question: Is it normal to have flue temps that low.... It will climb to 400-450 but no hotter before the firebox gets to 600+

I am happy with it and will post how long the burn times are later.


----------



## stihly dan (Nov 7, 2013)

My Kuuma with secondaries Runs with 250* flue temps.


----------



## laynes69 (Nov 7, 2013)

Our flue temps on our Caddy run around 200 external.


----------



## Beefie (Nov 7, 2013)

All right this thread is useless without any pictures . I have a hot blast and always wondered how to get longer burn times. Do you have any pictures of the flames off the burn tubes.

Beefie


----------



## crewchief264 (Nov 8, 2013)

Beefie said:


> All right this thread is useless without any pictures . I have a hot blast and always wondered how to get longer burn times. Do you have any pictures of the flames off the burn tubes.
> 
> Beefie


Photos loaded up


----------



## crewchief264 (Nov 8, 2013)

Ok so I got a full 10 hour burn with coals still in the bottom and very little ash from 6 pieces of wood. The Furnace was still about 150 degrees and cycling on and off with the honeywell switch


----------



## Beefie (Nov 8, 2013)

Wow that is impressive, 10 hours would work awesome for me. Now Im just waiting for some more pictures to see how you made it. Do you have any better pictures of inside the firebox showing the additional fire brick and baffle?

Beefie


----------



## stihly dan (Nov 8, 2013)

crewchief264 said:


> Ok so I got a full 10 hour burn with coals still in the bottom and very little ash from 6 pieces of wood. The Furnace was still about 150 degrees and cycling on and off with the honeywell switch


 
If this is true? you may have a new carrier. Not many appliances can get more than an hour oh good heat per split.


----------



## blades (Nov 9, 2013)

I have a question as to the plate pictures do not really show to well its location. Is it right at the top of the side fire brick or further above. Could you do some general sketches nothing fancy as to internal arrangements. I total agree with your estimate of the unit in its original state, Believe mine is the1400, have not used it in the last couple years too much of a PIA, eats too much, and generally is uncontrollable, thanks to the crappy auto damper. Fought a bunch with it to no avail.


----------



## laynes69 (Nov 9, 2013)

It's possible to get more than an hour of heat per split. It all depends on the diameter and length of the splits, as well as type of wood. In mild weather when not much heat is needed overnight, 3 decent splits will keep the house warm overnight with enough coals for the morning. We had the 1500 hotblast like the poster for years, and it would take a 24" log and the firebox was twice as big as our Caddy. Last night, we loaded 6 splits, probably a little over 1/2 of our firebox and woke up 8 hours later with plenty of coals. The furnace wasn't putting out much heat at that point, but the house was 71 (thermostat for 72). After the initial fire stage of the burn, if a unit can hold the coal bed well and extract heat, it can extend the burn for some time.


----------



## TdiDave (Feb 22, 2014)

This is what I have put together. Any suggestions?
I was thinking about some type of ladder setup off the two stubs in the center
I miscalculated when I put the holes thru the back above the baffel, didn't account for the thickness of the baffle I measured from the angle iron attached to stove, so I could not completely line the baffle with fire brick.


----------



## flotek (Feb 22, 2014)

My drolet tundra / heatmax
Has a outer stack temperature of about 200 degrees. A good furnace will keep the heat in the unit and not send it out the flue pipe my dads hotblast 1557 has a stack temperature of. 600 -700 very inefficient because he's heating the great outdoors sending that good heat right up the chimney


----------



## blades (Feb 23, 2014)

Easy enough to cut the fire brick to size, right angle grinder and a masonary wheel to fit , grind deep groove, wide flat chisel in grove should snap it apart on the groove like any other brick. 
What are the 2 pipes above the baffle? preheat ?


----------



## Bushmans (Feb 23, 2014)

I like these threads. Guy at work has a wood furnace and says he has to feed it every three hours. Ugh! That would suck. I am currently retrofitting my stove. Baffle is in and secondaries are being researched right now.


----------



## TdiDave (Feb 23, 2014)

blades said:


> Easy enough to cut the fire brick to size, right angle grinder and a masonary wheel to fit , grind deep groove, wide flat chisel in grove should snap it apart on the groove like any other brick.
> What are the 2 pipes above the baffle? preheat ?


Yes that is preheat, I came in thru the back of the stove. I seen most have came in thru front down low to pre heat. I wanted to see if I could keep everything neat and up out of the way. (For some reason the photo loaded upside down)


----------



## Bushmans (Feb 23, 2014)

Bushmans said:


> I like these threads. Guy at work has a wood furnace and says he has to feed it every three hours. Ugh! That would suck. I am currently retrofitting my stove. Baffle is in and secondaries are being researched right now.



Brenndantomu what is to dislike about this?


----------



## TdiDave (Feb 23, 2014)

Cold weather will be back Monday will find out it this does any good. Couldn't really make it any worse ?


----------



## brenndatomu (Feb 23, 2014)

Bushmans said:


> Brenndantomu what is to dislike about this?


Nothing man, nothing! So sorry, I'm way into this stuff, done some myself, I must have moused over "dislike" inadvertently! I dislike the dislike button! BTW, I fixed it.


----------



## brenndatomu (Feb 23, 2014)

TdiDave said:


> Cold weather will be back Monday will find out it this does any good. Couldn't really make it any worse ?


Man, what'd all that set ya back?
Fire in the hole!
Oh, and Tdi, in my experience you will need to make a lot more air holes, or enlarge them, but if it is not too hard to install/remove, then try it out and see first.


----------



## Chris-PA (Feb 23, 2014)

brenndatomu said:


> Nothing man, nothing! So sorry, I'm way into this stuff, done some myself, I must have moused over "dislike" inadvertently! I dislike the dislike button! BTW, I fixed it.


Tryin' to steal my line? http://www.arboristsite.com/community/threads/i-dislike-the-dislike-button.252952/

LOL - I've seen so many of those I decided to comment about it over in support.


----------



## TdiDave (Feb 23, 2014)

I had a some of the black iron fittings and nipples laying around but I did have to buy about $50 worth of stuff. 
I have a total of 35 3/64" holes (10 down each edge pipe and 3 on each ladder pipe)
I fired it up tonight and to seem to get a lot of flames bouncing around the pipes and some occasional blow tourch from the holes. Any recomendationa on the direction the holes should face (strait down, forwar, rear word ?)
I don't have a strong suction on the 2 inlet pipes, should I? Is that a sign of not enuf holes?


----------



## Bushmans (Feb 23, 2014)

brenndatomu said:


> Nothing man, nothing! So sorry, I'm way into this stuff, done some myself, I must have moused over "dislike" inadvertently! I dislike the dislike button! BTW, I fixed it.



No problem! I kinda figured that's what it was just wanted to make sure. On my tablet it is almost impossible to hit the right button. I've done it enough times myself.
They really should do away with it. Seems kinda like a cheap shot. You should have to back it up with real words! Heaven forbid there might be an argument on AS. LOL


----------



## Bushmans (Feb 23, 2014)

Holes should point towards the flames (down and slightly in) is what I've read on other re-fabs. I've also heard that black pipe won't last very long but some use it to perfect the system before copying it to Stainless.
I was going to run my pre-heat along the bottom, up the front and then just under the baffle with holes drilled in the last section under the baffle. I would think your pre-heat on top of the baffle wouldn't get as hot as being in the main box where all the fire is. The hotter the air in the tube the better. Keep us posted! Burn times too?
I'm still under the impression that while secondaries burn better and cleaner it speeds up burn time.
Can't wait to get a first hand on a re-fab!


----------



## brenndatomu (Feb 23, 2014)

TdiDave said:


> I don't have a strong suction on the 2 inlet pipes, should I? Is that a sign of not enuf holes?


Any idea what your draft reading is? I have a tall chimney, so I have a baro to control the draft, once the secondaries were installed I had to reset the baro for a bit higher draft. Drilling larger holes will help though. Do you have a way of seeing the fire?



Bushmans said:


> I'm still under the impression that while secondaries burn better and cleaner it speeds up burn time.


I didn't find that, especially if the primary air can be cut way back after the stove (furnace) is in "cruise" mode. That is why I think it would be hard to do this without being able to see the fire, because it makes it easy to see if the secondarys are running rich or lean and then adjust the primary or secondary air flow accordingly. It can make things "fiddly" until you figure out the new normal.


----------



## laynes69 (Feb 23, 2014)

The holes in my burn tubes point forward to the door. They run parallel to the baffle, where the last tube shoots in both directions. You don't want too much air, especially if you have a tall chimney. I would see how it works before modifying anything else. Like mentioned, the wood doesn't burn up as fast because of secondary combustion. As the primary closes, the secondary air will produce more pull. The majority of the fire will occur under the baffle, where the smoke is consumed. If I plug my secondary air ports, the fire will almost go out, the chimney will smoke and heat output will drop. There's a significant difference with secondary combustion. There's been a few people modify their furnaces just like that one, and they ended up more than impressed. I was going to do ours, before I bought our new furnace.


----------



## TdiDave (Feb 23, 2014)

Draft is 0.05 a 0.06
I have the holes in the center pipes facing slightly forward now. 
Only way I can see the fire is thru the slots in load door draft control. I am getting some nice blue flames covering most of the underside of the baffle, never had that before. 
Flu temps 250, stove front holding about 400 

Not sure why the pictures post upside down.


----------



## brenndatomu (Feb 23, 2014)

Draft sounds perfect. NICE WORK!
If pics are from a phone, they will be upside down for some reason. Take them upside down they they will be right when posted


----------



## Chris-PA (Feb 23, 2014)

Nice job!


----------



## blades (Feb 24, 2014)

If you copy pics to a file then use an editor to rotate them and re-save problem solved, then up load from the new file.


----------



## KindredSpiritzz (Feb 24, 2014)

I been pondering doing this to my Norseman 2500. Just can't bring myself to actually drill holes in my furnace. Gotta work up the courage for that i guess.
Be interesting to see how long those pipes hold up to the heat. Another popular mod seems to be putting another row of fire brick along the top of the existing ones in the fire box, held up by a length of angle iron.
After looking at your pipes you may be able to tuck yours in behind your pipe on top, looks liek there might be enough room there.


----------



## TdiDave (Feb 24, 2014)

KindredSpiritzz said:


> I been pondering doing this to my Norseman 2500. Just can't bring myself to actually drill holes in my furnace. Gotta work up the courage for that i guess.
> Be interesting to see how long those pipes hold up to the heat. Another popular mod seems to be putting another row of fire brick along the top of the existing ones in the fire box, held up by a length of angle iron.
> After looking at your pipes you may be able to tuck yours in behind your pipe on top, looks liek there might be enough room there.


Funny you mention that as I just picked up 12 more bricks to do that exact thing. They will fit just behind the pipes, I may not get all 6 in as the elbow at the from an back stick out a bit further and I don't think I can squeeze it in.
I pipe has been glowing red so time will tell how long it will hold up.
First over night burn seemed better as I awoke to 74 and still a good bed of coals, usually temp will drop into mid 60's by morning. It was only one night so who knows but it seems to maintain 400-450 on stove front easier than before.


----------



## brenndatomu (Feb 24, 2014)

Shades of red, it's all about shades of red. I have seen black iron pipes red hot and be fine, but then a lil bit more toward the orange range and they will start to droop pretty quick. B.I. pipes have worked about 6 months or so at a time for me. I suppose it depends on how well they are supported too. I am gonna order some stainless pipe next time. I think I'm gonna order from these guys, they seem to have pretty good prices for small quantitys...http://www.onlinemetals.com/merchant.cfm?id=58&step=2&top_cat=1 Also, someone else here recommended these guys, they seem a bit higher to me, but still not bad http://www.metalsdepot.com/


----------



## KindredSpiritzz (Feb 25, 2014)

I'd like to see some pictures of where your pipes go through the jacket of the furnace in the front. How did you make it air tight? weld?? And i dont quite understand how/where you came through the back with your preheat air pipes. I'd think you'd either come in thru the front or the back, not both. Just having trouble picturing it.


----------



## TdiDave (Feb 25, 2014)

KindredSpiritzz said:


> I'd like to see some pictures of where your pipes go through the jacket of the furnace in the front. How did you make it air tight? weld?? And i dont quite understand how/where you came through the back with your preheat air pipes. I'd think you'd either come in thru the front or the back, not both. Just having trouble picturing it.



I came in thru the back not the front, I dint like the idea of coming in low in front, stuffing with wood would possibly damage the pipes.
I cut about 4" of threads on the pipe then double nut with washers to the fire box, then thru air jacket I installed a bushing to seal air leak, then the nipple that I can cap.


----------



## brenndatomu (Feb 25, 2014)

Bushmans said:


> I'm still under the impression that while secondaries burn better and cleaner it speeds up burn time.





Sorry about the photo quality, I only have a 1.5" viewing port and I couldn't spend too much time in photo position for fear of melting the camera. Anyways, you can see the single Oak split in the 7-8:00 position that I threw in 10-15 minutes earlier, is not really burning much, it is actually just smoldering on a hot coal bed with just a bit of lazy orange smoky flame due to the primary air being set to the minimum "over night" mode. The fireball that you see from 9-2:00, is secondary burn, and that, is a ton of heat being made off that small smoldering fire below, heat that would have been "up in smoke" before the baffle and air tube install, not to mention the side effect of a cleaner chimney!
Point is, since the primary fire is turned down low, the wood does not seem to be "consumed" any faster. Now, once the secondary flames die down after an hour or two, I suppose that that extra air could make its way down to fuel the primary fire, but by that time the wood is pretty much charred and in the beginning coal stage, and doesn't seem to be affected by air from above that much by that point.


----------



## TdiDave (Feb 25, 2014)

At what stove front temp would be need to get good secondary combustion ?
Would it be possible to have to few holes that push air to fast or hard out of the tube, my flames up under the baffle seem to move around rather violently.


----------



## redfin (Feb 25, 2014)

Can anyone point me to a good thread to explain this concept?


----------



## brenndatomu (Feb 25, 2014)

TdiDave said:


> At what stove front temp would be need to get good secondary combustion ?
> Would it be possible to have to few holes that push air to fast or hard out of the tube, my flames up under the baffle seem to move around rather violently.


How far are you cutting the primary and secondary back? I think I would want to put a key damper in the flue pipe and see what cutting the draft back a bit would do...
As far as stove front temps...who knows, depends on the exact model you have. I see 4-500, but that is through a heat shield, so...?
I have read that secondary combustion occurs at 11-1200*
EDIT, I just seen you already have a damper...


----------



## brenndatomu (Feb 25, 2014)

redfin said:


> Can anyone point me to a good thread to explain this concept?


If you do a search, you will find a boatload of secondary combustion content here on AS. Also, that other big hearth site would have a bunch too. 
Do you have specific questions?


----------



## redfin (Feb 25, 2014)

Well I have mostly passed over a lot of the threads regarding "secondary burns" due to the fact we were planning on moving and I didn't want to dork with the energymate box we use.

Looks like we will be here longer than we thought and after reading this thread it seems I could get better effieciency if I had somewhere to really start reading.

My box eats the wood. It has an ash pan and vent on the door that is all manual. I do not mind at all regulating manually just looking to get some longer burns overnite.

I willl search for some more threads.


----------



## KindredSpiritzz (Feb 25, 2014)

thanks for the pics Dave, i see i got yours confused with the OP as he has his coming in off the front. Whats the deal with the flex line bottom right in that 1st picture of your last post? I cant figure out what that would be for? I was thinking on mine about coming in from the front and running my pipes along the tops of the fire brick on each side to the back, then up and back towards the front. i think down lower like that might preheat the air better but still keep it above the hot coals. I'd also add some type valve to control the air inlet and probably play around with some type small fan (like a computer fan) on the inlet side to boost air flow. Love seeing mods like this, just gives me more ideas for when i finally bite the bullet and try it. One thing that always worried me was someone saying if you modify the furnace and burn your house down the insurance company could use that to balk at paying out.


----------



## TdiDave (Feb 26, 2014)

KindredSpiritzz said:


> thanks for the pics Dave, i see i got yours confused with the OP as he has his coming in off the front. Whats the deal with the flex line bottom right in that 1st picture of your last post? I cant figure out what that would be for? I was thinking on mine about coming in from the front and running my pipes along the tops of the fire brick on each side to the back, then up and back towards the front. i think down lower like that might preheat the air better but still keep it above the hot coals. I'd also add some type valve to control the air inlet and probably play around with some type small fan (like a computer fan) on the inlet side to boost air flow. Love seeing mods like this, just gives me more ideas for when i finally bite the bullet and try it. One thing that always worried me was someone saying if you modify the furnace and burn your house down the insurance company could use that to balk at paying out.


The flex line is from my domestic hot water pre-heat project. I have these coils in the hot air jacket to preheat the water going to my electric water heater


----------



## KindredSpiritzz (Feb 26, 2014)

oh my, you're like a mad scientist. Hows that water system working out for you? That deserves a entire thread on its own.


----------



## crewchief264 (Aug 29, 2014)

Bumping the thread from last year: I am getting ready to do some work on my wood furnace from last year... I will post pictures when it is done. I am going to add more firebrick and am contemplating re-working the secondary burn tubes..... 

the wood furnace worked very well last year and i got very good heat output and averaged about 8-10 hour burn times per load..... I have a large gate valve (the single most expensive piece) for the secondary tubes that I only leave open to about half and have all other air input shut down with the exception of the ash door which is only slightly cracked open (nubs ground off). I am looking forward to seeing what you other guys are up to with your projects.

Last winter was bitterly cold and windy last year, and they are saying this winter will be just as bad......


----------



## blades (Aug 29, 2014)

Haven't fired it up for the last 2 years, just been running the NC30 stove up stairs. Went through most of my Sugar Maple last winter. I just as soon pull HB out and get something else downstairs. I do have a old Englander 25xxx pellet stove here but haven't messed with to see whats up- I think the circut board might be bad as it will not shut down the feed auger with an empty hopper. 
My HB has a habit of going ballistic, not something i want going on when I am not around- so I do not trust it. Been all over the auto damper system to no avail. Plain useless. Never did get more than 4 hours of heat off it.


----------



## 350jeepcj5 (Nov 1, 2014)

ok this post has got me intrigued, rather then start a new one ill try to revive this one. tdidave, can you send me more pictures of this setup? i have a 1557m that i would be trying to do this to.


----------



## TdiDave (Nov 13, 2014)

350jeepcj5 said:


> ok this post has got me intrigued, rather then start a new one ill try to revive this one. tdidave, can you send me more pictures of this setup? i have a 1557m that i would be trying to do this to.



Made a few more adjustments. Ended up with about twice as many holes in the tubes (much better burn). Have most of the sides covered in fire brick, top of smoke shield is covered in fire brick as well. Easily get 8 hour burns of a nice hot fire with a few inch of hot coals for a easy relite.


----------

