Secondary Air for Trident SF160

 
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JB Sparks
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Post by JB Sparks » Thu. Jan. 13, 2011 11:02 am

Cape, this is getting easier, I'll have to draw up the new brackets I made to hold the bricks in place, I could mount the pipes with 1" stand offs on the brackets. I hold the brackets in place with the load door latch bolt and drilled another hole on the hinge side of the door for the other bolt. When I turned the fire bricks vertical to get a deeper fire box I cut off the original brick brackets and ground the welds flush with the wall.


 
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JB Sparks
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Post by JB Sparks » Thu. Jan. 13, 2011 11:10 am

What size holes would be best to drill in the pipe? I thinking 1/8" holes about every 3" along the length of the pipe.

Thanks for the info Nortcan, I should have know this subject was discussed before.

 
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Post by nortcan » Thu. Jan. 13, 2011 11:17 am

JB Sparks wrote:What size holes would be best to drill in the pipe? I thinking 1/8" holes about every 3" along the length of the pipe.

Thanks for the info Nortcan, I should have know this subject was discussed before.
You can read : a good or not good idea, posted Nov. 29,2010
nortcan

 
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Post by CapeCoaler » Thu. Jan. 13, 2011 11:54 am

Sounds like a good start...
You can always make more holes if needed...
Aquarium air pump might be a nice test to give a bit of air pressure to the pipe...

 
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coal berner
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Post by coal berner » Thu. Jan. 13, 2011 12:08 pm

Why do you want to add another secondary air source you already have one that is what the air vents are on the loading door are for to bleed or burn off the coal gases on a reload of coal you open them up the air will come in from the outside of the unit which will wash off the gases up the chimney or light them and burn them off once the new coal is burning you can shut them or keep them cracked a little but I would keep them closed once the coal is burning.

The vents are also there for if you want to burn wood shut the ash door vent and use the top ones when burning wood
like on all wood & coal combo units that is why they are there .

Stoves boiler and furnaces that do not have air vents on the loading door /over the fire air are not meant or design to burn wood in them only hard coal . To prevent puff backs on these stove all yo do is open/crack the loading door for a few minutes until the gas is burned up or washed away then shut it .

Units that have blower fans above the fire are meant for wood or Soft coal. Also anthracite my be burned in them if there is a air vents or knobs below the fire like in ash door but the over the fire blower fan should not be used when burning anthracite.

But if you like projects go for it I don't think you will see much or any differents by using a pipe vs. the door air vents that are already there .
Last edited by coal berner on Thu. Jan. 13, 2011 2:41 pm, edited 2 times in total.

 
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Post by franco b » Thu. Jan. 13, 2011 12:15 pm

I agree on taking the air from a separate opening into the stove. Bleeding off primary air which is already restricted when set for a long burn I don't think would be effective.

There are two gasses we want to burn. There are the volatiles when coal is first heated and there is the CO formed in a deep coal bed under long burn conditions. For the latter I think the hotter the better.

Would be nice if you could design in such a way that several configurations could be tested before a final build. Testing is the hard part. Lacking apparatus to test flue gas you would have to fall back on careful record keeping of coal consumed, stack, stove, and room temperatures. A look at how some of the modern wood stoves have handled the problem might give some ideas as well. Some of the antique stoves also had arrangements intended to burn Bit. coal which would probably work with anthracite as well.

 
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Post by CapeCoaler » Thu. Jan. 13, 2011 12:31 pm

The idea is to close off the current secondary air and replace with an improved secondary air system...
The idea came from the DSM Circulator model...
The Big secondary air vents tend to dilute and cool the gasses...
Preventing a good secondary burn...
The smaller holes will hopefully be less cooling and better distributed...


 
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Post by wsherrick » Thu. Jan. 13, 2011 12:38 pm

CapeCoaler wrote:The idea is to close off the current secondary air and replace with an improved secondary air system...
The idea came from the DSM Circulator model...
The Big secondary air vents tend to dilute and cool the gasses...
Preventing a good secondary burn...
The smaller holes will hopefully be less cooling and better distributed...
I think the idea has been around for about 130 years or so now and was/is a well established practice. ;)
Last edited by wsherrick on Thu. Jan. 13, 2011 12:38 pm, edited 1 time in total.

 
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Post by AA130FIREMAN » Thu. Jan. 13, 2011 12:38 pm

JB Sparks wrote:AA130fireman and Capecoaler, The reason I was thinking of taking the secondary air from the ash pan area was to get preheated secondary air in the fire box. You guys think it is better to get the air from outside the boiler? That would be an easier retrofit if that is the case. I have added a combustion blower to the Harman and on reload it is likely to back puff if I forget to bank the coals or open the load door vents a little more than I usually keep them.
There would be no reason to have preheated air. Outdoor air is better, you would not be creating a vacuum inside the house(letting drafts in) and you keep the hot air inside, just like the idea of having a baro damper. If you have a combustion blower you could try an outdoor air source and pipe it to the blower and see if that would help.

 
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Post by LsFarm » Thu. Jan. 13, 2011 12:40 pm

I'd make the pipes from 3/8" pipe, put them in a notch cut in the firebrick for the vertical section of pipe's run..
use the second design. And get some caps for the exposed lower end [inlet] to the pipe.. make sure the threads for the caps are very deeply cut, so the cap can be threaded on all the way till the threads in the cap bottom out.. Then drill a 1/4" hole through the cap, and pipe.. this will be an adjustable inlet vent.. you just turn the cap to open or close the 1/4" hole.. You'd have to open the ashpan door to access the cap, but I'm not sure how difficult it would be to get to a pipe in the corner..

Having the pipe behind and protected by the firebrick is very important,, regular pipe would only last a week at best if the coal fire was touching the pipe.. and that's from personal experience.. so notch the edge/side/corner of the firebrick and slide the pipe behind it.. if the horizontal section lays on top of the firbrick that would be OK, there is not fire up on top of the brick, only heat and ash, and unburnt coal if you load it that deep..

If this is a big firebox,, you may even want to use 1/2" pipe. since you can adjust the air volume, you may find that you want more than a 3/8 pipe can supply.. I guess you could try to figure out how much air you are feeding the fire through the spinner vent.. but I'm not sure how to do the calculations..

I'd not go with fresh air from outside the unit untill I proved the function of the secondary air..

If you are burning nothing but anthracite, you might see some increase in combustion temps.. but if you were burning Bit coal,, you'd see a huge increase right after a fresh load of coal is added..

Too bad you don't have a viewing window to see if it is working.. like the DS machines with the vents around the front door window.. Or, do you have a window on the Trident ???

Greg L

 
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coal berner
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Post by coal berner » Thu. Jan. 13, 2011 12:50 pm

CapeCoaler wrote:The idea is to close off the current secondary air and replace with an improved secondary air system...
The idea came from the DSM Circulator model...
The Big secondary air vents tend to dilute and cool the gasses...
Preventing a good secondary burn...
The smaller holes will hopefully be less cooling and better distributed...
The secondary air should be close anyway once the new load of coal is burning with in a few minutes after loading the
coal so why add or upgrade to another one You would want to keep it closed once the coal is lit off no need to keep it
open all time Anthracite does not like over the fire air anyway the loading door vents are there to one burn off the coal gases on the new load of coal and two if you want to burn wood in the unit other then that they should be closed when the coal is burning Or if you want to Dampend down the fire then keep them opened .

 
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Post by JB Sparks » Thu. Jan. 13, 2011 2:32 pm

LsFarm wrote:Too bad you don't have a viewing window to see if it is working.. like the DS machines with the vents around the front door window.. Or, do you have a window on the Trident ???
Greg, thanks for the input, no the Trident does not have a viewing window but have been thinking about making a 3" window in the door. Haven't figured out all the details on that yet. but have some ideas.
coal berner wrote:burn off the coal gases on the new load of coal
JC, how much would you open the load door vents to assure no puff backs? This doesn't happen often but enough that I would like a way to prevent them. Sometimes I either forget to open the vents or to close them which is why I was thinking of another way to add secondary air. I do use the vents to dampen down the fire, this helps control the overshoot of the boiler water.

I burn only anthracite coal, no wood.

 
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Post by JB Sparks » Thu. Jan. 13, 2011 2:41 pm

Below are pics of the combustion blower I have added to the Trident. The up side to the blower is a shorter time from idle fire to high fire on a call for heat. I use a limit snap switch to control the blower, it is set to turn off when the flue pipe reaches 190*. That is long enough to wake up the fire but short enough to prevent clinkers. The down side is if I forget to bank the coals or open the load door vents I could get a puff back.

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Post by coal berner » Thu. Jan. 13, 2011 2:46 pm

JB Sparks wrote:
LsFarm wrote:Too bad you don't have a viewing window to see if it is working.. like the DS machines with the vents around the front door window.. Or, do you have a window on the Trident ???
Greg, thanks for the input, no the Trident does not have a viewing window but have been thinking about making a 3" window in the door. Haven't figured out all the details on that yet. but have some ideas.
coal berner wrote:burn off the coal gases on the new load of coal
JC, how much would you open the load door vents to assure no puff backs? This doesn't happen often but enough that I would like a way to prevent them. Sometimes I either forget to open the vents or to close them which is why I was thinking of another way to add secondary air. I do use the vents to dampen down the fire, this helps control the overshoot of the boiler water.

I burn only anthracite coal, no wood.
Just enough to leave fresh air in until the gas is lit or washed away up the chimney.
A 1/4 to 1/2 should be more them enough Just shut once the coal is burning like when you shut the ash door .
keeping the ash door open for a few minutes will catch the coal quicker it rev up the fire faster .

 
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Post by JB Sparks » Thu. Jan. 13, 2011 3:02 pm

Thanks JC, that's about what I do, just gotta remember to open them and then to close them back down. I think if I fit up a viewing window in the load door that would help.


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