Help Installing Koker - Plenum Opening and CFM

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roehrin
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Hot Air Coal Stoker Furnace: Keystoker Koker 160

Post by roehrin » Thu. Sep. 25, 2014 3:07 pm

I'm trying to get myself setup using my Koker 160 that I bought from a neighbor. I wanted to tie it into my existing oil furnace ductwork. I'm new to this but I really wanted to do it myself if possible.

I noticed that CoalLen adjusted his plenum outlet to fit an 8X18 collar. Keystoker Koker 160 Help Please! This makes sense because you can actually buy some ductwork pre-made to fit that dimension instead of the 11X19 opening that is already there. But then I was wondering how much on CFM output you are cutting down by restricting the opening to that size.

When I look at this chart http://comfort-calc.net/cfm_chart.html it seems that rectangular 8X18 you are only going to allow 800 CFM. The fan output for this stove is supposed to be 1400 CFM, but even with the stock 11X19 opening aren't we too small to get the full 1400 CFM? Why did Keystoker design it this way, or am I just not understanding the concepts of ductwork and airflow here?

Maybe someone can explain to me if this all even matters. I have about 2100 sq ft of house I want to heat and I don't want to choke my air flow.

 
CoaLen
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Post by CoaLen » Thu. Sep. 25, 2014 4:54 pm

Be aware the Koker internal chamber above the stoker grate measures approximately 4" x 26".
For what it's worth, I'm heating 1800 sq ft on a single floor and have had no problem with air flow using the
8 x 18 duct.

 
roehrin
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Post by roehrin » Thu. Sep. 25, 2014 5:00 pm

So the internal chamber at 4" x 26" is actually a bottleneck, too?

So I take it the fan is rated to 1400 CFM but would never really perform to that volume in a real world scenario based on the plenum outlet and internal chamber.

 
vulcan
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Post by vulcan » Thu. Sep. 25, 2014 7:53 pm

I custom made a plenum for my koker by using 1/2" angle iron as a base and mounting it directly around the opening. I used sheet metal screws to attach the sheet metal to it. I have three 8 inch ducts coming off the plenum heating close to 2000 sf. I am not sure about the technical cfm #'s but my thermostat holds a steady 72.

 
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McGiever
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Post by McGiever » Thu. Sep. 25, 2014 8:12 pm

You don't need worry what size is internal...forgetaboutit!

Size all your duct work by the book, though.
You wouldn't want that velocity in your duct work though out your house that the furnace mfg'r gets away with internally. ;)


 
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plumberman
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Post by plumberman » Fri. Sep. 26, 2014 1:27 pm

i would personally run with the 8x18 and call it good. especially if it is short run to tie into the existing duct.

 
roehrin
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Post by roehrin » Fri. Sep. 26, 2014 1:50 pm

I actually need to run about 8 ft to the plenum of my oil furnace and it's around a corner and somewhat tight a space. I was hoping to use a large diameter flex pipe connected to whatever I have mounted to my Koker.

I'm still trying to figure out the best way to actually mount the plenum, but I've seen some good ideas here. A pre-made 8X18 starter collar seems the most practical at this point.

 
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plumberman
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Post by plumberman » Fri. Sep. 26, 2014 2:08 pm

you might want to check a duct/cfm chart to see what you can get away with,try if possible to match the air flow of the existing duct as close as possible, flex duct does have a big drop compared to same size in tin. would 2-10" round metal ducts fit the bill?? don't forget it aint the space shuttle!!

 
roehrin
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Hot Air Coal Stoker Furnace: Keystoker Koker 160

Post by roehrin » Fri. Sep. 26, 2014 2:12 pm

vulcan wrote:I custom made a plenum for my koker by using 1/2" angle iron as a base and mounting it directly around the opening. I used sheet metal screws to attach the sheet metal to it. I have three 8 inch ducts coming off the plenum heating close to 2000 sf. I am not sure about the technical cfm #'s but my thermostat holds a steady 72.
Vulcan, how did you mount the angle iron to the Koker?

 
roehrin
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Post by roehrin » Fri. Sep. 26, 2014 2:39 pm

plumberman wrote:you might want to check a duct/cfm chart to see what you can get away with,try if possible to match the air flow of the existing duct as close as possible, flex duct does have a big drop compared to same size in tin. would 2-10" round metal ducts fit the bill?? don't forget it aint the space shuttle!!
According to a CFM chart, a 14" round would match an 8X18. So that's what I was thinking. Should I go even bigger on the diameter of flex?

I imagined an 8X18 rectangular plenum with a the flex mounted at the top of the plenum stretching to the plenum of my other furnace. You can see the transition in my image. It's got to go over the exhaust pipe and still fit under the stairs. (Note that the furnace is on a wheeled cart adding about 6" of height, so it will actually sit lower than it appears in the picture).
Capture2.PNG
.PNG | 994.5KB | Capture2.PNG


 
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McGiever
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Post by McGiever » Fri. Sep. 26, 2014 9:09 pm

:idea: If you must use the flex duct, it will be way better to use the flex with galvanize metal 90*'s, instead of flexing the 90*'s. :idea:

 
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Post by shanedoe » Sat. Sep. 27, 2014 3:36 pm

I'm only running two 8in. round going in and coming out of my koker. Heats my 1750sqft. fairly well. My question is will the heat cycle times shorten a lot by running bigger duct? Seems stove will cool down quicker with more air blowing through it. Is it all just a wash in the end .

 
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McGiever
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Coal Size/Type: PEA,NUT,STOVE /ANTHRACITE
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Post by McGiever » Sat. Sep. 27, 2014 7:44 pm

Longer fan cycles are good up to a certain point and then you may be sending/wasteing too much heat up the chimney. How does one tell when that point is reached?

My guess is the stove that runs on and off more has the cooler exhaust pipe. ;)

Go bigger ducts and have adustable on/off fan set-point's for fan is best. :idea:

 
vulcan
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Post by vulcan » Mon. Sep. 29, 2014 8:15 pm

Sorry for the slow response. I used the 1/2 angle iron as a base and to make it rigid. The angle actually faces in and it sits on flat gasket material then on the sides I attached 1 inch angle iron strips which are mounted to the top of the unit and to the 1/2 inch base. This is certainly a homemade one of a kind plenum but it works well for me and was made mostly by material that was available at no cost.

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