EFM AF-150 Disassembly, Rebuild, Installation

 
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windyhill4.2
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Post by windyhill4.2 » Sat. Nov. 04, 2017 8:18 am

My EFM draft is .02 on idle,but almost immediately jumps to .05 when the stoker fires up.

 
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cntbill
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Post by cntbill » Sat. Nov. 04, 2017 10:32 am

Rob R. wrote:
Sat. Nov. 04, 2017 6:45 am
Nice job. -0.05 is fine for the draft (between the flue outlet and the baro).
Thanks, yes that is where I put the connector.

Dropped to 3 clicks and 3 1/2 air, draft went down just a touch between .04-.05

windyhill4.2 wrote:
Sat. Nov. 04, 2017 8:18 am
My EFM draft is .02 on idle,but almost immediately jumps to .05 when the stoker fires up.
Same here, .02 idle, then right up .05, well now between the .04-.05

 
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cntbill
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Post by cntbill » Sun. Nov. 05, 2017 8:35 pm

All is working well basement nice and toasty and using windowstats during the last two days at idle :D

But now on to the plenum / duct work. This is what I am planning and think will work ok. Going to try to explain...

Plenum size is 24" wide x 26" long, create plenum size of opening and go up from EFM to just below existing gas furnace duct work. Run a 8"x24" duct from EFM plenum to just below existing supply and cut an opening to about that size, this way the new supply duct will go under the existing duct and then have a flap that will flip open, shutting off air flow to the gas furnace, if gas furnace comes on from some dumb mistake it will close air flow to the EFM. Make sense?

Here is a couple of photos of gas furnace duct work
IMG_20171105_191914 (1).jpg

Existing duct work

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IMG_20171105_191926 (1).jpg

Same existing but different view

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Round ducts will be removed, they were for the Keystoker

Here is a real rough sketch of my idea/plan

Left part is looking straight at EFM and gas furnace, to the right past the squiggly line is looking down at duct work, and below that is like a cut out looking from the side.

But I just wonder if an 8"x24" supply is ok, the existing fiberglass supply trunk measures 9"x20" outside and then you need to subtract about 1 1/2" for the inside thickness. I really don't know the cfm of the gas furnace blower but it is about the same size. According to the specs in the EFM manual the blower is 1400 cfm at 6 teeth and 1600 at 7 teeth, blower size is 12 x 9, and the blower motor is 1/2 hp which I did verify.
duct drawing (1).jpg

Bad sketch of idea

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Rob R.
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Post by Rob R. » Sun. Nov. 05, 2017 8:42 pm

I think the manual is telling you what the air flow needs to be in order to use that feed rate.

3 teeth is a pretty light feed rate. Keep an eye on the auger pipe temperature.


 
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cntbill
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Post by cntbill » Sun. Nov. 05, 2017 10:00 pm

Rob R. wrote:
Sun. Nov. 05, 2017 8:42 pm
I think the manual is telling you what the air flow needs to be in order to use that feed rate.
OK, now that makes sense as I didn't quite understand how higher feed rate would raise cfm.
Rob R. wrote:
Sun. Nov. 05, 2017 8:42 pm
3 teeth is a pretty light feed rate. Keep an eye on the auger pipe temperature.
Just went and checked, feed pipe from stoker to coupler warm to touch, and much warmer closer to pot but still able to grab a hold of it without any discomfort. Coupler and pipe to bin not even warm.

Ok so running it low at 3 teeth is too low? So I'm guessing set it back to 4 and 4 and being that it is just pretty much idling it's not going to make much of a difference. But now a question, why running at 3 would make the auger pipe temperature pipe higher? hmmm guess more searching and reading is in order...

 
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cntbill
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Post by cntbill » Sun. Nov. 05, 2017 10:55 pm

Rob R. wrote:
Sun. Nov. 05, 2017 8:42 pm
3 teeth is a pretty light feed rate. Keep an eye on the auger pipe temperature.
After my last post which is about 45 minutes ago I turned up the thermostat up to get it running, and then I went down and set it to 4 teeth and just a bit more than 4 on air, 4 1/2 what it looks like, seems to be what it was set on before as the screw seemed to find like a flat spot like it just fit. And so now 45 minutes later I just came back from checking temp on feed pipe and what a difference much cooler.

 
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Post by StokerDon » Fri. Nov. 10, 2017 2:47 pm

cntbill wrote:
Sun. Nov. 05, 2017 10:00 pm
Just went and checked, feed pipe from stoker to coupler warm to touch, and much warmer closer to pot but still able to grab a hold of it without any discomfort. Coupler and pipe to bin not even warm.
You were headed down a dangerous road there Bill. As you decrease the feed rate, the further down the pot the fire migrates. This can damage the burn plates and even push the fire down the feed pipe. Some people have even installed temperature switches on the feed pipe to shut the stoker off if it gets too hot.
I don't think 3 teeth is a viable setting for the S-20 stoker.

-Don

 
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cntbill
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Post by cntbill » Fri. Nov. 10, 2017 3:14 pm

Don, Yes, Thanks go out to Rob for bringing that to my attention. Since setting it to the 4-4 it's been working good, pipe much cooler, but only idling since. Guess now that a little cooler weather is here and should have my plenum and supply duct done tonight I'll be able to fine tune it a little better. Keeping the house fairly warm with just blowing hot air in the basement, can't wait to see what it really can do.. :)


 
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Post by Rob R. » Fri. Nov. 10, 2017 4:52 pm

I have never seen an example where running at 3 teeth instead of 4 saves any coal. I don't feel it is worth the extra run time or heat in the air chamber.

 
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cntbill
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Post by cntbill » Fri. Nov. 10, 2017 5:29 pm

Rob,

Well the way I looked at it at first thinking that since it is just a hot air unit and running at idle I figured I didn't need the extra because I didn't need heat and just wanted to keep the fire lit. Didn't think of the pipe until you mentioned it and remembering the post showing a melted pipe and I sure as heck didn't need that. But as I mentioned pipe is cooler at 4, although my ash ring is good, I seem to see a bit of unburnt coal but, from I've read here that is normal for an S-20 on idle for extended periods. Once cold weather hits and it is running more and tuned in I'm pretty sure I'll see a lot less unburnt coal.

 
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cntbill
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Post by cntbill » Thu. Nov. 16, 2017 1:58 am

Made a little more progress, my flap/damper design took some figuring and my first attempt while I thought it would work ended up being a little to heavy. I was thinking that since this EFM has a constant fire there is always heat rising up through the plenum and wanted to allow the heat into the duct work and so my first design was like corrugated V grooves, but sort of butchered that one. So back to the drawing board and came up with a aluminum one with like 1" rails and that one works nice and as planned.
I did manage to make the plenum which was the easy part but get the supply duct in and attached to the fiberglass duct took some work. Have a little more to do on the supply duct as I have to pick up some more S cleats and get a real support ;) . And then on to the return.

The main duct trunk of the gas furnace both supply and return measurements on the inside are about 7" x 20" so the supply from the EFM I used a 8"x24" and I'm thinking, with the space I have I am going to make the return to the EFM 20"x 12". I think that should be effective as it is more Sq. In. than the supply. Also I'm thinking if necessary I could cut in a small duct in the return plenum.

Here is a few photos of what I did...

IMG_20171111_065213 (1).jpg

Steel one didn't work out to good

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IMG_20171111_215324 (1).jpg

Redesigned Aluminum one

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IMG_20171116_000824 (1).jpg

Plenum Supply

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IMG_20171116_000913 (1).jpg

Supply Plenum

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IMG_20171116_000937 (1).jpg

and another shot

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cntbill
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Post by cntbill » Mon. Jan. 01, 2018 1:08 pm

Just a quick up date... Got the return setup and This this is Awesome !

Only problem it pretty much only idles, runs the 2 minutes every half hour and keeping the house at 75* + and like the last few day where the temp is in the low 20's or below, it still runs very little for only a very few minutes.

So the thing is I think I read somewhere here about an EFM only running on idle there is some extra things that need to be kept an eye on ? Guess I need to go through the Boiler section again...

Once I get a couple photo's with the return setup I'll post them...

 
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Post by Rob R. » Mon. Jan. 01, 2018 1:16 pm

Nothing special to keep an eye on if you have a timer hooked up to hold a fire.

Glad to hear you are happy. These furnaces are really in a different league.

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