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Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 5:21 pm
by Jimeeh1970
Enjoying the lovely weather of NEPA today so I'm trying to squeeze more heat out of my Vf3000. Think I may be experiencing some coal quality issues. Anyway, does anyone know what the max recommended flue temp or the highest they've ever seen, for the Harman VF3000? Wanna go as high as I can without a meltdown.

Thanks,
Jim

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 7:29 pm
by McGiever
Thought it was all about a full burning grate and not pushing hot coals off the grate.

Watch adding excessive air... Could make fire box go Positive pressure and leak into house.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 7:40 pm
by BrotherDave
When burning at full tilt my flue temps run between 100 and 125 degrees after the baro.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 7:46 pm
by Rob R.
BrotherDave wrote:When burning at full tilt my flue temps run between 100 and 125 degrees after the baro.
Not trying to nit-pick, but flue temperatures after a baro will change depending on how much air is flowing into the baro...so it is not a good point of reference.

You can feed as much coal as the stoker will burn and still maintain an ash ring at the edge of the grate. Watch for clinkers when you start pushing it hard.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 8:18 pm
by BrotherDave
Nitpicking is fine. The vf is running full tilt right now, the grate is full. I keep the feed rate so it maintains an inch of ash before the grate ends. The temp on the tee at the flue exit is reading 150. Hope this helps.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 8:24 pm
by KLook
Mine would run about *230 right after the collar at a "T". the baro was in the open end of the T and the other went up the chimney. I could not run it hard enough to say it could have a melt down.

Kevin

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 8:25 pm
by oliver power
BrotherDave wrote:Nitpicking is fine. The vf is running full tilt right now, the grate is full. I keep the feed rate so it maintains an inch of ash before the grate ends. The temp on the tee at the flue exit is reading 150. Hope this helps.
I think you just about have it. My Kaa-2 is running full tilt right now. My flue temp in this cold snap are reading 150 before the baro.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 8:28 pm
by KLook
Keep in mind the boiler is only limited by the size of the stoker bed. I believe you could put a larger stoker in it and make more hot water. It would not melt an ASME rated vessel with 50 gal. of water in it.

Kevin

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 9:34 pm
by 2001Sierra
Keystoker 90 running full tilt 180 degrees before baro.

Re: Harman VF3000 Flue Temp

Posted: Wed. Jan. 22, 2014 9:41 pm
by coaledsweat
If you are worried about the stovepipe it will turn cherry red before it actually starts to melt. That said it will have to get north of 1000° to do that.

Re: Harman VF3000 Flue Temp

Posted: Thu. Jan. 23, 2014 7:07 pm
by Jimeeh1970
Reason I'm asking is I don't want to damage the unit. As I stated, I think I have some coal quality issues and I'm trying to push the thing as hard as I can. I have a custom control system and I actually have flue gas feedback which is sampled at about a foot after it leaves the stoker and I'm using it as a safety, just not sure where safe/pushing it to hard limit is. I currently have it set for 345 and it has reached it a few times though I just did a fill up from a different side of the pile and it does seem to be burning more efficiently.

Jim

Re: Harman VF3000 Flue Temp

Posted: Thu. Jan. 23, 2014 8:39 pm
by coalkirk
Jim, sounds like you are talking actual flue gas temps which is how I would measure it also. I think everyone else has been talking stove pipe surface temps. I measured mine after the baro and it was in the 260* range. I think before the baro is was about 345*.

Re: Harman VF3000 Flue Temp

Posted: Fri. Jan. 24, 2014 5:57 pm
by Jimeeh1970
Yes...I am measuring flue gas temp with an RTD inserted in the stack. Sorry for the confusion. Just wish I knew what the highest "safe" temp would be.

Re: Harman VF3000 Flue Temp

Posted: Fri. Jan. 24, 2014 7:58 pm
by KLook
I think I asserted before that you could not run it hard enough to ruin anything. Your flue temp is childs play compared to a wood fire in the same kind of pipe. How is it going to hurt the boiler vessel when it is filled with 50 gal. of water?

Kevin

Re: Harman VF3000 Flue Temp

Posted: Fri. Jan. 24, 2014 8:44 pm
by Jimeeh1970
Don't disagree with you kevin. Just looking for info. You as a VF3000 owner understands harmans highly technical owners manual publication which states don't go over three dots on the pusher stroke or damage to unit may occur. I'm currently a little over 2 and have seen variances where the the red hot coals are flowing over and the stoker is struggling to keep up vs today where I have 3/4" of burnt out ash but my stoker is over temping at 350* flue gas temp. I would really like to put the set point at 500* and let it fly but I'm just proceeding with caution.