Furnace burn times and stack temps?

[MT12157]

Hi,
Haven't been on in a long time but finally got a wood furnace in and now having some issues I cannot figure out. First of all it is a Daka 521 that I bought too cheap to even say new, I put a large fan and filter box that I scrapped up from a burnt out oil furnace, and used duct pipe as my stack so a good deal. I have a 35' exterior chimney with 8x14 flue tile. I have been burning for almost 4 weeks and cannot get more than 4 hours burn time. By 6 hours there isn't even a spark in this thing! I was getting stack temps of 650 degrees plus with the manual pipe damper completely shut. I added a barometric damper the other day which I have played around with following the factory recommendation of 2-6 wc adjustment currently at 6. I still get high stack temps before the baro. I can not get this thing to burn very long still. I have the air in the feed door and the automatic bottom draft open most of the time. it seems with 1 or both closed I just have a smoke box. What am I doing wrong? We had an old Oneida royal here years ago that always got 6 plus hours of a hot firebox but this I just cannot figure what I am doing wrong.

 

[hobbyheater]

This unit in the promotional literature shows that it can also burn coal . Are there grates that the wood burns on top of ?

 

[MT12157]

Yes it has a standard grate not a shaker in mine.

 

[maple1]

used duct pipe as my stack

What does that mean? Sounds kind of scary to me but maybe it's not saying what I'm reading.

That is a very high chimney. Have you actually measured your draft with a manometer? And how exactly are you measuring your stack temps? I suspect you have way too much draft and way too high stack temps - heat is being sucked up your chimney.

 

[laynes69]

Unfortunately in order to burn clean with this type of furnace, it needs to burn hot. On the opposite end, if you want a longer burn, it's going to smoke. Your flue temps will be higher before the baro, that's normal. If the unit has a forced draft, that can burn wood in a hurry. Unfortunately, most users have the same complaints. If you want a longer burn, you may have to reduce the air some and sacrifice a clean burn and sweep as necessary. Down the road, there are many wood furnace's on the market that are clean burners and offer nice burn times and high efficiency.

 

[MT12157]

Thanks for the replies. The pipe that came off the old duct work is 24 gauge from the 50's that actually seems thicker than the 24 gauge black pipe out there today. I have been measuring pipe temp with just a magnetic pipe thermometer and before the baro. I have not used a manometer to set the damper as of yet have been going only by the measurements where the weight is located. No forced draft by the way. I don't understand it I should be able to get more than a few hours burn time loaded up with oak and dry elm. If I open the pipe damper much all my heat goes up the chimney and will make that stove pipe go right up to 800-900 degrees which cant be right.

 

[laynes69]

If your old ductwork was/is galvanized, then I wouldn't use it as a flue pipe, especially with those temperatures. The zinc burns off the pipe, causing a harmful poisonus gas. You need black pipe for a flue pipe. With flue temps that high, your losing alot of heat up the chimney, but also flue temps will run on the higher side with a conventional wood furnace. Ours run 150-200 external, with a hot fire. Our old furnace would easily double that. The design plays a role, and the more basic design just can't capture the heat a newer efficient model can. If you bought the unit used, then check for possibly cracked welds, or other areas for air to enter. On a chimney that size, if it gets hot, it will draft very hard.

 

[Fred61]

If you're reading 800 to 900 degrees with a magnetic thermometer your true flue internal temperature must be exceeding 1000 degrees. Dangerous

 

[hobbyheater]

This is a older combination wood/coal/oil furnace.If you tried to slow the fire down, the embers would fall through the grates and the fire would go out, so there always had to be wood in the firebox and the draft just cracked open. Burning very dry wood with a brisk fire, flue temperatures most have been fairly high as there was little creosote build up. Just burning afternoons and evenings, this furnace would burn 6/10 cords per year.



This is the first fire in its replacement. The fire burns on a layer sand and can lay dormant for long periods of time. We live in an area where our heating season, by most people's standards, is a shoulder season. Burning 24/7 for the first 6 months, it looks like it will only burn around 5 to 6 cords.


This unit runs with very low flue temperature about 250 F, but again burning very dry wood. Creosote build up has not yet been a problem.
Have attached a PDF picture.

 

[MT12157]

Thanks for the replies. Yes the pipe "was" galvanized and burnt off with the rest of the paint curing on first fire with cellar doors open and such. The unit is brand new and factory direct minus fan and freight was 900 less than a tank or oil. I spoke to Daka tech today who btw was very helpful and nice. It was recommended I only use the bottom auto draft for wood and the door draft for coal. Also explained how to adjust the Barometric and don't panic if I get up to 6-700 temporarily during refueling. I adjusted the baro to open further and set it at 4.25 W.C. So far today so good we will see tonight. I am crusing at around 4-550 stack temp before the baro and 150-200 lower beyond it. Smoke from the chimney only with the stove reloaded with fresh wood.

If anyone is interested I will take pics of the setup.
Hobby heater , what make is the new furnace in the pic never seen one.


Also on barometric dampers, my oil furnace and water heater both go into a T and into 1 chimney, if a baro was added would there be one on each appliance or just 1 wherever it can fit?

 

[hobbyheater]

The furnace was originally made ( late 70's) in Northern BC and then was known as RSF but was resonantly sold to Eastern interests .Its not a gasification unit but I'm surprised at its efficient and clean burning ability. The wood being burnt is well seasoned Western Hemlock with a moisture content of under 7 % !

Attached PDF .

 

[maple1]

Mag temp guages read way low. Mine reads 100c less than the probe one beside it at 200c. Be very cautious using one of those to gauge your safety.

 

[lexybird]

Not sure what you expected with a economy furnace but A unit like that is only going to get 6 hours burn time ..maybe a couple more hours if packed to the gills and then it will burn dirty. . Galvenized duct pipe is foolish to be using as flue pipe it's not rated for those temperatures and contains zinc which can kill you . The correct black pipe is super cheap why even take the risk

 

[MT12157]

6 hour burn time would be fine, up until now I was getting more like 3-4. Apparently I had the baro and door draft adjusted incorrectly. The duct pipe I had used is 24 guage which other than the coating is the same as the black actually it seems thicker than 24. The galvanize burned off the first burn along with most of the paint which with cellar wide open didn't come in the house. As far as stack temps currently im 600 at early morning refire then 4-500 during regular burn. I think I will invest in the probe type thermometer though if that is the most accurate.