Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: Scott7m on September 30, 2011, 06:09:07 PM
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Got her lit about an hour ago, I'll let you guys know how it
performs! It does burn very clean, I can already tell that!
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You are going to love it. I started one for a customer last evening and after 10 minutes he was convinced it had went out but after looking again it was just burning that clean. Heat Master has done a really good job experimenting on how to get air above and below the fire to get that clean burn. Keep us posted.
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You are going to love it. I started one for a customer last evening and after 10 minutes he was convinced it had went out but after looking again it was just burning that clean. Heat Master has done a really good job experimenting on how to get air above and below the fire to get that clean burn. Keep us posted.
hey, on the two sliders on the back, where do
you typically set them? I have both of mine set about half
way
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That sounds about right, I've experimented with them in several different locations. I have customers giving me different accounts of what works well for them. From what I can tell so far about half way on both is good for dry wood and half on top and wide open on the bottom is better for green wood or coal. I enjoy experimenting with it and seeing what difference it makes.
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:) WOW. I am impressed.
Last night I built my first fire in it with some cardboard and a small arm load of seasoned sycamore that was split up pretty fine. It took it roughly an hour to get to 155. I then went back out to the stove last night around 9 and put in one piece of seasoned sycamore roughly 10" diameter, and beside of it I laid about a 10 pound lump of coal.
All night long I kept telling myself I didnt put enough wood in the fire, lows here were in the 30's. However, I noticed the fan in the house wasnt running longer each time as it would when the fire is cooling down. So at 9:30 I went out and was amazed at what I saw, the 10" sycamore piece was about 70% gone and the coal was still burning as well. Most of the small pieces of sycamore were gone but it was a longggggggg ways from going out!
I am really impressed with this unit, with the fully adjustable air control on the back I'm looking forward to playing with it. I have them both set about half now and its performing great, if you open the door with the fan on you can clearly see what a big difference the air blowing into the top of the fire makes. I know it's not a gassifier, but it's very impressive to how cleanly it burns with the fan on.
Looking forward to a longggggggggg cold winter!
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How about a comparison with the NCB-175?
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Hello everyone! I too have a HeatMaster. MF3000. My house is ~ 2000 sqft. Western red cedar siding, two story, 2x6 wall construction, so the insulation is decent. I started my first fire last night about 6pm. It was up to ~ 140F in one hour. I have a conservative nature and will only cut/use trees that are dead. Anyway, what I am getting to is, I had stuffed maybe 3 sticks of very dead white pine and 1 stick of white oak, equally as dead. All 4 stick were on average 6-7 inches diameter and all had lost their bark long ago. I fully expected a reload in about 1 hour. Was I wrong! That thing burned all night with the inside thermostat set on 74. I went out about 7 am the next morning and there was nice bed of red hot coals waiting for another refill of 4 sticks. Very impressed. As of now I love it! Very little smoke too. I will also post more info and data as I continue to gather it. This forum was very informational for me in the decision to purchase one of these stoves and hope I can contribute to help others.
Thanks,
Shawn
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How about a comparison with the NCB-175?
I'm not ready to draw those comparisons yet. We'll see as the course of the winter goes on. As far as I'm concerned the 175 is a very good stove, it's by far my favorite out of the NCB line up.
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Getting the same results with my CB. Restocking once every 24 hours. (4 pieces-split-approximately 4" round) There is at least two pieces left from the previous stocking.
It seems to make two burns in those 24 hours to get the water back up to temp. Of course I can't say "NO Smoke" But the burn times are only 10 minutes and with my location (on a ridge) the smoke does not linger long.
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Product Development, stage 2. (prototyping) I have a Heat Master MF3000. Out of the box it works very well. I am impressed. The objective is: Eliminate the firing cycle completely (this on and off thing with the draft motor and solenoid) . To do this will require a P.I.D. (proportional integral derivative) controller, designed from a 8 bit microprocessor and circuitry that can offer varying speed of the outdoor furnace fan induced draft from the factory installed Single-phase AC induction motor, either shaded-pole or split-phase type, along with a type K cold junction thermocouple providing closed loop feedback of the water temperature. These motors can be successfully controlled with PWM switching circuits. The P.I.D. controller would be self learning, knowing the soak time and ramp time needed to maintain a near constant water temperature taking into consideration ambient temperature and different combinations of wood and moisture content.
This would be a KIT product for most any outdoor woodburner/coal with forced draft. Outdoor wood furnace are single-stage firing that is either firing at full output (Plus or minus the setting from the mechanical flipper valve inline between the blower motor and point of entry into the fire box.) or completely off, a outdoor furnace with variable firing can give you the right size furnace for the majority of the heating season.
Any interest in something like this?
Thank,
Working Smarter, Not Harder :)
Shawn
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Sounds really cool.....and really expensive! Any idea on a dollar figure for something like this?
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It’s too early to project a cost. Actually, there is not a lot in terms of tangible hardware $$. Mostly labor in writing code.
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Would be interesting to see what it does but my guess would be that it would use more wood and make a lot of creosote.
If you still have it cycle but come on slow and turn off slow it might clean up most of the smoke.
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There is no cycling involved. P.I.D. is closed loop.
1. Proportional; looks at the present error.
2. Integral; looks at the past error.
3. derivative; looks at present and past errors to make a forecast.
4. The forecast value is applied which is the speed of the draft blower motor, which controls the burn.
5. go back up to step 1 and do it all again.
Error is: deviation of set temperature and actual temperature.
Maybe think of this as the governor on your gas or diesel generator, where the speed is controlled at a constant value to provide the 60Hz independent of various electrical load demands inflicted. In this outdoor stove product, speed is substituted with water temperature in the boiler being controlled. Controlling volume of draft using varying speed blower to maintain this set temperature without overshooting / undershooting set temperature.
Shawn
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There is no cycling involved. P.I.D. is closed loop.
1. Proportional; looks at the present error.
2. Integral; looks at the past error.
3. derivative; looks at present and past errors to make a forecast.
4. The forecast value is applied which is the speed of the draft blower motor, which controls the burn.
5. go back up to step 1 and do it all again.
Error is: deviation of set temperature and actual temperature.
Maybe think of this as the governor on your gas or diesel generator, where the speed is controlled at a constant value to provide the 60Hz independent of various electrical load demands inflicted. In this outdoor stove product, speed is substituted with water temperature in the boiler being controlled. Controlling volume of draft using varying speed blower to maintain this set temperature without overshooting / undershooting set temperature.
Shawn
Sounds pretty interesting.Have you done any actual trials yet?Just wondering if your still in the design stage or if you have a prototype out there working?You should start a new thread on your controller setup.More people would see it in a new thread.Let us know what you got going on :thumbup:
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Sounds like a cool idea..But sounds expensive as well..After all a new OWB these days are 7-10K..
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im thinking a 1000 gallon reserve tank in the shed, well insulated and then one wide open burn fire to heat it, no stop and starts and no cooling or warming the fire. 1000 gals. (close to 10 pounds a canadian gal) is about 10,000 pounds x 100 degrees should be about 1 million btu, that should heat you 24 hours on the coldest day of winter and who knows how long on an average day. if you had room in your basement for a tank this size (they have been built with wood and pool liners before) the heat lost from the tank would really not be lost?
just a thought..any others?
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I for one have no desire to keep my stove from cycling as it is of no benfit to me to jeep the stove at a constant temperature!
It sounds to me like a good recipe to make creosote, the whole point to me
about owb is simplicity, why take something simple and make
it complicated?? That's my take.
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However on a positive note, wow, this mf5000 is great, it uses very little wood, temps last night near 40 and it burned 1 8" piece of sycamore and a bunch of splinters from the splitter.
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I have to agree with Scott. Cycling a outdoor furnace where it is either burning wide open or shut down completely is the only way to go. The hotter the burn the better, it takes care of any creosote problems and reduces smoke. The the only time you wouldn't want a hot burn is if the furnace is inefficient and not able to capture the heat produced.
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Hello. For those interested. Software is complete and will be testing the motor speed controller portion of the P.I.D. temperature controller in the next couple of days. This will be a bench exercise in a controlled environment. It should be fun and I am sure there will be many bugs.
"It would be better if you begin to teach others only after you yourself have learned something."
--quote Einstein, 1928—
Shawn
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I am interested. I don't think it will work but I have been wrong before. Lol
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It is for sure I have been wrong too. Many times! I am glad we can admit it. Besides, what is the worst thing that can happen? A new low cost product owners can install simply and increase efficiency, reduce smoke and maintain tight temperature control of the water. I am not sure stove dealers like the idea so much? I'm sure there is an array of different reasons why.
Shawn
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Update on the P.I.D controller for my HeatMaster MF3000. Maybe this is a new method to control OWB stoves?? For some, change and acceptance is not without a price.
Prototype of the induced draft motor speed controller section is complete! Excellent results. This was being tested all day, Sunday. Firmware runs the draft induction motor in a random pattern. From complete stop to full on and varying everything between. Tested motor was a Dayton, 4.5 amp 125V squirrel cage fan. Advantages are combining a inexpensive 8bit micro controller and using phase angle control using a 16 amp TRIAC. Speed is controlled by pulse width modulation (PWM) signal that is generated by using the on chip timer and voltage comparator. The processor is constantly checking for zero crossings through the comparator. If this condition is true the output pin driving the TRIAC gate is cleared and the timer is started. The timer then counts a certain amount of time, after this time has elapsed, the TRIAC’s gate is driven turning on the fan until the next zero voltage crossing. With AC line frequency @ 60Hz, base frequency for PWM is 120 cycle per second. Varying the time on the timer varies the motor speed.
I have included two pictures. You can see (hopefully) on the oscilloscope the duty cycle of aprox 26%. In this test, the 26% is the minimal for this motor, it just has enough power to turn around the fan @ 1 RPM.
For folks interested in saving power. In the above scenario for the given cycle length, the fan is ONLY on 26% of the time and off 74%, turning 1 RPM. This means, power usage for 26 minutes out of every 100 minutes the fan runs at 1 RPM.
The old way of doing things is having some mechanical adjustable “butterfly valve” inline reducing the amount of draft to the fire, where the fan is still working 100% and static pressure is 80% of the capacity of the blower assembly.
If you are interested or have any questions on my project or are skeptical…… Please comment.
Thanks,
Shawn
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Maybe I misunderstand what you are doing but that fan isn't designed to do that is it? Wouldn't you need a variable speed fan?
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Maybe I misunderstand what you are doing but that fan isn't designed to do that is it? Wouldn't you need a variable speed fan?
Most variable speed fans are nothing more than a normal fan with an electronic speed controller on it.
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I admittedly don't understand much about this sort of thing. I do know that several years ago Heat Master tried a design where you could turn down the speed of the draft fan. It worked except that the fan would go out every few years. I have had to back and disable this and make them all run at full speed.
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I wondered about those. Did they work good otherwise?
They were just using a ceiling fan speed controller. I am not sure if they use the same method as mentioned here.
I have an electronic speed controller on my ceiling fan and instead of changing the pulse they just turn the motor on and off. When it is on low it is off for about 3 seconds and on for 2 seconds.
It works pretty much like flipping the switch on and off to make it run slower.
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They did make the fan run slower, however I'm my opinion they smoked more and didn't burn as well. I would think if you wanted to do a system like this you would want to try it out on a furnace designed to be a natural draft stove. Heat Masters seem to work best when burned hot and then shut off.
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Enjoyed the comments. ...
This is a reliable method to control single phase induction motor and permanent split capacitor (PSC) AC induction motors. Actually, it my add longevity.
Most variable speed permanent split capacitor start motor, like many found in furnaces are furnished with 3,4,5 and 6 different winding “TAPS”, whereas the electronics decide and choose which taps to use. Newer more complex furnaces use a PWM method or other types of motors, even DC motors to control their blower motors to circulate either hot or cold air in the living space. Like RSI said, it is similar to flipping the switch on and off. More precise is that it flips it on and off 120 times every second and the time that the switch is on verses the time the switch is off(duty-cycle) is the speed of the motor. The switching period of 120 times per second is an and must be in sync with the 60Hz (zero cross) of the AC line voltage supplying the power. Ceiling fans are also mfg both ways. Choice of speed by selection of different winding taps with the remote control, either winding TAPS or PWM methods.
The whole picture though is to control the draft motor with varying speed to control the rate of burn of the OWB by measuring water temperature while adjusting the draft motor speed to maintain this water temperature, also taking into account demands on the system from the user. Domestic hot water heating, garage, whatever may apply. EXAMPLE: My girlfriend jacking up the room temperature to ~ 78 Degrees!
Shawn
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Does this contraption translate into using less wood?
I just cut a cord of white oak yesterday, I'm good and sore! If adding this doesn't use less wood, I'll gladly pay another $2/month for my regular ole draft control.
I'm interested in an actual comparison of wood consumption based on similar outdoor temps with the oem draft control system vs your method.
For me, it all comes down to the wood!
Michael
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Fuel conservation is the goal. (Less Wood.) Smoothing volatile water temperatures from the crude installed controller alone is an interest worth noting.
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My Scenario:
Temperature dropped to approximately 39F last night. 8:30 PM. There were about 2, 1 gallon paint buckets of embers on the grate. I scattered them out nicely. For an experiment, I inserted a 8 inch diameter piece of white pine. This pine had been dead for years and was dry. The house thermostat was set on 74 (Girlfriend Is Cold) at the time of loading. When returning inside the house, I reduced the thermostat to 70F. Done! I woke at 6AM and the house is warm still at 70F degrees, I visit the Heat Master MF3000@ 6:30AM. Water temperature is down to 90F and the fire is out! The pine log is only 1/3 of the way burnt.
Here is what happened:
1.Outdoor temperature is seasonal, only 39F.
2.Reduction of indoor temperature, from 74F to 70F. (saving energy while sleeping)
3.One 8 inch diameter log of seasoned / dry pine.
4.One factory installed control that is not intelligent. It’s either ON or OFF.
With the demand on the MF3000 being minimal already, compounded by additional reduction in demand from setting the indoor thermostat from 74F to 70F. The furnace draft blower shuts down and the solenoid is relaxed, closing the draft valve. The furnace is now idle for a interval longer than the fire and embers can remain alive. Fire is now out, without any chance of ignition.
I believe the microprocessor controlled, variable draft fan speed controller product, operating in a closed loop mode will solve this issue completely. Huge benefit for folks heating domestic water in seasonal temperatures.
1st design on paper is complete, firmware is working well. Laying out circuit board. Physical product enclosure size is ~ 5” x 5”. Polycarbonate composition NEMA enclosure with a latching transparent water tight cover on a hinge. 4 SS ears to mount enclosure. 4 terminal strips. 1-POWER IN, 2-BLOWER OUT, 3-TEMPERATURE SENSOR IN, 4-SOLENOID VALVE OUT. Cables enter thru bottom, into sealed cord glands. LCD display on circuit board provides various information, visible through the enclosures cover. Mini- USB connector on circuit board to program the controller via PC computer and interface software.
Will this work??
Thanks,
Shawn
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What temperature did you have the boiler set to?
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Hi,
The boiler temperature was set on 150F from the installed controller.
I am using a 4 channel type-K cold-junction data logger. Measuring in-temp, out-temp ambient-temp and immersion-temp. Sample every 750mS. There is substantial over and under-shoot from what the display reads. The installed controllers reading is very smoothed. Response time is quite slow.
On a consumer level, this is good as the end user does not see the erratic temperatures.
Shawn
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I have included some temperature data take today from my MF3000 boiler. The PDF graft represents 250 samples. Sample interval is every 60 seconds. The point of measure is on the output pipe. Temperature control is set at 150F.
Shawn
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Ok?? What's the point? I really dont see what your trying to gain. Just seems like your trying tommake something simple complicated?
It takes x number of btu's to heat that water. Holding it one set temperature to me has no advantages at all, and many many disadvantages.
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Guess I kinda-sorta agree with Scott7m. I wouldn't want a gasser starting up to only gain one degree. They tend to get more efficient the longer they burn. Even the conventional ones tend to burn more smoke the longer they cycle. I think that what you are trying to achieve might not be possible without giving up some emissions. It takes a high temperature to burn smoke,and most OWB's would probably just start running efficiently when you would like to shut them down. I think that slowing down a blower motor or having some sort of variable dampener setting might really increase emissions. What you are trying to achieve, if I'm understanding it, is very admirable, but I think your starting point should be combustion chamber design(variable displacement somehow?). I think you'd need to be able to constantly monitor your exhaust gasses(enissions)and be able to communicate that data with the fresh air side to ensure a clean burn. If you get a prototype up and running, I'd be happy to use my 250 as a guinea pig for ya.
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I agree with Marty. I too wouldn’t want to start the furnace to only gain one degree. The idea here is that the speed of the draft motor is variable, from something like 1 RPM(so slow it’s the same as natural draft) to whatever the rated RPM is on the blower (maximum draft). The motor continues to run in a precise mode of varying speeds to maintain a burn that is required for the demand imposed on the furnace. The system no longer cycles on or off but maintains the water temperature much more “tightly” with this varying draft motor speed.
Like the curse control on your car. The set speed is maintained (boiler water temperature) and as we travel along various terrain of ascending and descending hills (demand on the boiler from heating house), the computer will apply a variable rate of fuel (varying draft motor speed) to the cars engine to maintain this set speed without overshooting or undershooting. This precise metering saves energy in a compounding way.
I agree also with Scott, why make something simple complicated? This is why this product would be simple for users to install and use.
Shawn
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I don't want to discourage your experiment but I have thought about this since you posted here and I'm mostly interested in your end point comparison.
I think your analogy to cruise control may even disprove your theory. The varying draft motor speed isn't the fuel in the case of an OWB, wood is the fuel. Yes, the draft provides oxygen required to influence the rate of burn of the fuel just as a car engine burns fuel in the presence of oxygen. If I understand this right, your draft control 'idles' at low rpm when the water temperature is equal to the set point. This alone will increase the rate of burn of the fuel (wood) vs. a shutdown of the draft fan and thus using more fuel (wood). It would seem to me that your stepping on the gas pedal while going down hill.
Additionally, will the variable fan control shut off completely at the set point or continue to idle at 1 rpm or whatever? If the draft fan continues to idle and the set point has already been reached, I wonder if this would allow enough oxygen to continue to burn the fire and increase your water temperature much higher than desired. Water boils at 212F, what effect would this have on an OWB system?
I could be thinking along the wrong track with your idea but ultimately, the draft fan has to turn off completely at some point or you may have some undesirable high water temps.
Keep us posted on your work! Keep it safe though!
Michael
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If ur idling at 1rpm that's way more than closed!
Something to consider, it takes x # of btu's to keep a firebox of temp at 150. If ur holding it at 150 or simply averaging 150, its still 150.
If your looking to make something more efficient as far as wood use, I don't think your looking in the right place.
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I can tell you up front what the end result will be. Creosote and smoke, and lots of it.
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I can tell you up front what the end result will be. Creosote and smoke, and lots of it.
:post:
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Wood Burner control update. The preliminary circuit board layout is complete. The circuit board is installed into a NEMA enclosure with a transparent lid / cover, providing visibility of the LCD display which has various information . Programming via computer using USB interface and software. Enclosure is ~ 6” x 6”. There are 4 cord glands/strain reliefs on the bottom of the enclosure where the cables enter and are electrically connected to 4 self contained terminal blocks. Factory or aftermarket type K thermocouple is used to measure boiler water temperature. Type J and others can also be used. The attached PDF will illustrate additional details.
Next: After more review, I will be sending out to have a small prototype run of the bare circuit boards made.
Hopefully in the near future, someone will be interested in testing the product, gathering user feedback to incorporate 1st production run .
Thanks,
Shawn