Print

[MattyNH]

Sounds like a cool idea..But sounds expensive as well..After all a new OWB these days are 7-10K..

[willieG]

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?

[Scott7m]

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.

[Scott7m]

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.

[yoderheating]

 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. 

[ELEproducts.com]

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

[RSI]

I am interested. I don't think it will work but I have been wrong before. Lol

[ELEproducts.com]

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

[ELEproducts.com]

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

[yoderheating]

 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? 

[RSI]

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.

[yoderheating]

 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.

[RSI]

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.

[yoderheating]

 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.

[ELEproducts.com]

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