Computer control the damper

[Heynow999]

Hi all

I'm new here.

I have a Pacific Energy insert like this one

(broken link removed to http://fireplacestop.com/product/pacific-energy-super-wood-insert)

I use it to supplement heating my house. I mainly heat with my natural gas furnace, but I light a fire several times a week in the winter. The insert is an EPA stove. What I want to do is set up an Adurino micro computer to control the damper so that the insert will automatically adjust to keep the fire in secondary burn.

Here's how I imagine it will work. The damper would be adjusted by a 12 volt linear actuator. I would place a thermistor somewhere on the insert that would read the temperature of the firebox. If the fire gets to hot, the computer closes the damper a few millimeters at a time until it gets to the right temperature, and opens the damper if the fire gets to cool. You get the idea. Instead of monitoring the fire and manually adjusting it, this would do it automatically. It might need two thermistors, one for the top end of the temperature range and one for the bottom end? The end of the actuator could be coupled to the damper with a magnet so it could be overridden if necessary, such as when you want to open the damper to add wood.

Some things I don't know. How hot should the fire box be to give a clean burn? What range of temperature would work for a clean burn? How hot is too hot? I have read about some people who are measuring the temperature in their stove, how are you doing that and where are you doing that?

I realize that this may seem like a lot of effort for little gain, but I like to tinker, and I like efficiency. I have never built anything with an Adurino and I would like to learn about them .This seems like a good application.

I am open to ideas about the design and need information about the temperature needed.
Thanks

 

[begreen]

This has been done in the past and is somewhat like the Quadrafire Adventurer control. I think knowing the flue gas temp would be a good input for deciding when to start turning down the air. It is more quickly reactive than the stove body.

 

[Nigel459]

I don't have enough expertise to offer any help, but I want to offer encouragement. This sounds like a very cool project. I wonder if sophisticated wood furnaces are controlled in such a manner.

Wait, I can offer the fact that secondary flames occur when the volatile gases reach ~ 1100F (600C). At least I think that's the number that folks talk about on this forum... haha.

Good luck! I'll be curious to see your progress and thanks for sharing

 

[begreen]

Wait, I can offer the fact that secondary flames occur when the volatile gases reach ~ 1100F (600C). At least I think that's the number that folks talk about on this forum... haha.

Correct, but inner firebox temps are harder to measure. The flue gas temp is a bit easier to measure and it correlates with secondary combustion starting. In our stove that is about at 500º. By 600ºF flue temp I usually have the air turned down at least 50% if not more.

 

[Heynow999]

Ok, thanks for the information.

Is there an accepted, reliable way to measure flue gas temperature that does not compromise my liner? I should have mentioned it, but I just installed the stove last year and I spent the big bucks on what I was told was a high quality liner. I replaced an old non-epa stove when my old liner got damaged during a chimney cleaning. I would prefer not to poke a hole in the new liner.

I went a read about the quadrafire adventurer. Please correct me if I am wrong, but it seems to me that the system works by choking down the fire when the room temperature gets too hot, with no regard to wether the fire is burning clean or not? I get it, they want to be able to say the stove will make you comfortable, but it seems like that would happen at the cost of efficiency.

My idea is that the only thing that matters is burning the wood as efficiently as possible. If the room heats up, too bad. The furnace will shut off for a longer time. Again, I only burn wood as a supplement.

Thanks

 

[illini81]

I’m planning on doing almost exactly what you’re doing (use a linear actuator to control the damper, with flue temp as the input). However, my goal is going to be a little different. My stove can burn a full load of wood in between about 6 and 12.5 hours. I would like to program several different settings for 6 hr, 8 hr, 10 hr, and 12 hr burn times. That way I can just fill it full of wood, and tell the stove how long I want it to last. The controller would keep the stove in different temperature bands, depending on the targeted burn time. For example, when I’m on a 6 hour cycle for really cold weather (single digits and below), I might want the stove to stay above 650 degrees (stovetop, I’m not familiar with my stove’s flue temps yet) for as long as possible, and then once the stove temp really starts dropping, the stove would open the air fully to burn up the coals as fast as possible to prepare for the next load. For longer burn times, the targeted temp and amount the damper is opened to burn down coals would change.

Similar to you, I’m not interested in controlling the fire based on the room temp. I’d like to control it based on desired burn time, which will of course correlate with room temp.

This doesn’t really answer any of your questions… but I wanted to say that I’m right there with you, and I’m excited to see how your project turns out.

 

[jetsam]

Somebody posted a thread about having done just that a while back, if I recall. It was pretty neat.

Blaze King stoves do all that without a computer (a mechanical bimetallic thermostat adjusts intake air based on firebox temperature). It is astonishingly useful for a full time heater; probably a lot less so when the stove is supplemental heat.

 

[Nigel459]

Somebody posted a thread about having done just that a while back, if I recall. It was pretty neat.

Blaze King stoves do all that without a computer (a mechanical bimetallic thermostat adjusts intake air air based on firebox temperature). It is astonishingly useful for a full time heater; probably a lot less so when the stove is supplemental heat.

Plus the catalytic combuster takes care of the efficiency part. Seems to be one of the OP's objectives....

 

[jetsam]

Oops, that recent thread was somebody using a raspberry pi to run his blower fans. It's worth a read anyway! Cool stuff.

 

[Nigel459]

You say you're striving for a "clean burn," i.e. efficiency. Is that to avoid smoking out the neighbours in TO? Or to maximize your wood value? For the environment?

Maybe you're like me and just enjoy tweaking and optimizing systems Just curious...

Hi all

I'm new here.

I have a Pacific Energy insert like this one

(broken link removed to http://fireplacestop.com/product/pacific-energy-super-wood-insert)

I use it to supplement heating my house. I mainly heat with my natural gas furnace, but I light a fire several times a week in the winter. The insert is an EPA stove. What I want to do is set up an Adurino micro computer to control the damper so that the insert will automatically adjust to keep the fire in secondary burn.

Here's how I imagine it will work. The damper would be adjusted by a 12 volt linear actuator. I would place a thermistor somewhere on the insert that would read the temperature of the firebox. If the fire gets to hot, the computer closes the damper a few millimeters at a time until it gets to the right temperature, and opens the damper if the fire gets to cool. You get the idea. Instead of monitoring the fire and manually adjusting it, this would do it automatically. It might need two thermistors, one for the top end of the temperature range and one for the bottom end? The end of the actuator could be coupled to the damper with a magnet so it could be overridden if necessary, such as when you want to open the damper to add wood.

Some things I don't know. How hot should the fire box be to give a clean burn? What range of temperature would work for a clean burn? How hot is too hot? I have read about some people who are measuring the temperature in their stove, how are you doing that and where are you doing that?

I realize that this may seem like a lot of effort for little gain, but I like to tinker, and I like efficiency. I have never built anything with an Adurino and I would like to learn about them .This seems like a good application.

I am open to ideas about the design and need information about the temperature needed.
Thanks

 

[Heynow999]

That sounds like a great idea as well. It would be virtually the same setup. I already have the actuator sitting in my parts bin, but I don't have a controller. I have looked into it a bit and it seems like an Adurino would work, rather than say a raspberry pi (which might work as well). I am just in the research phase. My next step is to figure out exactly what controller I should use, basically asking some questions on another forum. Let me know what you think would work as a controller.

Thanks

 

[yooper08]

I think the best way to approach this is to start logging data and continue to do it manually for a few days to determine what thresholds you need, but I agree with those saying measure flue temps as the easiest way to get accurate data.

One thing to consider in the damper logic is understanding the cooling down of flue gases as the fire nears the end of the burn. The question will be when do you want the damper to start opening back up, if at all. So, if you're doing something like illini wants and set an expected burn time, depending on how aggressive the burn time is, that'll determine when to open the damper more to burn down coals and maintain temp or slow the cool down.

Another thought is to add an input for room temperature. You could program a condition between room temp, damper, and flue gas temp to take over if certain thresholds are met, such as the room is too cold and flue gas temp is below a maximum > open damper.

You may also want to look into controlling the fan as well. Might as well automate that while you're at it

 

[jetsam]

trainman's codebase is in Python, but he hasn't started working on automating the intake air yet. It is listed in his project goals on github. Links to all of the above here.

 

[yooper08]

I'll just say that I'm jealous of those that have done this. I would do something like this if I had the time to learn how.

 

[Heynow999]

My goal is to get as much energy as possible out of the wood. I think all those others things will follow, less smoke, less creasote

 

[jaybz]

A simple PID loop in the programming will be your best option, this will also open the damper at the end of the cycle like Yooper mentioned.

 

[jaybz]

Also, it doesn't sound like you'll be able to predict exact burn times and maintain efficiency. Instead of a 6, 8 and 10 hr burn setting, you'd be better served with high, med, and low temp setting and burn time would be increased mostly through the amount of wood you load.

 

[jetsam]

Actually, BK owners get reliable, repeatable burn times at the same thermostat settings with a simple firebox thermostat hooked to an air flapper. Most any BK owner on the forum could show you where his 8, 12, and 20 hour settings are on the dial (but it's not the same for any two of them... every install and fuel source and operator is different).

It therefore doesn't sound unreasonable to me to say that he could automate a set burn time. It will of course be thrown off by variability in the fuel, in draft, and in operating procedures- but once you figure it out, you know how to compensate for this stuff. (I'm using pine instead of oak this load; turn down the thermostat a little and take a couple hours off the expected burn time...)

If efficiency is the goal, maintaining reburn temps is going to have to be prioritized above the user's setting for desired burn time. If it's a cat stove, this is probably a practical goal. If it's not, your low gear is named "smolder", and no intelligent air control is going to help you reburn wood gas at 450-600°F.

 

[illini81]

Also, it doesn't sound like you'll be able to predict exact burn times and maintain efficiency. Instead of a 6, 8 and 10 hr burn setting, you'd be better served with high, med, and low temp setting and burn time would be increased mostly through the amount of wood you load.

I actually think I will be able to get relatively reliable burn times. I can get reliable burn times right now... it's just manual instead of automatic. If I have a full stove, close the damper in stages, and don't open it back up at all, I will get a 12+ hr burn. If I open it a very tiny amount and leave it there, I will get around 11 hrs. And it gets more complicated from there (opening it up late in the burn).

I also may include settings for smaller loads which would not have a burn time associated with them (they'd just be Small/Hi Burn, Small/Med Burn, Small/Low Burn or something like that). Those settings may or may not be duplicates of the settings for full loads, and would be there primarily for the benefit of my wife.

Agree with Yooper08 that it's gotta start with data logging.

 

[AlbergSteve]

That sounds like a great idea as well. It would be virtually the same setup. I already have the actuator sitting in my parts bin, but I don't have a controller. I have looked into it a bit and it seems like an Adurino would work, rather than say a raspberry pi (which might work as well). I am just in the research phase. My next step is to figure out exactly what controller I should use, basically asking some questions on another forum. Let me know what you think would work as a controller.

Thanks

Make sure you check these guys out, they're in TO and often have sales on Pi and Arduino.

http://canada.newark.com/c/development-boards-evaluation-tools/embedded-development-kits-accessories

 

[jaybz]

I don't doubt that a BK can get consistent burn times. It's modulating the airflow based on firebox temps and winding up at a consistent burn time. I'm proposing the same thing with electronics. Measure the firebox or flue temp, set a desired temperature as the goal, and modulate the air damper to bring the measured temperature towards the goal. It would be a fancier bimetallic thermostat with much more user control. Calibration to get to a set burn time would really just consist of setting a temperature setpoint and seeing how long it'll run at that temperature. It would be the same as the trial and error to determine the 10 hour burn setting on a BK.

 

[Highbeam]

I don't doubt that a BK can get consistent burn times. It's modulating the airflow based on firebox temps and winding up at a consistent burn time. I'm proposing the same thing with electronics. Measure the firebox or flue temp, set a desired temperature as the goal, and modulate the air damper to bring the measured temperature towards the goal. It would be a fancier bimetallic thermostat with much more user control. Calibration to get to a set burn time would really just consist of setting a temperature setpoint and seeing how long it'll run at that temperature. It would be the same as the trial and error to determine the 10 hour burn setting on a BK.

The Kuuma wood furnaces do this with a temperature sensor to electronically control the intake. You set the appliance to a desired output setting and the electronics strive to maintain that temperature. The intake damper appears to have several positions vs. infinite opening sizes.

 

[WES999]

I did something liker this on my Regency, not really a computer but a temp controller and a timer activating a HVAC damper controller.

Mine used a TC in the flue to to turn on the damper controller, and close the air control a small amount when the flue temp reaches 875.

After a time delay if the temp was still above 875 the the air would be closed some more, the cycle would repeat until the temp was under 875.

Worked really well. Now I have a BK it controls it's self .

I don't think a thermister will work, not rated for the required high temp. Flue temp can be over 1000.

With a tube type stove I don't see the point of trying to regulate the stove by the room temp.

On my stove the more you close the air the hotter it gets.

Cheers

 

[coutufr]

What happen if there is a power outage?

 

[brenndatomu]

The Kuuma wood furnaces do this with a temperature sensor to electronically control the intake. You set the appliance to a desired output setting and the electronics strive to maintain that temperature. The intake damper appears to have several positions vs. infinite opening sizes.

Yes, the setting of the computer and the overall weight of the wood load put in determine burn time.
Primary air damper door has 4 positions, closed, low, med, high.