Time to control burn

If say you increase the temperature from 70* from idle (no flame) to 75* how long is it suppose to take before you start to see a flame on the coals?


This morning I got up and turned the temperature down from 76* to 74* and for over an hour the flames continued to dance and the temperature continued to raise up to 81* before finally settling down. Is that normal? The house got wicked hot and there just seemed like there was nothing I could do to get it to slow down.

Yes, that is the quite a bit of overshoot.

It's easy to control it at a set temp then raise or lower it all the time. I leave mine alone, maybe raise 1-2 degrees and leave it there for a while. We keep it at 68-70 most of the time.

What's your settings? Min/Max etc...

My min/max is 6/35.

That;s not too far off of my settings (min. 8/ max. 45). Different stoves though.

You might be able to bump the max up a bit to give a bit more feed rate to get the temps up faster.

As long as you are not raising the temps too much at one time, if you are doing a big temp. swing lke 5-10 degrees, it will probably do that. I wouldn't go more than 2-3 degrees and let it settle for at least an hour and see how long it takes to come up to temp. Coal takes time and the system has to adjust accordingly.

Especially if it was turned up and hadn't reached the setpoint, then you turn it back down in the middle of its cycle, it will take a while to re-adjust and then cause it to overshoot as it did, since it is still thinking of feeding a lot to catch up. it has to ramp back down.

Especially if it was turned up and hadn't reached the setpoint, then you turn it back down in the middle of its cycle, it will take a while to re-adjust and then cause it to overshoot as it did, since it is still thinking of feeding a lot to catch up. it has to ramp back down.

Maybe that is what I did, changed it in the middle of it's cycle before it finished getting up to temperature? It warmed up a little more then expected and tried to prevent the house from getting too warm before the wife was going to sit down and have breakfast. She doesn't like it hot.

Last night it was low around 40 and I have my min at 6 with my draft at .02wc on LL Econo with my thermo set to 70. It was 72 in the house all night with a FR of 0. I can't go any lower on the min and continue to maintain a safe draft. I am afraid my wife is going to open the windows in the house today. I now keep my thermo set at 70 all the time. Maybe when it gets colder I will change the set back in the evening but now I get a nice even heat with staying at +/-1 deg (til last night)

That great if you can just idle it and maintain 70 Degrees!!! it should work better once it gets colder outside.

Alot depends on where you have the t-stat located. If it takes quite a while for the t-stat to see the increase in heat from the stove the stove will continue to feed faster and faster to try to satisfy the t-stat. By the time the t-stat sees the temp has risen the stove is already stoking pretty hard and will give you a large temp overshoot.

Below shows the position of my thermostat in relation to the stove. I have had my thermostat @ 69 and its has been 71-74 in the house (depending on temp outside) with my FR reading 0 all the time. It is now 23* outside. All my walls are framed with 2x6 walls. I am not burning any more than maybe 22-25 pounds/day with the Econo now. My house is a 1350sq ft raised ranch. Total footage with partially insulated basement is twice that. I have a Magnum running in the basement in the opposite end on the house keeping the basement 65-70 while ducting the master bedroom directly above it.Burning 25pounds/day in that stove. It is about 67* at that end of the house upstairs. So, all in all, 50/day heating 2700 sq ft comfortably.

Mark

That's awesome! My Hyfire I easily rips thru 60-80#/day when below 30. !!

After having run my stove for it's first winter I have learned a little more about my stove. First off I have my thermostat as far away from the stove as the cable would let me, which is still in the same room. I don't think my problem with overshoot is due to the thermostat not feeling the heat quick enough but rather it continuing to feed at a high rate once the set temperature as been reached. On days like this where there is a little chill in the air and I wish to turn the stove on just to take that chill out is where it's the easiest to measure the problem. For example, it's 66* in the room and the temperature is set at 71* after turning the stove on full temperature will be reached within a half an hour, but after an hour or so the temperature in the room can be as high as 83* and the stove is still feeding at 84%. Once she gets around to backing herself down it'll just idle and easily maintain the set temperature, but the problem I have with this automated coal control is it just doesn't seem to respond quick enough to what ever the temperature is set at. Even during the winter the stove will continue to feed at such a high rate once the temperature as been reached. Isn't the whole point of having a temperature coal feeding control to help make the system more efficient while at the same time minimizing the amount of time an operator as to be touching the stove? By continuing to feed and basically waste coal by needlessly burning it just drops the efficiency down while increasing cost's from burning the extra coal and making the operator have to do more work by emptying ashes and filling the hopper.

Is there a way to make the coal control respond quicker to the indoor temperature?

Hi Adam, we're sorry you're continuing to have overshoot problems. Did you ever call us to discuss the problem and have us help you get things under control? We do what we can on the forums here, but if you have a persistent problem like that we like to talk with the customer on the phone in real time to try and troubleshoot the issue.

In the Spring and Summer "off-season", I'd strongly suggest backing your MAX setting way down. The stove is capable of producing far more heat than you require to maintain that 70 degree setpoint, and given the control's "sluggish" response to setpoint changes and settling on the setpoint when firing up the stove you are going to have very large overshoots unless you dial that MAX back significantly. Even with the MAX reduction, expect some overshoot. In addition to the significantly reduced the MAX setting, I'd suggest starting with a setpoint at or even below current room temperature, starting the fire, and letting it settle to idle FR, then adjust your setpoint up as desired. Also, given the relatively warm outside temperatures, you will need to increase your MIN setting a bit from what you use in the winter in order to maintain proper draft. If you are using a powerventer this increased MIN setting should not be necessary.

Reducing the MAX setting is usually the best way to handle an overshoot condition with our control. In some cases, particularly where the stove is undersized for a house, the use of the HLF setting can be helpful. However, diagnosing overshoot problems during the Spring and Summer is going to be very difficult given the low load demand during these seasons. It creates a situation where the BTUs released in getting the stove going (which depending on technique can often involve burning off a nearly full grate of coal as part of getting it going) can result in overshoots.

We're confident that the control does provides fuel savings we claim through our superior tracking of daily and seasonal demand fluctuations and our control's ability to dial up varying levels of fuel feed to match this demand. However, this strong tracking ability, coupled with the need to be very conservative in our tuning to make sure our control works in the broadest number of installations, has resulted in sometimes overly sluggish responsiveness to setpoint changes. While we do have some ways of reducing overshoot problems when they are encountered, we recognize this is a problem area for the control and continue to work to solve the problem. It is a tough problem to solve, though, while maintaining our tracking capability, relatively easy setup and control options, and maintaining steady control in all the possible installations our controls are used on. This area of improvement is our top priority in continued development of the Coal-trol Digital.

If the MAX setting reduction and suggested fire starting procedure don't work to reduce your overshoot problem in this off-season use of the stove, you can maintain a low fire by going to the MIN screen to force the stove to idle and using it as a manual feed adjustment. It isn't ideal, but it is a last ditch option to use when all else fails.

Lastly, make sure to clean the stove, flue, and chimney/powervent when you shut it down again. If it is left uncleaned and not burning for more than a couple days then rust may begin to build up on stoker and venting components and create a bigger cleaning headache when you do get to it.

I didn't call on it, since the issue was just basically in the mornings when it changed from the night setting to the day setting and it was usually on it's way down to the normal temperature by the time we got up. I changed my max setting from 6/40 to 6/30 and I'll see if that helps. It's suppose to be in the low 30's the next couple of nights with a frost warning so I'll more then likely be firing her up one of these nights.

We're confident that the control does provides fuel savings we claim through our superior tracking of daily and seasonal demand fluctuations and our control's ability to dial up varying levels of fuel feed to match this demand. However, this strong tracking ability, coupled with the need to be very conservative in our tuning to make sure our control works in the broadest number of installations, has resulted in sometimes overly sluggish responsiveness to setpoint changes. While we do have some ways of reducing overshoot problems when they are encountered, we recognize this is a problem area for the control and continue to work to solve the problem. It is a tough problem to solve, though, while maintaining our tracking capability, relatively easy setup and control options, and maintaining steady control in all the possible installations our controls are used on. This area of improvement is our top priority in continued development of the Coal-trol Digital.

I guess I don't understand what the problem would be to get the control to simply back off the feed rate once the set temperature has been reach? Overshoot seems it would simply be the coal continuing to burn very hot once the set temperature has been reached thus increasing the temperature beyond the set point. The problem isn't an overshoot issue but more of a glitch. For example it's like someone using an old fashion temperature gauge on the wall to try and maintain their set temperature they wish to have in their home while using a wood stove. Once they start the stove and the wood is burning and the burning rate increases thus causing the temperature to continue to raise and go beyond their desired set temperature and once their room is hotter then what they wanted, they now decided to act like the coal control does by continuing to throw more wood on the fire for the next hour or so gradually slowing down as time goes on until finally making the room a good 10* hotter and then letting the fire just idle.

My stove can and has just idled for days at a time when the temperature was right in the middle of being too hot to turn it off and too cold to not run it. If you have an oil or gas boiler, water heater or even an oven none of them continue to make heat once the set temperature has been reached, I don't understand how it simply doesn't just stop feeding once the set temperature has been reached, it's not like the fire is just going to burn out and you'll have to relight the thing.

We're working on it.

It isn't as simple as going to idle when the setpoint is reached. Consider that an overshoot is still going to occur if it goes to idle once setpoint is reached. To eliminate it the feed has to be dialed back ahead of hitting setpoint. This is not an easy thing to decide in a controller with limited information. People do this all the time, but they either consciously or unconsciously take into account a lot of information that the control simply doesn't know.

Also, if you go to idle, then the stove will eventually not be producing enough heat to maintain temp. What should happen then? Max fuel? Ramp up? How long should it ramp up? To eliminate the undershoot the control would have to anticipate the temp falling below setpoint and preemptively stoke up. Remember, it is preemptively stoking down too. And you are trying to maintain temp setpoint as closely as possible, so you shouldn't me moving more than a degree off setpoint in either direction, which isn't a lot to base control decisions on without a high precision temperature reading and even with high precision you are stimied by the slow reaction time of the fuel, the unknown damping the stove body creates, and the unknown heat circulation charateristics of the house, the weather outside (wind, sun/cloud cover, etc. all play into heating response of the house), etc.

It is all a matter of compromises on responsiveness to fast changes vs tracking of long period changes vs limited information and ease of setup vs cost. We've got a number of ideas on how to improve things, but its taking longer than we had hoped to come up with a good solution.

Plus we're trying to run and grow a business, which isn't always all its cracked up to be.

I hear you Paul and I thank you for your responses. With the new max setting at 6/30 and the set temperature at 68 with room temperature at 70 I fired the stove up last night and she just went straight into idle never cranking the feed up at all. It was really nice the convection fan never kicked into high gear and she just stayed nice and quiet while taking the chill out of the air.