New Classic Edge owner, looking for help with firestar settings/burning efficiently

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ThatDonkeyLooksCold

New Member
Jan 28, 2022
6
Houston, BC
Hi everyone, new to the forum and to wood boilers in general. My wife and I moved onto an acreage last summer that had nothing but electric heat in all the buildings. We installed a Central Boiler classic edge 360HDX this fall, and got it fired up in the first week of December. We're heating two buildings- our 1700 sq ft house via a forced air heat exchanger, and our small (4-500 sq ft) cabin, with the CB fan convector (part # 1971).

I'm burning mostly pine and spruce as that is what makes up most of the firewood around my area (Northern BC). Ideally I'd burn hardwood but it's hard to get around here. It's definitely dry as it all reads below 20% on my moisture meter, most of it around 12-14%.

When I first started the boiler, I left the settings as factory: 185F setpoint, 20 deg temp differential, 30 min idle pulse timeout, 225F target pulse temp. I found it almost impossible to keep a fire going, I would get one good burn, and then the fire would go out the next time there was a call for heat. I called CB and discussed settings with them, they recommended a 15 deg temp differential, 20 min pulse timeout, and 260F target temperature. Even with these settings, the fire would still go out every few days.

I've been playing with the settings ever since, and initially set it for 185 set/ 15 differential/ 10 min timeout/ 310 pulse temp. Extreme, I know, but it's the only way I could get it to run. Now I've gotten it down to a 15 min timeout and 300 pulse temp, and it mostly does ok, but still goes out once every week or two and I have to watch it like a hawk.

This was fine when the weather was colder (we had almost a month of 0F to -35F weather, but now that it's warmed up to around 30F, my pulses are so close together that the water is getting close to overheating in the afternoon when the sun is out and warming my buildings.

I played around with it a bit tonight when I got home from work- I pulled both air delivery elbows off and made sure neither are plugged up at all. I also checked the firestar software version number and it is up to date. I set it back to a 10 deg differential, 20 min pulse, and 260F target temp. It got through two burns and then was about to go out, dropping to 7% and 155F. I pulled all the wood out and found 3-4" of coals, but they weren't lit at all, and the charge air tube was not obstructed. I closed the door for 2 minutes and when I opened it back up I had a glowing hot coal bed. I just loaded the wood back in and returned to my 15 pulse/300 target temp settings as I'm about to head to bed.

I've never seen a reaction chamber temperature over 1000, usually in the 800s even after it's been at 100% for 10+ minutes. My coal bed is always at least a couple inches deep, and when the boiler does go out, there's still tons of coals underneath the unburnt wood.

The previous owners did leave a bunch of dry, split birch in a firewood shed that measured at 12%, so I tried that for a while but it didn't seem to make much difference. Neither did burning some reject 2x6 that i had lying around. Obviously I'm burning more wood than I'd like with such extreme pulse settings, but I don't seem to have much choice. I've been cleaning the reaction chamber and heat exchangers every week, and the firebox once a month.

Lastly, the firestar manual says that the "Burn Time Monitor" will accumulate whenever the fan is running, but my burn time monitor only goes up when the furnace is in demand mode, and not during pulses, which can be 8-10 minute sometimes.

Any input or suggestions would be greatly appreciated! Thank you
 
Another thing I forgot to mention, when the furnace is at 100% and reaction chamber is around 850, I'm still seeing a decent amount of smoke out of the chimney.... nothing like the CB videos that show a smoke-free stack
 
No experience with that boiler but thinking part of the issues might be your wood. Its super dry and fast burning (sounds like), so the boiler might not be able to handle and burn all the off gassing from it. Leading to cooler gassing temps and the smoke. Also dry soft wood isnt conducive to good coaling. Have you tried smaller fires to see what that does?
 
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No experience with that boiler but thinking part of the issues might be your wood. Its super dry and fast burning (sounds like), so the boiler might not be able to handle and burn all the off gassing from it. Leading to cooler gassing temps and the smoke. Also dry soft wood isnt conducive to good coaling. Have you tried smaller fires to see what that does?

I guess there could be some sense to that. I've tried burning various types of wood with similar results every time though. I always have a couple inches of coals, so I don't think a coalbed is my issue. I have tried smaller fires, but it's basically the same thing for a shorter period of time.

It almost did it to me again just now- I'm still at work but keeping an eye on it and here's what the last 8 hours have looked like for me. You can see where I put wood in it on the far left (purple bar). I then had 4 good burns at 100%, then one that started to drop off before it got to setpoint, and then this last one that's just ramping up after almost going out.

BoilerJan29.jpg
 
If it is not getting over 1000*F in the lower chamber, it is not burning right at all...gasification burn is just getting started at about 1000* or so....I think it goes almost double that when things are rolling good.
I know HeatMaster says to not run much more than 10-15% pine in any given load...it just off gasses too fast/hard...overwhelms the burn chamber in fuel (rich mixture)
Does CB allow you to tweak the primary/secondary air settings?
 
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If it is not getting over 1000*F in the lower chamber, it is not burning right at all...gasification burn is just getting started at about 1000* or so....I think it goes almost double that when things are rolling good.
I know HeatMaster says to not run much more than 10-15% pine in any given load...it just off gasses too fast/hard...overwhelms the burn chamber in fuel (rich mixture)
Does CB allow you to tweak the primary/secondary air settings?
Thanks, it's definitely not burning right and it seems to be an air delivery problem.

I woke up to my alarm last night at 3:45 am that the fire was out, so I went and had a look. Pushed the ignition air button, checked my primary and secondary actuators and they didn't seem to be open at all. I powered the furnace off and back on, and did a self-test on the firestar controller, both actuators opened fully. I did a factory reset to the controller, powered it off and back on again for now. I've been keeping an eye on the actuators over the last 20 hours and they don't seem to be opening well at all.

Another issue I have is my controller isn't counting burn time when the fan is running in pulse mode, which makes no sense. Nothing I do seems to fix that issue either.... this is another reason I'm leaning towards this being a controller issue.
 
Thanks, it's definitely not burning right and it seems to be an air delivery problem.

I woke up to my alarm last night at 3:45 am that the fire was out, so I went and had a look. Pushed the ignition air button, checked my primary and secondary actuators and they didn't seem to be open at all. I powered the furnace off and back on, and did a self-test on the firestar controller, both actuators opened fully. I did a factory reset to the controller, powered it off and back on again for now. I've been keeping an eye on the actuators over the last 20 hours and they don't seem to be opening well at all.

Another issue I have is my controller isn't counting burn time when the fan is running in pulse mode, which makes no sense. Nothing I do seems to fix that issue either.... this is another reason I'm leaning towards this being a controller issue.
Let's address this one issue at a time, as there is more than likely a few things going on here.

Fire dying between burns is either the issue of settings in the FireStar controller or boiler's primary air inlets are plugged up with creosote. Primary air is delivered through small round holes (about 3/4in diameter) in side air channels located inside the fire box, bottom left and right, and front air channel located directly below the firebox door opening. Charge tube doesn't have anything to do with primary air delivery to the fire box. First thing to check is that all those little holes are not completely plugged up with creosote and there is air coming out of them when a pulse is on or boiler is in the middle of a burn cycle.

On to FireStar settings. The amount of air delivered to the fire box during pulse is controlled by Primary Air High Percent setting. That should be somewhere around 30%. Set your temperature spread so that the boiler goes into a burn cycle every ~2 hours or so. Don't have it sit idle for extra long periods of time. If you need to drop the temperature differential to 5 degrees because it's warm outside and there is no heat load, that's just fine. For reference, I run my 550 at set temperature of 185F, 10 degree spread, 35 minute between pulses, 40 seconds minimum pulse (make sure this is not set to something stupid low), 225F minimum temp. Burning pine just like you, works fine. Mind you I have a massive heat load, on account of sh**y underground piping. Trying to warm planet Earth here.

Let's start there. There are obviously other issues. You are not achieving gasification and if this has been going on for a while your heat exchanger is probably completely plugged up with creosote.
 
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Let's address this one issue at a time, as there is more than likely a few things going on here.

Fire dying between burns is either the issue of settings in the FireStar controller or boiler's primary air inlets are plugged up with creosote. Primary air is delivered through small round holes (about 3/4in diameter) in side air channels located inside the fire box, bottom left and right, and front air channel located directly below the firebox door opening. Charge tube doesn't have anything to do with primary air delivery to the fire box. First thing to check is that all those little holes are not completely plugged up with creosote and there is air coming out of them when a pulse is on or boiler is in the middle of a burn cycle.

On to FireStar settings. The amount of air delivered to the fire box during pulse is controlled by Primary Air High Percent setting. That should be somewhere around 30%. Set your temperature spread so that the boiler goes into a burn cycle every ~2 hours or so. Don't have it sit idle for extra long periods of time. If you need to drop the temperature differential to 5 degrees because it's warm outside and there is no heat load, that's just fine. For reference, I run my 550 at set temperature of 185F, 10 degree spread, 35 minute between pulses, 40 seconds minimum pulse (make sure this is not set to something stupid low), 225F minimum temp. Burning pine just like you, works fine. Mind you I have a massive heat load, on account of sh**y underground piping. Trying to warm planet Earth here.

Let's start there. There are obviously other issues. You are not achieving gasification and if this has been going on for a while your heat exchanger is probably completely plugged up with creosote.

I do not have a creosote issue. I have had both air tubes out and verified they are clear, as well as the plate on the inside front of the boiler. There is little to no creosote built up in either the primary or secondary elbows as well.

I have the newer Firestar 6.8 which doesn't have a "primary air high percent" option. Basically I can set time between pulses, minimum pulse time and target pulse temperature and that's it. Obviously I can also adjust setpoint and temperature spread as well. I definitely have been moving down to a 10 degree temp spread now that the weather is getting warmer.

I have been in contact with Central Boiler, and they are fairly convinced I have a software or hardware issue. I'll know by tomorrow if they're going to send me a new controller, primary stepper, or both.

They have me checking my stepper motors in each "demand" cycle, and I caught it a couple days ago stalled out with the reaction chamber at 38% and not climbing. When I checked my steppers, both primary and secondary were basically shut and only open millimeters at best. I'll let you know what CB decides to do with it

Thanks for the reply!
 
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I do not have a creosote issue. I have had both air tubes out and verified they are clear, as well as the plate on the inside front of the boiler. There is little to no creosote built up in either the primary or secondary elbows as well.

I have the newer Firestar 6.8 which doesn't have a "primary air high percent" option. Basically I can set time between pulses, minimum pulse time and target pulse temperature and that's it. Obviously I can also adjust setpoint and temperature spread as well. I definitely have been moving down to a 10 degree temp spread now that the weather is getting warmer.

I have been in contact with Central Boiler, and they are fairly convinced I have a software or hardware issue. I'll know by tomorrow if they're going to send me a new controller, primary stepper, or both.

They have me checking my stepper motors in each "demand" cycle, and I caught it a couple days ago stalled out with the reaction chamber at 38% and not climbing. When I checked my steppers, both primary and secondary were basically shut and only open millimeters at best. I'll let you know what CB decides to do with it

Thanks for the reply!

Right your are. Looks like Central Boiler has completely eliminated control over primary/secondary air amounts from the software interface. I sure hope that they wrote an algorithm that continuously adjusts air supply and didn't just plug a couple of numbers in there that they think work most of the time and call it a day. I'm not even convinced that you can write an effective algorithm based on a single thermocouple temperature read out.

For what it's worth, the air gap on the primary/secondary air elbows is pretty small even when they are fully open. Maybe around 1/4in at wide open and they are never open that wide. As you can imagine, at say 20% open, it will be a very small gap.

Their new default settings are bat chit crazy, too. At 20F temperature spread, that fire will be going out all the time, unless there is a massive heat load. A coal bed will have trouble re-igniting if temperature at the thermocouple reads much below 225F. So if you get a pulse when temperature reads, for example 230F, controller say 'everything is good', pump in air for 50 seconds and shuts down for another 1/2 hour. Thing is, with a pine coal bed, that pulse has made pretty much no difference to the temperature of the coals. By the time the next pulse comes around, temperature might read 200F, the coal bed is proper dead and no amount of air will re-ignite it.

What's this new Reaction Chamber % reading supposed to represent?
 
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Right your are. Looks like Central Boiler has completely eliminated control over primary/secondary air amounts from the software interface. I sure hope that they wrote an algorithm that continuously adjusts air supply and didn't just plug a couple of numbers in there that they think work most of the time and call it a day. I'm not even convinced that you can write an effective algorithm based on a single thermocouple temperature read out.
Do the CB's use any kind of O2 sensor at all ?
 
They did release an updated HDX series in 2019 but changes were pretty minor. I don't believe there is an O2 sensor in there, either.
Heatmaster is the only OWB company that I'm aware of that's putting a O2 sensor in their boilers.

I wonder why more of these companies are not going that route. They've been in the European boilers ( lambda functionality ) for years. Like you said, maybe the correct algorithms are hard to code for using a O2 sensor so that's why they are sticking with a basic thermocouple.
 
Heatmaster is the only OWB company that I'm aware of that's putting a O2 sensor in their boilers.

I wonder why more of these companies are not going that route. They've been in the European boilers ( lambda functionality ) for years. Like you said, maybe the correct algorithms are hard to code for using a O2 sensor so that's why they are sticking with a basic thermocouple.
I would say building the best products is seldom "easy"...but still worth it in most cases...gotta give HM an atta-boy for doing the hard work here...I know my folks are still enjoying theirs.