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Author Topic: boiler not going into high?  (Read 5769 times)

Bourboncask

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boiler not going into high?
« on: February 11, 2021, 10:51:08 AM »

Howdy gentlemen.  Question for any other 760 HDX owners out there.  I loaded my boiler up this morning and left for work.  had 3 or 4 pieces of wood in there from last night with a decent amount of coal bed.  Just noticed that the water temp took a nose dive after I loaded it and never recovered.  In looking at my FireStar log, it seems that the fan went from medium to low and never tried to ramp back up.  Just sat at low for 7 hours.  my wife sent me pictures of the reaction chamber and it's pretty full of ash (been lazy this last week during the cold snap).  I'm wondering if this furnace can tell there is a lack of air flow and not go to high mode?  I would think when the temp didn't recover after I loaded it up, eventually it would try to go to high.  I caught the water temp at 119 degrees, and I have the wife out there cleaning the ashes and keeping an eye on it until I can get home.  Any thoughts?

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Bourboncask

“The water was not fit to drink. To make it palatable, we had to add whisky. By diligent effort, I learned to like it.”  - Winston Churchill

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bjp

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Re: boiler not going into high?
« Reply #1 on: February 11, 2021, 01:50:47 PM »

A couple possibilities, based on my 750HD: a reaction chamber very full of ash can definitely do that, but when that happened to me it seemed more like a slow degradation (temps peaking at 1400F for a while, then over several loads barely hitting 1200F, then barely breaking 1000F), not a sudden drop off from high temps to low.  But if your peak temps in the last few days before this morning weren't well over 1000F that may have been the root cause.

One clarification as I understand it, the fan does not have a low/medium/high setting, the fan just has one speed and the stepper motors control how much airflow from the fan gets into the firebox and reaction chamber, so when firestar shows 'low' that's an indicator of reaction chamber temperature, not fan speed or airflow. I don't believe the furnace goes to high mode until it sees temperatures in the reaction chamber that convince it there is enough burning going on to open up the steppers to allow more airflow in.

Is there any chance you added some very wet wood or very large logs that weren't able to catch from the coal bed?

I had one, maybe two occasions last winter where I added wood and the fire went out, apparently due to low heat load from the house simply allowing the coals to cool.  I adjusted the pulse time in my settings to pulse a bit more frequently (20min, not 30min) and pulse to a higher temp (350, not 250) to keep that from happening again. It's a bit less efficient but it stopped that problem.

I would also suggest you pull the cover off the fan housing (with the controller turned off) so that you can inspect the elbows and steppers to make sure that they are actually opening as expected. If you're getting some creosote that stuck the lid to the elbow then the furnace can't provide enough airflow to get to high.  I'm kind of surprised that it sat in 'low' mode for 7 hours as my controller will report 'fire out' and shut down much sooner than that, I think somewhere around an hour or two of being unable to meet a call for heat.  It sounds to me like the fire just went out somehow, possibly from wet wood, or maybe leaving the bypass handle open (which would prevent high temps in the reaction chamber but still should have heated your water more than you're describing).

(Edit to add: I also had the stock fan die on me during the first winter, and the furnace looked like it was trying to run but could not get out of low since there was zero airflow.  But it should be very obvious to your or your wife's ears standing next to the boiler if the fan is simply not running.)
« Last Edit: February 11, 2021, 01:53:53 PM by bjp »
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Bourboncask

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Re: boiler not going into high?
« Reply #2 on: February 12, 2021, 05:42:14 AM »

Thanks bjp, after I got home and looked at it, it was probably a combination of larger chunks not properly dried and a pretty dirty reaction chamber.  Your right in the fact that its not a staged fan, but the addition of air that they are calling low, medium, high.  I misspoke. 

Just to clarify, after I loaded it at 4:30 am, the unit went into medium (water temp 178) and ran there until 6:23 (water temp 150).  So over the time of 2 hrs 50 min it was in medium and lost 28 degrees.  Then it switched to low mode at 6:23 am until 11:15 am.  At which point my water temp dropped from 150 to 118 degrees, and then I got alarms.  So, it was in low mode for 4 hours 40 min or so.  The 7 hrs I mentioned was a combination of medium and low modes.

My wonder yesterday was why it went from medium to low mode after I loaded it, and the temp was dropping.  I would think if it was trying to heat, and it was loosing ground, it would try harder, not let up.  I was confused by that.  Conventional wisdom would tell me that if it's loosing ground in medium mode, kick it up to high.  I looked threw the manual last night, and it's true that it's the reaction chamber temp that dictates how much air is introduced, when stepping up from low threw high.

From the manual:  In Demand Mode with the primary air actuator open, when the combustion temperature reaches 550˚F, the secondary air actuator will start to open and the Secondary status LED will be white. The secondary air actuator will continue to open more as the combustion temperature rises.

It's my first year with a boiler of any kind.  I didn't know I was going to get it until early August or so last summer.  It was installed October.  I didn't have much time to cut and dry wood.  I burn a fireplace inside, so I had some wood.  I had about 3 cord split and stacked.  I had another 4 cord bucked up and in a pile waiting to be split.  Once I found out I was getting the boiler, I started splitting and stacking as fast as I could. The long and the short of it is, I've been burning a combination of wood what is anywhere between 23% and 40% moisture.  My Idle pulse time is set at 15 min and my minimum idle pulse duration is at 50 min because of this.  Regardless, I've had it go out on my multiple times this year.  I'm chalking it up to a large learning curve. 

Thanks for taking the time to answer.  There is so much info in this forum.  I wish I had time to look threw all of it.

Bourbon





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Bourboncask

“The water was not fit to drink. To make it palatable, we had to add whisky. By diligent effort, I learned to like it.”  - Winston Churchill

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bjp

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Re: boiler not going into high?
« Reply #3 on: February 12, 2021, 06:08:05 AM »

Hi Bourbon,

With the additional info you gave there, I agree it has to be the wood moisture level. This is only my second season with the boiler, my first season I was only able to ready up 4 cords of lightly seasoned wood and another 8 of green; after my old (non-CB) boiler burned out in Feb 2019 I let my plow guy take my leftover wood in trade because he had some old widows who badly needed it and I had no use for it, as I wasn't sure if I would be replacing it. I ended up attempting to load mostly the dry wood with some green on top, but had pretty poor performance with it going out a few times. It gets a lot better next season when your wood is dry, a LOT better.

I've had the same thought about the way demand mode works and why doesn't it just try harder? I'm sure they have a good reason for it, but I haven't found it yet.

One thing that helped me last season (and I don't know if this would apply on the new 760HDX) was updating the firmware on the firestar controller. The firmware upgrade changed a few of the settings, but I think specifically it increased the default value for how far the primary air would open from I think 80% to 86%. Seems minor but it made a difference and I was down to mostly green wood by then. Your pulse time/duration settings sound exactly what I did to try to keep the fires from going out. I'd figure the 2020 models have the new firmware but it's still worth a check.

The one part that confuses me is this part from my controller manual -

FIRE OUT
When the system is calling for heat, if the temperature in the Reaction Chamber has been below 300˚F for 60 minutes and does not rise more than 5˚F, or after three hours even if the temperature is rising, the combustion fan will turn off and the primary air actuator will close. This alarm is reset by opening and closing the furnace door, or by turning the controller off and back on.


Maybe the 760HDX controller has some different programming, but the temps and durations you listed, I don't understand why the controller didn't decide the fire was out.

I'd also like to add that the 'account settings' link from your firestar page is VERY useful and can be used to set up email or text alerts when the boiler goes out, when the water temperature goes below some temp that you specify, and that works great for early notice of things like this.

Good luck, and it WILL get far easier with dry wood.
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Bourboncask

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Re: boiler not going into high?
« Reply #4 on: February 12, 2021, 07:57:14 AM »

I'm going to try and add a few pictures of my Dashboard graph.  You'll be able to see the water temp drop.  I've seen on my phone the dreaded "fire out", but it says that under the water and reaction chamber temp in the "easy re-fire / burn time" bar.  I had it there, but because I didn't have it set up to text me I didn't see it until way late in the game.  It wasn't listed in the alarms section of the time stamp either.  I just see the purple in the graph and that indicates an Alarm.  That occurred at 11:15 am.
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Bourboncask

“The water was not fit to drink. To make it palatable, we had to add whisky. By diligent effort, I learned to like it.”  - Winston Churchill

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A good back, and a bad ankle

Bourboncask

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Re: boiler not going into high?
« Reply #5 on: February 12, 2021, 07:58:17 AM »

Darn it, I'll never be able to figure out how to import a picture from my phone.   :bash:
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Bourboncask

“The water was not fit to drink. To make it palatable, we had to add whisky. By diligent effort, I learned to like it.”  - Winston Churchill

Stihl Farm Boss 290
Northstar 24 ton splitter
1980's ish M700 Bobcat
A good back, and a bad ankle

Pointblank

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Re: boiler not going into high?
« Reply #6 on: February 14, 2021, 07:37:54 PM »

It sounds like you might be fighting through some green firewood. These downdraft gasifiers run like a scalded dog on dry wood, but can struggle if the moisture content gets too high. You need a good coalbed to keep a good burn going and the greener the wood, the harder it is to maintain one.

It seems counter intuitive, but when the stove is in "low" mode, its actually trying its hardest to reignite the wood. All of the combustion air is forced into the firebox to get the fire relit. Its only when reaction chamber temps rise above 550 that the secondary damper opens and starts diverting some of the combustion air into the secondary chamber to help with the reburn. At least that's how it works in my older version of the Edge.
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Bourboncask

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Re: boiler not going into high?
« Reply #7 on: February 15, 2021, 10:07:42 AM »

Thanks, yes, I'm chalking it up to high moisture content. 

I can't wait until next year when I have decent wood to burn.  My brother has a 15 year old Classic and he throws huge chunks of oak in there he cut this summer.  That thing is amazing, how little has to be done to it to keep it going.  I'm getting all kinds of crap from him when he asks me how the boiler is running and I tell him I had to babysit it for 3 hours the other afternoon to keep it going.  In the long run though, I know I'll burn less wood heating more sq feet than he is.

Thanks all for your input. 
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Bourboncask

“The water was not fit to drink. To make it palatable, we had to add whisky. By diligent effort, I learned to like it.”  - Winston Churchill

Stihl Farm Boss 290
Northstar 24 ton splitter
1980's ish M700 Bobcat
A good back, and a bad ankle