Can't Keep Heco 520 Cool

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mattie5960

New Member
Mar 28, 2022
31
PA, USA
Hello,

Bought my first wood stove and went straight for the biggest and baddest, or thereabouts.

Trying to heat a 3000sqft home, built in late 1800s with some remodeling and additions in the last 50 years. Flue is 25 or 30 feet straight up through chimney (lined pipe through chimney).

My issue is that this thing has a large firebox, and an overheat surface temperature of 800 according the the manual. However, with a hot bed of coals and only two logs, the secondary air will let it get up over 800. I can choke off the secondary air to cool it down, but then it's smoking out the stack.

The other day I really loaded it up and the surface temperature got so hot it burned the paint off my thermometer. Judging by where the needle went, it must've been 1200 or 1300. Despite this, the thermometer I have on the stove pipe was only at 450 at this time. The stove pipe sits at around 250 if the stove top is around 700 or 800. No parts of the stove were glowing red or anything, but I'm just not sure what to think. The thing wants to run hot.

So what am I supposed to do? Only throw a couple logs in at a time and keep refueling it every 90 minutes or so?

Edit: I should add that all these temps are with the primary air closed off. When the wood is gassing, it'll just rip and rip and rip.
 
Last edited:

kennyp2339

Minister of Fire
Feb 16, 2014
6,541
07462
Please mind my ignorance here, but your referring to a wood / coal cookstove?
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
Please mind my ignorance here, but your referring to a wood / coal cookstove?
Yes. Burning wood. Measuring <10% moisture. As we speak, I'm about 10 minutes after putting two fresh logs on top of coals and the remains of two degassed logs. Firebox is maybe 50% full, at most. The primary is closed, the secondary is at like 60% open, and the stove top is pushing 1000.

I just closed the secondary down to 10% to cool it down, but based on the archive of info here, it seems like this kind of heat is abnormal at best and bad for the stove, at worst.

Edit: Even with the secondary closed down to 10% for a few minutes, stove top is still getting hotter. Close to 1100 now, I'd estimate. Little bit of smoke out of the stack at the moment, but not bad. Stove pipe at only 275 or so.
 
Last edited:

begreen

Mooderator
Staff member
Nov 18, 2005
93,242
South Puget Sound, WA
When burning wood, the primary air should be closed off except on startup. That puts air under the fire for coal burning. Regulate the fire with the secondary (airwash) air. Try closing down the secondary air sooner and try thicker splits. If the <10% wood moisture is being tested after resplitting the wood and then testing on the freshly exposed inside face of the wood, then the firewood is exceptionally dry. Try mixing in wood that is ~17% moisture for better control.
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
28,474
central pa
Hello,

Bought my first wood stove and went straight for the biggest and baddest, or thereabouts.

Trying to heat a 3000sqft home, built in late 1800s with some remodeling and additions in the last 50 years. Flue is 25 or 30 feet straight up through chimney (lined pipe through chimney).

My issue is that this thing has a large firebox, and an overheat surface temperature of 800 according the the manual. However, with a hot bed of coals and only two logs, the secondary air will let it get up over 800. I can choke off the secondary air to cool it down, but then it's smoking out the stack.

The other day I really loaded it up and the surface temperature got so hot it burned the paint off my thermometer. Judging by where the needle went, it must've been 1200 or 1300. Despite this, the thermometer I have on the stove pipe was only at 450 at this time. The stove pipe sits at around 250 if the stove top is around 700 or 800. No parts of the stove were glowing red or anything, but I'm just not sure what to think. The thing wants to run hot.

So what am I supposed to do? Only throw a couple logs in at a time and keep refueling it every 90 minutes or so?

Edit: I should add that all these temps are with the primary air closed off. When the wood is gassing, it'll just rip and rip and rip.
Do you have a damper on the pipe? I couldn't find a manual for your stove. Is there a conversion to use it with wood or is it sti using coal grates and feeding air from under the wood?
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
Firebox, stove top, and stove pipe pictures attached.
20220328_121811.jpg
20220328_121828.jpg

20220328_121833.jpg
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
When burning wood, the primary air should be closed off except on startup. That puts air under the fire for coal burning. Regulate the fire with the secondary (airwash) air. Try closing down the secondary air sooner and try thicker splits. If the <10% wood moisture is being tested after resplitting the wood and then testing on the freshly exposed inside face of the wood, then the firewood is exceptionally dry. Try mixing in wood that is ~17% moisture for better control.
Yes, these readings are after resplitting the wood. Some if it has been as low as 4% to 5% moisture.

My concern with closing down the secondary is that the wood is basically evaporating without burning at that point, which makes for a smokey stack.
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
Do you have a damper on the pipe? I couldn't find a manual for your stove. Is there a conversion to use it with wood or is it sti using coal grates and feeding air from under the wood?
No damper on the pipe, but the stove does have a wood burning conversion plate that's covering the grates.
 

Hoytman

Feeling the Heat
Jan 6, 2020
386
Ohio
Should have came with a wood burning plate.

Two things I noticed you said....
1. Near the bottom of your post you said the primary air was shut down, or something to that effect.

2. Choking off the secondary air to cool it down will cause it to smoke...that’s given. Now it has no air and is smoldering.

Makes sense to try closing primary air much more soon and not allowing it to get so hot before letting secondary air take over...which will typically run hot anyway.

I doubt if you hurt the stove, but you probably seasoned the paint real well.

I thought I had a copy of the manual or at least a link to it, but I can’t seem to locate it.

 

Hoytman

Feeling the Heat
Jan 6, 2020
386
Ohio
By the way...that’s a D.S. Stove...father and son outfit if my memory serves me. One runs DS the other Heco...Heco came from DS I believe.

By the way, with it without a damper in pipe...BHoller’s suggestion is correct...

...there is really no reason to load that stove up until you learn how to control it. Sort of keeps the stress level down.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,242
South Puget Sound, WA
Do you have a damper on the pipe? I couldn't find a manual for your stove. Is there a conversion to use it with wood or is it sti using coal grates and feeding air from under the wood?
The primary air is under the grates (coal bed) and is thermostatically controlled at the user setting. The airwash is what they call "secondary air" but is actually the primary air for wood burning in the stove. One thing is to make sure the ashpan door is sealing tightly.

Note that the manual says no to the pipe damper for wood burning:

17. Do not use a manual, barometric or automatic damper when burning wood.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
93,242
South Puget Sound, WA
By the way...that’s a D.S. Stove...father and son outfit if my memory serves me. One runs DS the other Heco...Heco came from DS I believe.

By the way, with it without a damper in pipe...BHoller’s suggestion is correct...

...there is really no reason to load that stove up until you learn how to control it. Sort of keeps the stress level down.
I think DS purchased Heco during the pandemic, a couple years ago.
 
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mattie5960

New Member
Mar 28, 2022
31
PA, USA
@begreen The ash pan door is sealing well. Thanks for the comment on not installing a pipe damper, per the manual.

I suppose the move is to get it off the thermostatic primary as soon as I have a good flame and see how that does. I've been keeping the primary set to 60% to 80% (lower when starting, then turn it up once the stove is hot), but that obviously seems to be too much. I like to leave it set at 80% or so overnight because the thermostatic controller opens the primary air flap as the coals burn down overnight, so I wake up to ash dust and a few coals instead of a bunch of charred chunks.

Stovetop is at 680 right now with thermostatic primary set to 80%, and the air flap is fully closed. It will probably start to open up again when the temp drops another 100 degrees or so.

Next time I load it up I'll turn down the primary until the flap is closed again and let the secondary do it's thing. We'll see what the temps get to then. Seems a bit annoying to have to climb behind the stove to twist the thermostatic primary knob every time I add wood, but if the stove is getting super hot too fast for the Thermostat to react and close the primary air flap, I guess some manual intervention is the only way to control it.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,242
South Puget Sound, WA
You might be able to leave the thermostatic air always off. Start fires with the secondary airwash air wide open. Given the dryness of the wood, try starting with the thermostatic air off all the time, even for starting. You can open the firebox door for a little extra air at start. Turn down the secondary airwash air once as the flames get stronger.
 

SpaceBus

Minister of Fire
Nov 18, 2018
6,885
Downeast Maine
I have a different cookstove, but it also has under fire "primary" air, a "secondary" air slider over the glass, and an unregulated manifold in the back. I only use the under fire air control when lighting a cold stove, and I close it as soon as I can without killing the fire. When there are good "live" coals and the stove is hot I just add more wood, and keep the under fire air control 0% open. I regulate firebox temp with the air wash slider and generally leave it open unless I'm reloading on hot coals and need to keep the oven from getting any hotter. My stove is a bit smaller than the Heco and has a fixed slotted grate instead of the shakers. During a windstorm I was trying to burn down some coals and left the under fire air open a little too long and my appliance connector started smoking. I got it calmed down, but it was a bit spooky. The Heco stoves are really designed to burn coal, wood is more of an afterthought.
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
Quick update. My issue seems to generally have been too much wood.

My novice thought process was:
As much wood as I want to put in
+ set the air to a controlled burn
= a slow fire that lasts hours and hours and hours

In reality, the wood (of any quantity) is going to basically evaporate at whatever rate it's going to evaporate at. Choking off a bunch of wood will do nothing but create a super smokey "fire". Or else, I give it more air and find myself counting the number of times the thermometer needle has gone around the gauge. This was exacerbated by the thermostatic primary air control lagging the temperature of the stove enough that by the time it closed the air flap, the stove was already very very hot.

With a hot bed of coals, I can throw one big log in, or two little logs, and it stays under 800. If it gets cool to the point that the thermostatic primary air flap has opened up, I close that before adding wood. Then I can turn it back up after the stove has settled in around 700 or so. I just set the secondary air control to whatever seems to let the fresh log burn without smoke and leave it.
 
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SpaceBus

Minister of Fire
Nov 18, 2018
6,885
Downeast Maine
It sounds like your draft is very strong, and that's part of the challenge you are facing. I think if you get the air turned down fast and early, especially that under fire air, you will be doing much better. I struggled to control my cookstove at first as well. It's a learning curve and you will get it much faster burning smaller fires, like you said.
 
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mattie5960

New Member
Mar 28, 2022
31
PA, USA
Haven't been using the thermostatic air since yesterday around noon. Still finding it difficult to keep the stove temp down. I had it hit 900 a couple hours ago with only 2 fresh splits and one that had already been blackened, plus the embers. I think my error there was throwing the fresh splits in while the stove was still around 550 or 600 (even though it was just the one charred split and embers that were sustaining that heat). With it that warm already, I didn't have time to get the new splits charred enough to turn the secondary air back before the stove top temp was getting over 800.

It's back down to 500 or so now with just embers left. I'll let it cool to 300 or so before I try it again and see if I can get a few logs in there, started, and then choked back on the secondary without it getting over 800 again.
 
Last edited:

SpaceBus

Minister of Fire
Nov 18, 2018
6,885
Downeast Maine
I still suspect you have very strong draft if all this is happening with the oven engaged. Is there a manual-approved way to reduce draft?
 

mattie5960

New Member
Mar 28, 2022
31
PA, USA
I still suspect you have very strong draft if all this is happening with the oven engaged. Is there a manual-approved way to reduce draft?
What do you mean by "with the oven engaged"?

I don't have the oven engaged. The manual says to leave it disengaged unless you're actually cooking something in the oven.

I'll have to check the manual again to see if it says anything about draft control. I suspect I'm just supposed to keep backing off the secondary air to counteract the draft. The intake holes do have an audible "whirr" when the stove is hot and they're sucking air in, though.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
28,474
central pa
What do you mean by "with the oven engaged"?

I don't have the oven engaged. The manual says to leave it disengaged unless you're actually cooking something in the oven.

I'll have to check the manual again to see if it says anything about draft control. I suspect I'm just supposed to keep backing off the secondary air to counteract the draft. The intake holes do have an audible "whirr" when the stove is hot and they're sucking air in, though.
What are your pipe temps when the stove is that hot?