2013 VC Burning Thread

[Reckless]

That sounds correct. If I understand it right the purpose of this control is to let more air into the cat chamber when the exhaust is cold, to aid light off and help it maintain cat temp. When its hot it closes down to limit the air supply. So seeing it close with the cat in the 1300+ range sounds right.

So when its cold its closed and when its hot (1300) its closed but when its really hot (1700) its open? This is what I see when I watch it through the burn cycle. My stove thinks it should let cold air into the chamber when the cat gets to hot and closes as it cools down again.

Reading into it I may need to do what this guy did or just close the secondary completely

Initially, I was asking the proper operation of the secondary air flap on the back of the stove. I was getting too hot, over-fire conditions, and could not control the burn temp. Up to and including 700 griddle temps almost all the time. This was frustrating, causing lack of sleep, etc.
I removed the 6x5 black cover on the rear of the stove, allowing me to view the operation of the secondary air flapper. When the stove would get hot the bi-metallic spring/lever would rotate from approx the 4 O-clock position to the 9 O-clock position. This was causing an opening of the secondary flapper, bringing in more air when Its hot.
I called my la VC dealer asking about the proper operation of this flapper. When I told him my idea of installing a stop screw to limit, He said "it sounds like you're on the right track.
So.......
Here are some pics of the fix.
Drilled and taped a 10-24 thread machine screw to limit the bi-metallic lever.
I also blocked off the EPA air holes on the bottom of the stove. Now I can regulate the burn! I can now achieve long night burn times, consistent temp range of 550-650, and the Northern lights effect instead of constant flame.
Sorry for the long post, I just wanted to share my fix!
I now love this stove, and I can sleep at night!
Thanks all for the advice!
I added magnets to the EPA holes on the bottom, and in

https://www.hearth.com/talk/threads...-the-primary-air-flap-supposed-to-work.60072/

 

[jharkin]

So when its cold its closed and when its hot (1300) its closed but when its really hot (1700) its open? This is what I see when I watch it through the burn cycle. My stove thinks it should let cold air into the chamber when the cat gets to hot and closes as it cools down again.

When its cold it should be open - that's why you set it at 4 o'clock on a cold stove which has the flap around 1/4" open or a bit more.
When the stove heats up it should progressively close.

That regulates cat temps by adding air when it cools off to help it burn more smoke, and restricting air when it heats up to slow down the burning.

I wonder if the guy in the link below is having his coil go all the way to 9 o'clock because he is already in overfire? I'll have to put a mirror back there and watch the position of mine from cold to 1700F and see what it does.

Reading into it I may need to do what this guy did or just close the secondary completely

https://www.hearth.com/talk/threads...-the-primary-air-flap-supposed-to-work.60072/

The limit stop is an interesting idea. Only thing I wonder is would the coil get distorted from hitting the stop all the time?[/quote]

 

[Reckless]

That would be great. I just took apart my old coil and new coil and swapped the parts and now my air flap is a 1/4 open at 4 oclock before it was closed. I also just re-gasketed the left door to be the full loop like you showed me now door to door passes dollar bill ... Time to load 3-4 splits of maple

Pics of coils look exactly the same....

 

[Reckless]

That would be great. I just took apart my old coil and new coil and swapped the parts and now my air flap is a 1/4 open at 4 oclock before it was closed. I also just re-gasketed the left door to be the full loop like you showed me now door to door passes dollar bill ... Time to load 3-4 splits of maple

Pics of coils look exactly the same....

k two hours in and I have way more control now. Griddle sitting at 550-600 and cat got as high as 1600 (but I made it go there to test) when I have the air 1/8th it sits pretty steady at 1400 with super soft slow flames and when I close all the way it shows nice secondary's and no back puffs.

What I have seen with the secondary air probe. Cold it is open 1/4" as the cat reaches 1350 its is open 1/4 all the way up to 15-1600 where I could now hear it sucking air and its maybe 3/8ths but it is maintaining its cat temps and never running away (where as before I fixed the door and secondary ap I would have been 1700s easy). I do believe that the secondary is to let cold air in when the stove starts to get too hot. When you had your stove apart where did that trap door lead to? From the looks it brings air in and around and up the flue to get the hot air moving out of the cat.... BUT I could be COMPLETELY wrong Wheres defiant when you need him

 

[jharkin]

The secondary air passes under the refractory box and then up between the refractory and the firebox (this preheats the air) to enter the cat hood and mix with the smoke entering the catalyst.

 

[Excavator]

Just installed my Conday digital monitor last night and I am very surprised how hot the CAT is when my pipe probe just above my T shows half the temp when cat is working. My cat was crusing along at 1200 and the probe just above the T was at 700. This explains why I was getting over firing so easy before I installed the cat probe.

 

[Reckless]

Just installed my Conday digital monitor last night and I am very surprised how hot the CAT is when my pipe probe just above my T shows half the temp when cat is working. My cat was crusing along at 1200 and the probe just above the T was at 700. This explains why I was getting over firing so easy before I installed the cat probe.

The pipe temp should drop once the cat is engaged and active and not being overfired, at least this is what I noticed. With damper open and griddle temp 450-500 flue temp 4-500 once damper is closed and cat active FT 2-300 every time. If your FT is over 4-500 your cat is probably up near 1700. Another thing Ive learned over the past week is GT is NO indication of cat temp. I have seen 300 GT and cat reading 14-1600! Cat probes are a necessity on this stove IMO.

 

[jharkin]

Yup, pipe temps will be hottest during bypass mode, and then drop quite low in cat operation. The cat probe is reading the hot exhaust 1/2" from te catalyst and then those gasses give up much of that heat to the back casting of the stove as they move down around and up before exiting. I have a flue surface thermometer 3 inches from the flue collar.... just because I had one lying around... and it will read surface pipe temps as low as 300 when the cat is cranking. This is how we get such high heating efficiency from the stove

 

[Excavator]

Yup, I will be saving wood and saving my stove now. I had to replace upper and lower fireback, refractory and cat last month from over fireing. now i know better

 

[jharkin]

I think my adjustments made a difference. Cruising on 4 med. Splits at under 1/4 air. 500 griddle, 1450 cat.



Then I closed the air down to 1/8 and the main flames died to almost nothing and cat temp settled down to 1400. Definitely more control than last time, and the draft is stronger at 29f out.

Edit: 4 hours later, outside temp up to 38, inside at 73, stove still over 400 but down to coals. Just reloaded a small 3 split load but may just let that one burn out as it will get to high 40s later. I think that removing the key damper from the horizontal run made a huge difference in draft as I got zero smoke top loading

 

[Reckless]

I think my adjustments made a difference. Cruising on 4 med. Splits at under 1/4 air. 500 griddle, 1450 cat.

View attachment 117163

Then I closed the air down to 1/8 and the main flames died to almost nothing and cat temp settled down to 1400. Definitely more control than last time, and the draft is stronger at 29f out.

Edit: 4 hours later, outside temp up to 38, inside at 73, stove still over 400 but down to coals. Just reloaded a small 3 split load but may just let that one burn out as it will get to high 40s later. I think that removing the key damper from the horizontal run made a huge difference in draft as I got zero smoke top loading

So it was running great for a few days.... stuffed it full of ash last night (loaded just below bypass) and 1.5 in cat is 1650 and griddle is climbing towards 700+. I loaded at 400 and it closed it down at the 10min mark, it took 30min for the cat to get to 900 I turned down the air a touch and it started climbing a touch more and the flames relaxed more but it kept climbing. Thank god I have the 8" flue pipe I went straight fireplace mode with the screen and it cooled down and burn up enough wood that I could close it up again and still had coals this morning. Im really frustrated now.

 

[Excavator]

we are still seeing a slow climb in temps after engaging cat at 350 and digital monitor shows 600 then climbs to 1000 in few minutes and i have to turn down air supply all the way. The gt will slowly climb as will the cat probe. Today twice it rose to 1800 with air shut down at 1000 degrees.
I might have to inspect my coil in back as well. This was just installed last month when i replaced complete fireback kit and cat along with new gaskets.

 

[jharkin]

So it was running great for a few days.... stuffed it full of ash last night (loaded just below bypass) and 1.5 in cat is 1650 and griddle is climbing towards 700+. I loaded at 400 and it closed it down at the 10min mark, it took 30min for the cat to get to 900 I turned down the air a touch and it started climbing a touch more and the flames relaxed more but it kept climbing. Thank god I have the 8" flue pipe I went straight fireplace mode with the screen and it cooled down and burn up enough wood that I could close it up again and still had coals this morning. Im really frustrated now.

You closed the bypass too soon. If it doesnt shoot to 1000+ in <5 min the cat is stalled. It can take as much as 20-30 min on a full load to get hot enough to close bypass.

 

[Reckless]

You closed the bypass too soon. If it doesnt shoot to 1000+ in <5 min the cat is stalled. It can take as much as 20-30 min on a full load to get hot enough to close bypass.

So if the cat is stalled and the longer it takes to become active the more wood reaches its gas off point before the cat is fully engaged SO by the time its engaged there is already too much gas for it to handle thus creating my over fire situation? It makes perfect sense and I will monitor this to see what happens. Thanks!

 

[jharkin]

So if the cat is stalled and the longer it takes to become active the more wood reaches its gas off point before the cat is fully engaged SO by the time its engaged there is already too much gas for it to handle thus creating my over fire situation? It makes perfect sense and I will monitor this to see what happens. Thanks!

I'm not sure about the overfiring, I just know that if it stalls at 800, usually reopening the bypass for another 5-10 minutes and then trying again usually produces better results for me than waiting it out.

 

[jharkin]

I think my adjustments made a difference. Cruising on 4 med. Splits at under 1/4 air. 500 griddle, 1450 cat.

Some more results to report. We had temps in the 30s with overnights down to the teens Tue and wednesday so I finally got to run some big loads. I am very happy with how the stove is operating.

• Tue @ 5pm - cold start with 4 med splits and I again got the cat to light off at only 450 griddle in about 20 min.
• Tue @ 9pm - refill to the top for overnight. I didn't really pack every cubic inch.
  • Overnight it dipped to the high teens but the living room stayed above 70.
• Wed @ 6:30am - still had coals and ~ 300F griddle. reload a 3/4 fill.
  • After letting it blast at 650 griddle/1200 cat for an hour to heat up the joint I lowered it for a low cruise.
  • The temps got to the high 30s so I didn't need any more wood until dinner
• Wed @ 5pm - just a few coals left and griddle down to around 225. I reloaded on the coals but it needs some coaxing to light off. Got a 1/2 load going
• Wed @ 10pm. Stove room still at 75 and predicted to hit 50s next day, I let it burn out.

What Ive noticed:

• I have not smelled or seen any smoke in the room while top loading. Even with the stove relatively cool.
• Stove has better control. Even with strong draft shutting the primary air kills the flame in the box almost completely as it should
• Catalytic temps are more reasonable and maintaining better. I haven't seen anything over 1500 yet, and as I change the primary air I am seeing the cat temps go up and down along with the griddle. i.e. if I have the air open 1/3 and the cat is at 1400 I can close it down to 1/8 and see the cat drop to 1250 or so.
• Cat lights off very easy. As soon as I get to 450 on the griddle, even if the cat probe reads cool, I can close the damper and the cat will light off in a couple minutes and go to 1100.
  
• Glass is staying cleaner. On the first few partial loads I didnt see the glass darken at all. On the first big low overnight loads the glass hazed over with a light brown coating in the usual crescent shape, stayed clean at the bottom edge near the coals and just had a couple black spots where split ends where too close. This might be as much due to better wood as the rebuild.
• The inside of the firebox has a uniform light brown ash coating everywhere. Old caked on creosote is burning off. In the past I would get brown on the fireback but black creosote around the doors and inside of the griddle. I attribute this to better wood and a hotter primary burn possible since i have better cat control.
• Its hard to say but I feel like I'm getting less ash leftover.

Overall I am feeling about the rebuild!

 

[Excavator]

Jharkin - Sounds like you got it right where you want it now!
I still can't believe how fast the cat temps climb from 350 to 1100 or higher after closing the damper.
I am getting more use to it now and by biggest problem is my dry wood and if I keep bigger splits and cut down air supply sooner I can keep it from getting too hot. All these years I burnt this stove with just griddle thermometer and I see now why I had to rebuild the stove. I was burning it too hot.

 

[fortuna1]

I'm new to cat stoves, but man, I cannot imagine running this stove and not having the condar catalyst temp monitor. So easy to overfire!

 

[Excavator]

Just inspected my secondary flap and found it to be 3/8 open at cold! I adjusted it and now have 1/4 gap cold and tonight when colder I will experiment and see if secondarys behave better. I am hoping to see better control of the secondary from running too hot once cat was lit.

 

[Reckless]

Just inspected my secondary flap and found it to be 3/8 open at cold! I adjusted it and now have 1/4 gap cold and tonight when colder I will experiment and see if secondarys behave better. I am hoping to see better control of the secondary from running too hot once cat was lit.

Do you mean a 1/4 open resting on the stopper that keeps it from closing or 1/4 open from there? I keep debating if I should turn the probe from 4 to 6 o'clock and see if there is a difference with control.

 

[Excavator]

I used 1/4 inch drill bit and have the gap from the flapper to the spot that the flapper would be if closed. It was 3/8 and I think that was my problem.
I tried 6 oclock but then went to 5 oclock and that worked best. Tonight will be test

 

[Excavator]

So I did my test last night and kept the cover off the coil to watch the results. At start up the flapper was open 1/4 and as stove hit griddle temp of 350 I closed bypass and cat probe showed cool for 2 minutes then quickly climbed to 1100 and then I slowly closed air supply and noticed the flapper now closed. Cat probe very slowly climbed and after few minutes I had air supply closed all the way. After another 20 minutes I could see flames getting bigger so I checked flapper. The flapper now started to open again and cat probe showed 1650 - 1750. As the flapper stayed open I could hear the stove roar a little louder but never got out of control. When I woke up 5 hours later the griddle temp was at 450 and cat probe was also 450 and warm in house. So I guess that the flapper does open back up when getting too hot too let cool air in but I was skeptical of that idea.
I am thinking of turning the coil to 3 oclock position when cold and see if that stops the coil from opening the flapper so much when it reaches 1600 on cat probe. Right now stove is cruising at 650 GT and 1700 cat probe with air all the way down and the coil is at 8 o clock position.

 

[Reckless]

So I did my test last night and kept the cover off the coil to watch the results. At start up the flapper was open 1/4 and as stove hit griddle temp of 350 I closed bypass and cat probe showed cool for 2 minutes then quickly climbed to 1100 and then I slowly closed air supply and noticed the flapper now closed. Cat probe very slowly climbed and after few minutes I had air supply closed all the way. After another 20 minutes I could see flames getting bigger so I checked flapper. The flapper now started to open again and cat probe showed 1650 - 1750. As the flapper stayed open I could hear the stove roar a little louder but never got out of control. When I woke up 5 hours later the griddle temp was at 450 and cat probe was also 450 and warm in house. So I guess that the flapper does open back up when getting too hot too let cool air in but I was skeptical of that idea.
I am thinking of turning the coil to 3 oclock position when cold and see if that stops the coil from opening the flapper so much when it reaches 1600 on cat probe. Right now stove is cruising at 650 GT and 1700 cat probe with air all the way down and the coil is at 8 o clock position.

1650-1750??? I would have been a little worried as the ceramic cats printed limit is 1700, what was your GT at that point?

 

[Excavator]

grill temp was 600. I have since stated cutting air down even sooner and i am having better results. When I engauge cat at 350 on cat probe and cut air down to 1/2 the cat still climbs fast and when cat probe hits 950 i cut air down to 1/4 and all seems well. Cat probe will see 1400 but stays or decreases from then on

 

[jharkin]

Guys I still don't see the secondary air inlet as doing anything to cool the cat, the air is preheated and feeds the cat inlet. I firmly believe its function is to add oxygen to help burn the large volume of smoke when the cat is very hot.


Anyway, yeah its possible to hit crazy temps if you are not careful. I had my first scare, cat stalled at 850, so I open the air to half and come back 5 min later hearing the roar and see 1850! Aaaaaaaaaaaaaaaa

Open the bypass and let it cool then reengage at 1400 and low air and it stabilized. Couldn't have been more than 5 min hope I didn't do major damage.

Btw, that trick works every time...

If you overheat:
Open bypass
Air to minimum
Wait for cat probe to drop down to 1200
Close bypass

It will reengage and lock in at a safe temp.