Do I have too much draft?

[cabinwarmer]

Good Day. I am having a tough time backing down a fuller load of splits in my new GM 60. This has happened several times:

1) Several hours of burning thru the day, adding just two splits at a time, 1/4 intake open mostly. All good. Flue temp 400-500. Perfect.
2) Once I leave the wood die down to red coals and add more then two splits, the flue temp rises.
3) I then try to back it off by closing the intake all the way. Slowly but steady the flue temp rises a few degrees at a time. Example - from 375 - up to 500. Non stop.
4) I then grabbed the tin foil ball and stuffed up the intake. The stove is now running at 470 with a nice secondary burn Holding study.

I have waited different amount of times before adding the larger load (low coals, hot coals, ext.).Happens consistently. I am trying to get to an overnight burnout this is stopping me. I believe there should be more control over the flue temp then what I am getting.

Do I need a flue damper? Will that help or hurt?

There is ~10 feet from the top of stove to the cathedral ceiling box - 6 inch DVL. Another ~10 feet of outside stainless pipe. Total of ~20 feet straight up.

Thanks for the feedback, Appreciate your thoughts,

Dave

 

[jetsam]

20'straight up may well need a damper. I'd get a damper and a manometer if I were you- the manometer can help you adjust the damper correctly.

Someone familiar with the stove may have more specific info, but 20' is not the longest run out there but could be enough to draft like crazy in cold weather.

 

[begreen]

I doubt a damper is necessary and a 500º flue temp is nothing to get worked up about unless that is a surface reading on single-wall stove pipe. Our flue system is also 20' and it's just about perfect. I am assuming you are closing the bypass to engage the cat, right? What does the catalyst thermometer read?

The only way an overnight burn is going to be achieved is with enough fuel to last 8-10 hrs. That will require a full load in this size stove.

 

[cabinwarmer]

Thanks for your response guys. Jetsam, It has been around 40F most of the time around here. Cool but not cold. Draft is strong during normal operation. I run the intake at 1/8 during the day and the flue stays between 450-475F. Begreen, yes the cat had been engaged. The issue happens when reloading more then two 3-4 inch splits. I do not have a digital cat reading, just an analog gauge on the side of the stove from the manufacturer. I would say it was around 700-750F if I had to guess from the gauge. It ranges from 500-1000F from what I have read. Understand the amount of wood required, that is the issue. I know 500 is not hot, my concern is not the temp, but the total lack of control to back it down when reloading the additional splits. I am reloading only on a bed of red coals. If I wait longer, the new splits would not catch. Does that help?

 

[moresnow]

Your cat is reacting to the continually added splits. Its a GM60 Cat stove, correct? Why are you reloading more than once every 10-12 hrs at very most? It's a cat stove rated to burn 24hrs. Burn in batch's. One load runs until burned down to very, very little without fussing with it. Then open the door for a reload. Cat stove's operate a little differently and aren't really setup for constant tending. Constant loading door opening on a hot cat equipped stove is rather well understood to possibly cause thermal shock to the Catalsyt from the entry of cool room air. Diminishing it's lifespan. How does your manual say to run the stove? Just a few thoughts/considerations from a Cat stove owner. Really looking forward to some feedback on these stove's.

 

[cabinwarmer]

Moresnow, yes it is a new GM 60 CAT stove. It is my first CAT stove as well. I have been reloading every few hours with two 4 inch splits, bringing flue temp up and then backing down the intact, all good. Are you saying to add more then just the two splits? When I do that, I get the lack of control over the increased flue temp. OR, will it settle down after a certain time? Sounds like my two split add is not the way to go? I just re-read the manual and it is not totally clear on reloading, but I believe I have been following the directions. As far as opening the door during burning, the manufacturer instructs to close the bypass, which I have done, then open and reactivate the cat after loaded. Your feedback seems to be right on. Any further comments are very much welcome.

 

[kennyp2339]

Take advantage of today, it cool and rainy - load that stove up let the load catch then turn the air down some and let the stove do it job. use +5 pieces or load to the top of the fire bricks.
Its a hybrid stove so you have secondary air tubes and a cat combuster, the cat in this stove is designed to be the last of the scrubbing for clean burns, not necessarily for addition performance (like other cat stoves) internal stove temps need to be above 1000 deg f for the secondary re-burn to occur and it should be a little more violent then lazy cat stove flames.

 

[cabinwarmer]

kennyp2339 - thanks for the detail, this is helpful as well as the other posts. Understood on the secondary burn, I do achieve that when flue temp gets to ~425F, and it does dance nicely as you described. What flue temps would you expect to see on this model stove?
(nervous on adding the extra splits) but will get over it.

 

[kennyp2339]

kennyp2339 - thanks for the detail, this is helpful as well as the other posts. Understood on the secondary burn, I do achieve that when flue temp gets to ~425F, and it does dance nicely as you described. What flue temps would you expect to see on this model stove?
(nervous on adding the extra splits) but will get over it.

You have dvl black pipe and I'm assuming a probe thermometer going through the skin of the pipe? If that the case you should have flue temps in the 700 - 800's no problem.
The lower temps reflected as "ok" when you have single wall pipe and and a cheapo magnet thermometer on the outside, those are calibrated that the 400 deg ready in the "clean burn zone" really mean 700 deg f internally.

 

[moresnow]

Moresnow, yes it is a new GM 60 CAT stove. It is my first CAT stove as well. I have been reloading every few hours with two 4 inch splits, bringing flue temp up and then backing down the intact, all good. Are you saying to add more then just the two splits? When I do that, I get the lack of control over the increased flue temp. OR, will it settle down after a certain time? Sounds like my two split add is not the way to go? I just re-read the manual and it is not totally clear on reloading, but I believe I have been following the directions. As far as opening the door during burning, the manufacturer instructs to close the bypass, which I have done, then open and reactivate the cat after loaded. Your feedback seems to be right on. Any further comments are very much welcome.

Have no fear! You will get the stove ironed out in time. Confirm what method you are using to measure exhaust temp. Guessing it has to be a probe temp gauge inside the DVL instead of a magnetic surface gauge but I have to ask. 500 internal temp on a probe gauge is nothing to fear. If it goes twice that high. To hot. If you are measuring 500 on a magnetic gauge on DVL.... Look out! That's hot.

Starting a larger load will likely indicate temps you have not seen yet, and they will continue for some time. Eventually it will mellow out and float along nicely. Just have to find the sweet spot to set your air intake at.

On a reload procedure. Just to clarify. You typically open the bypass to let the exhaust go out without going through the Cat prior to opening the loading door. After the fresh load gets going well/hot you close the bypass to force the exhaust through the Cat.

I am going to invite a GM40 user here for additional operation guidance from his perspective. @Nigel459

 

[kennyp2339]

@moresnow I think @begreen has taught us well over the years, he's prob spitting his coffee at the computer monitor in sheer happiness.

 

[cabinwarmer]

You guys are giving me confidence! Yes to the probe questions, DVL with AT200 probe. I am coming from a 1.0 cu ft 20 year old Waterford, not used to these temps or cat or fire box size (I guess). I have the AH1 alarm set for 650 on the AT200 - just goes to show you my inaccurate mind set I suppose and will need to change that. I think the last thing I need to help me would be the draft measurement as suggested. Looks like the manual says anything in excess of 0.1 WC is an issue. You guys are the best!!

 

[begreen]

LOL. Truth be told, we are all learning all the time. Now in 2020, we have a new crop of stoves and it's time to learn all over. If I were younger and wealthier I'd probably consider trying a GM80 and a few other stoves.

@cabinwarmer I can appreciate your caution. It's like learning to drive and now getting ready for the first foray on an expressway. Work your way up to larger loads during the daytime when you can be around the stove all day. Start with 4 or 6 good sized splits on a reload. Watch the stove and note temps and behavior and know that it will settle down with the air closed after time. There will be an initial bloom of wood gases that will drive up temp in the cat and possibly the flue. You will have to tell us what you see.

To get a fire going on less coals, you can criss-cross some kindling on the coals when they are meager. I did that this morning and the fire started back up in about 5 minutes. If the wood is fully seasoned it will ignite. Do your best and let the stove teach you too. FWIW, my guess is that the active zone in the cat thermometer has a range more like 500 to 1500º. 1200º is not an unusual temp for a catalyst early in the burn. My Auber high temp alarm is set to 900º and yes, it goes off if I get distracted and forget to set a timer for closing down the air.

 

[moresnow]

You guys are giving me confidence! Yes to the probe questions, DVL with AT200 probe. I am coming from a 1.0 cu ft 20 year old Waterford, not used to these temps or cat or fire box size (I guess). I have the AH1 alarm set for 650 on the AT200 - just goes to show you my inaccurate mind set I suppose and will need to change that. I think the last thing I need to help me would be the draft measurement as suggested. Looks like the manual says anything in excess of 0.1 WC is an issue. You guys are the best!!

Oh my. A heck of a leap in technology! From a Waterford to a Auber and Manometer!

Unless you are into gadgets I wouldn't sweat the manometer gauge just yet. None of the 7 stove's I am around have one. Or ever have. On the other hand.... It is a great tool if needed. Good luck!

 

[Highbeam]

This stove is a hybrid so the secondary air system dumps in copious amounts of combustion air unrelated to the intake control setting. The higher flue temperatures when you load fuel are to be expected since the stove is designed to consume that bloom of fuel instead of puking it out the chimney as emissions. This thing is supposed to run hot, especially at the early stages. And you’re not supposed to be able to stop it because that would create high emissions.

The catalyst is there just to burn up whatever the primary and secondary combustion systems can’t catch. It’s working if it’s way up into the active range on the dial.

I think the biggest issue is you becoming comfortable with normal flue temperatures which are between 400 and 900. Your pipe is rated for 1000 degrees continuously and short durations at 1200.

I had a hearthstone noncat and even with the intake fully closed that thing would run at 800 degree flue temperatures.

My noncat nc30 in front of me now is idling at 400 stove top and 603 degree flue temperature. It’s just coals!

Trying to run your stove at super low flue temperatures is holding you back.

 

[cabinwarmer]

Oh boy......alot to digest. Anyone want to come over for an afternoon when I lite it up!??? OK......learning as we go.

 

[Highbeam]

At some point, like I did with the hearthstone heritage, you just load her up full and do as you’re supposed to. When it gets hot just shut the intake fully closed and sit down with a beverage and watch it. Watch the flue temps climb, level off, and eventually come back down. You need to do this to gain confidence that everything will be okay. You’re totally okay if flue temps sit at 1000 for 24 hours. You’re even fine at 1250 for a couple of hours.

Go outside, look at the emissions. Nice and clean. You might need to open a window if it gets hot inside.

The stove will earn your trust.

 

[cabinwarmer]

Highbeam, so far I have gotten as far in your scenario as "watch the flue temps climb", THEN I grabbed the beverage after I plugged up the intake, mostly because I need one.

 

[Highbeam]

Highbeam, so far I have gotten as far in your scenario as "watch the flue temps climb", THEN I grabbed the beverage after I plugged up the intake, mostly because I need one.

Had flue temps risen past 1000?

Beverages are always good.

 

[cabinwarmer]

No, I have not ventured into utilizing the advise I got today on here. All of which I am grateful and appreciate. I have not gotten above 575F yet. Nor have I packed the firebox as of yet as described above. It got around 575F when I loaded up for one of my early top down start ups. That was the first time I got concerned.

 

[Highbeam]

I’m cruising along at 720 now. Right in the middle of “normal”.

Part of the problem is people posting flue temps as measured on the surface. It’s way hotter inside as measured with a proper probe meter.

 

[cabinwarmer]

I’m cruising along at 720View attachment 268595 now. Right in the middle of “normal”.

Part of the problem is people posting flue temps as measured on the surface. It’s way hotter inside as measured with a proper probe meter.

Here I am "whimpy yet comfortable". Time to put on my big boy pants soon! I think part of why I am not going big with this stove is even at these temps, the room is at 72F. This thing really puts out after the stones get hot.

 

[Highbeam]

That’s “barely legal”!

 

[cabinwarmer]

That’s “barely legal”!

Yea, I knew that post would get some comments. That is even low for me, but was where the stove was at the time. I get it now......stay tuned. AND, thanks again to everyone for the guidance and encouragement.

 

[kennyp2339]

Only advice is to check your chimney often if you want to stay at lower temps, more of a chance of build up occurring, cap will get gummed up first.