My First Major Burnback

[Pacman]

So all of you sleuths see if you can figure out what happened.

So on my picanha cook, everything seemed to be going to plan until all of a sudden I decided to effectively start a pretty respectable backburn hopper fire. I was able to shut things down, relocate the meat to finish in the oven, and then purge the auger in test mode. I pulled the drip pan and heat deflector and didn't see anything particularly weird.

Here were my variables:

1. Relatively clean Recteq with only one pork rib cook on it since last full cleaning.
2. Bear Mountain Gourmet pellets (with a few long pellets observed).
3. Ambient temperature outside was 109 degrees.
4. Internal pit temperature before starting the Recteq was 110.
5. I thought I'd be "smart" and start with the lid open for the first time ever given the heat.
6. Startup was uneventful.
7. Pit temp was below what the Recteq ambient probe reported (around 175 degrees) even though the controller reported 200.
8. I was about to crank up the set temp to begin my sort of reverse sear and saw smoke billowing out of the hopper, but not in the pit or out of the smoke stack.

I suspect the external ambient air temperature caused things to go haywire or behave out of character. Nothing seems to be wrong with the grill. All of the test mode stuff checked out okay. I'll do a thorough cleaning and do some more tests in cooler temps, but this was a first for me.

 

[C. Keeper]

Oooops

 

[Thor8594]

Sorry to see this. This is how all of my summer cooks are here in Arizona, half of the time I think why even turn on the grill it seems hot enough already. Knock on wood, I don't see this in future cooks. Not sure what happened to your cook, just strange.

 

[Pacman]

Yeah, I think this was sort of a "perfect storm", but I figured I'd see if anyone had any insights. In the end, it was no big deal. I'll know more once I clean everything up including probably vacuuming out the hopper just to make sure I don't have any pockets of partially burned pellets lurking around.

 

[Nerdygrrl]

How long into the smoke were you?

All of the major brands seem to struggle in high heat but I really do believe what you experienced comes down to the design/engineering on the RT's. I know I am new here, but I am not new to smoking or pellet smokers. I've cooked on commercial smokers, offsets, etc. I have never seen so my instances of smoke explosions or back burns as I have here.

If you call RT they will tell you it's because of the lid seal, but we all know that is BS.

 

[Pacman]

I was about an hour into the cook at a set temp of 200. The whole thing was totally out of character for at least my 1250. I've had zero issues with probably over 100 cooks. Sealing both the lid and the hopper early on solved a number of issues with smoke leaks, burn backs, and moisture into the hopper. For me this was a fluke. I still figured it would be interesting fodder for the group here.

 

[Nerdygrrl]

I fired up mine the other day, in the 90's here. I can't even remember what I was smoking. It was set to low and the thing had 30 degree temp swings the entire time. I don't think these controllers are all that great.

My guess is it was just that a lot of back and forth with the controller trying to maintain a temp and feeding and cooling, etc.

Do you have a readout of your temps?

 

[Pacman]

Here's the story from my Thermoworks Signals. I just finished cleaning out the firebox, auger tube, and completely emptying the hopper. Ash level in the pit was about what I'd expect. Nothing unusual in the fire pot. All air holes are clear. The fan test ran perfectly.

My diagnosis now is a build up of residual pellet sawdust in the auger tube and maybe a pellet bridge at some point. I found a bunch of disintegrated pellets by the time I got down to the bottom of the hopper and purging the auger tube. I saw evidence of previously smoldering "dust" in the auger tube. I have not completely emptied the hopper and auger tube in a couple of years. I guess I'll add that to my annual housekeeping.

 

[Buckeye1]

I’ve had one burn back on my bullseye I think it was one of three things or a combination of the three:

Bad pellets real dry and crumbly so maybe burning easier

Fire pot had a lot of ash allowing flame to get to auger

Dirty exhaust vents damn near blocked, probably causing back pressure in grill

 

[BigDan]

I’m just about to seal the lid on my 1250 to
Prevent smoke loss. I still get a ton of smoke even with the loss but figured what the hell. Reading different folks opinions on the hopper being sealed I’m still on the fence. Is there any real concern sealing the hopper? Everyone has a different opinion.

 

[Threadcutter]

I’m just about to seal the lid on my 1250 to
Prevent smoke loss. I still get a ton of smoke even with the loss but figured what the hell. Reading different folks opinions on the hopper being sealed I’m still on the fence. Is there any real concern sealing the hopper? Everyone has a different opinion.

I have a 700/Bull. I sealed my lid and hopper lid. Biggest thing for me ? It gets rid of the "clangin' and bangin'" Other than that, no concerns here.

 

[Pacman]

I’m just about to seal the lid on my 1250 to
Prevent smoke loss. I still get a ton of smoke even with the loss but figured what the hell. Reading different folks opinions on the hopper being sealed I’m still on the fence. Is there any real concern sealing the hopper? Everyone has a different opinion.

Sealing the lid was a no brainer for me. Sealing the hopper lid was out of pure vanity after I liked the "soft close" of the main lid. After a VERY wet winter, my pellets stayed perfectly dry and I had zero issues until now. More and more I'm blaming the pellets (not the same ones that rode out the winter).

 

[Jim6820]

More and more I'm blaming the pellets (not the same ones that rode out the winter).

I think you are on the right track here. Are the ones you were. using at the time something new?

 

[Pacman]

Yes, they were the Bear Mountain ones that I bought when they were offering BOGO and free shipping quite a while back. They had been sitting in their original bags in a dry garage, but it's been since late January/early February. Usually I relocate pellets into 5 gallon buckets for ease of use, ease of storage, and a little extra protection from the elements/humidity.

I bought 80 lbs originally. I just re-discovered my last two bags. So in other words, I'm not bashing Bear Mountain, just the totality of circumstances.

 

[Jim6820]

Yes, they were the Bear Mountain ones that I bought when they were offering BOGO and free shipping quite a while back. They had been sitting in their original bags in a dry garage, but it's been since late January/early February. Usually I relocate pellets into 5 gallon buckets for ease of use, ease of storage, and a little extra protection from the elements/humidity.

I bought 80 lbs originally. I just re-discovered my last two bags. So in other words, I'm not bashing Bear Mountain, just the totality of circumstances.

I would think that if the bags are still sealed, there shouldn't be a problem. I've had several bags of RT Ultimates hanging around in sealed bags for nearly two years and they haven't seemed to be affected.

 

[Nerdygrrl]

I think it was the heat and the controller. Your temp swing was kind of what I experienced the other day. Except mine were more consistent so the controller was feeding and stopping to try to maintain the temp. It wasn't capable of doing so. I had swings from 170-210 all cook long when I was set at 180.


Yours looks like you had a flameout and then it caught back up causing the spike. My guess is your pot was full from the controller over feeding when it dropped down and it took a bit to catch and then burned back.

 

[Waterboy]

The theme here seems to be the grills are having a hard time maintaining consist low temps in hot ambient . Is it possible you need to adjust the minimum feed rate during the hotter summer months? It sounds like you are getting too many pellets in the fire pot and the controller doesn’t want to burn them because it’s trying to maintain a lower temperature. Once those pellets get piled up around the auger the fire just starts making its way back up the auger.

 

[Pacman]

Cleaned everything and started with all new pellets. Even left the lid closed on startup (which I debated about). After @Nerdygrrl started talking about Char Siu, I did a weekday fake version with a pork tenderloin. Looking and smelling good so far. I'm in the home stretch and my steamed bao buns are hopefully going to finish right about the same time.

We now return to our normal cooking channel.

 

[Jim6820]

steamed bao buns

I love pork tenderloins and then you hit me with “steamed bao buns!” That’s a killer combination! If the Ferrari wasn’t at the tune-up shop, I’d be headed your way, pedal to the metal!

 

[okie]

I’m just about to seal the lid on my 1250 to
Prevent smoke loss. I still get a ton of smoke even with the loss but figured what the hell. Reading different folks opinions on the hopper being sealed I’m still on the fence. Is there any real concern sealing the hopper? Everyone has a different opinion.

“Okie Physics”; Flow (smoke) goes from high pressure to low pressure!
If you seal hopper lid then no flow into auger or hopper. Thus no (or less risk) of fire in auger or hopper.
RT says do not seal the lids for a reason: ? Perhaps to allow for release of extra combustion gases? They never would tell me why, but it makes sense. I suspect they have tried to design exhaust venting to be adequate without being excessive so as not to lose heat. But there are times when exhaust gases exceed venting capability. So it will take the path of least resistance and that may be the auger tube and hopper. For those who seal the smoker lid but not the hopper lid: (you know the rest).
Bottom line:
1. Seal the hopper lid.
2. Don’t seal the smoker lid.
3. Accept the soot stains or clean around the lid as needed. No one judges Q on the basis of the appearance of the pit.
4. Yes—vacuum the bottom of the hopper and auger entrance several times a year depending on usage.