RT-1070 Smoke from hopper when shutting down

[C. Keeper]

Not familiar with where you have this. More pics? Where is the air going?

I removed the original fan and replaced it with a higher CFM muffin fan. Long term, it didn't work.

 

[okie]

I removed the original fan and replaced it with a higher CFM muffin fan. Long term, it didn't work.

 

[okie]

Thanks. I think there is plenty of "air" power in RT grills. In fact there are times when air pressure exceeds discharge capacity and that is when the exhaust takes the exit through the auger tube and around the lid. This is enhanced on the 1070 by the very large surface area of the hopper top and the poor efficiency of the top as a seal, allowing low resistance to the air pressure. Windy days will enhance this by venturi effect in the hopper as well. Of course, another way to reduce this back flow would be to increase the size or number of exhaust air vents. But that might contribute to rapid temp loss and higher pellet use. So for me it seemed logical to seal the hopper lid. Two effects: stop reverse flow, and by secondary intention, reduce available O2 in the auger. I'd rather that the excess pressure be released elsewhere.

Another way to explain it in simpler terms is that the new 3 rpm auger delivers twice as many pellets on "high" and the products of this combustion is producing more exhaust gas volume than was originally expected. So it goes anywhere that the that the flow is not impeded (pressure is lower).
Am I windy or what?

 

[okie]

While happy to prevent this problem by sealing the hopper lid (if valid), I still think that having two holes in the fire pot straight across from the auger tube may be helping to initiate the lighting of auger pellets. Have had no response from RT on this.

But if sealing the hopper lid corrects the problem, who cares where the holes in the fire pot are? Not me! Another test this morning. Will go to "full" (or whatever it is called). Let it burn there for a while and then shut down as in tests #1-#3. So far, so good.

 

[okie]

Test #4 this AM. Ambient temp 62* Set the temp for "Full". Took 11 minutes to get to 500* and then on up to 585* before I turned it back down to 500*. I never use Full, but have had it up to 700* once on a test run. Kept it at 500* for 25 minutes. Opened and closed several times to mimic a steak cook. Then turned it down to 250* and waited. No hopper smoke and when it reached 320* I went ahead and hit Off cause I had a hunch that there would be no smolder, or hopper smoke at the end. It was another perfect shutdown.
Two things are apparent:
1. Heat sealing the hopper has no adverse effect on performance.
2. Heat sealing the hopper may be the solution to the problem of either post turn off smolder or hopper smoke--or both!
Plan: Keep hopper lid sealed. Report smolder or hopper smoke if and when. Silence on this matter otherwise. Thanks for the attention.

 

[C. Keeper]

Test #4 this AM. Ambient temp 62* Set the temp for "Full". Took 11 minutes to get to 500* and then on up to 585* before I turned it back down to 500*. I never use Full, but have had it up to 700* once on a test run. Kept it at 500* for 25 minutes. Opened and closed several times to mimic a steak cook. Then turned it down to 250* and waited. No hopper smoke and when it reached 320* I went ahead and hit Off cause I had a hunch that there would be no smolder, or hopper smoke at the end. It was another perfect shutdown.
Two things are apparent:
1. Heat sealing the hopper has no adverse effect on performance.
2. Heat sealing the hopper may be the solution to the problem of either post turn off smolder or hopper smoke--or both!
Plan: Keep hopper lid sealed. Report smolder or hopper smoke if and when. Silence on this matter otherwise. Thanks for the attention.

Time will tell, please keep us updated.

 

[okie]

4 hr spareribs this afternoon at 275* 4 hrs. Normal shutdown. Ribs were great also.

 

[Grilltreats]

All good points. I have a question: If the hopper lid is sealed against draft, then there can be no progressive auger burn and smoke cannot enter the hopper since there is no air flow in that direction. Would most of us agree to that? On the 1070 the hopper lid just lays on the edges of the hopper and makes no real seal. I'm sure back draft can occur, especially on windy days. On my old 590, the lid was held firmly by a snug fastener so that very little space was left to leak, I did not have smoke ever come thru. Also the auger tube was much longer which probably helped insulate the hopper from blow back. So--- in my previous note today, I showed a nice seal around the hopper top where it lays on the hopper edges. I just happened to have the typical 1/8" Lava Lock from another time, so I used it. I just finished a 500* 30 minute burn and made efforts to open and close the lid to mimic a steak cook. Then turned the temp down to 250* and let it get down there and be stable for 10 minutes. Then hit the off button. Results: perfect shutdown with no smoke in hopper or any smoke after it turned off. I know this is a one timer, so I will repeat a couple of more times. Can't imagine any warnings from RT with this mod, as it does not impair proper exit of exhaust from main smoker area. Let me be the guinea pig on this, till we have more favorable shutdowns. I will keep track and report back and you can all decide if it is worth the trouble on the 1070 (or perhaps even the 700 if needed since they both have similar hoppers with short auger tubes).I would appreciate comments Pro or Con.

I put a seal on my 700 hopper lid very soon after getting it. I haven't had any shutdown or damp pellet issues in five years now except for one time when it was really windy out and the hopper was near empty. I put some foil over the air intake below the hopper which snuff out the hopper smoke. This only happened once, and I never leave the hopper that empty anymore.

 

[okie]

I put a seal on my 700 hopper lid very soon after getting it. I haven't had any shutdown or damp pellet issues in five years now except for one time when it was really windy out and the hopper was near empty. I put some foil over the air intake below the hopper which snuff out the hopper smoke. This only happened once, and I never leave the hopper that empty anymore.

Well, I did my 6th cook (burgers) and just set it for 485* since I get plenty heat on my GrillGrates to do burgers at any temp above 450*. After about 20 minutes at that temp they were done, so I left it at that temp for 10 minutes to burn off the drippings, then turned down to 250 setting, but decided at about 350 that maybe I did not have to let it cool down first. Wrong! Turned off at 350* and all went well until it finished the shutoff cycle. NO smoke in the hopper! But long smolder out of the exhaust vents. Took it apart while still hot and smoky (oven gloves required). Both the pot embers and smoke from the auger tube as well. With the pit off, I entered the test mode and ran the auger until no black or smoldering pellets were exiting the tube. There were about 1.5 inches of black pellets in auger. So once out of 6 hot cooks, I got auger pellet ignition, but no smoke in the hopper. Lesson: be patient and let it burn down to 250* and stay there for 10-15 minutes before the shutdown. My hopper seal was intact. So still an experiment in progress.

 

[C. Keeper]

Well, I did my 6th cook (burgers) and just set it for 485* since I get plenty heat on my GrillGrates to do burgers at any temp above 450*. After about 20 minutes at that temp they were done, so I left it at that temp for 10 minutes to burn off the drippings, then turned down to 250 setting, but decided at about 350 that maybe I did not have to let it cool down first. Wrong! Turned off at 350* and all went well until it finished the shutoff cycle. NO smoke in the hopper! But long smolder out of the exhaust vents. Took it apart while still hot and smoky (oven gloves required). Both the pot embers and smoke from the auger tube as well. With the pit off, I entered the test mode and ran the auger until no black or smoldering pellets were exiting the tube. There were about 1.5 inches of black pellets in auger. So once out of 6 hot cooks, I got auger pellet ignition, but no smoke in the hopper. Lesson: be patient and let it burn down to 250* and stay there for 10-15 minutes before the shutdown. My hopper seal was intact. So still an experiment in progress.

I wonder if getting rid of the 5 minute fan run timer would help?

 

[okie]

I wonder if getting rid of the 5 minute fan run timer would help?

Tested again today at 500+ and turned down to 220 and stabilized before turning off. Worked perfectly!

 

[okie]

Tested again today at 500+ and turned down to 220 and stabilized before turning off. Worked perfectly!

Cook #8 Steaks at 500* tonight. After removal of steaks activity, the temp went up to 560* (had the lid open for while when removing steaks). So we ate dinner and I waited till the "bonfire" was over, and temp back down to 500*. Then turned down to 220*. Then when it reached 220, started shutdown after 10 minutes. Flawless shutdown. I'm done on this thread. Thanks for all the comments and input.

 

[okie]

Long term follow up. The delayed shutdown process from hot cooks has been used several more times and works perfectly. The hopper lid seal has not shown wear and tear after many open and closings.

 

[okie]

Long term follow up. The delayed shutdown process from hot cooks has been used several more times and works perfectly. The hopper lid seal has not shown wear and tear after many open and closings.

Update: Did a 500* hot cook on Dec. 31. Forgot to wait for temp to stabilize before turning down to a low temp. Result: Had a typical post shut off auger burn for about 12 minutes. Let it go out and later found it burned about 2 inches into the auger tube.(after the pellet feed at the end of shutdown!).
Lesson: After opening and closing during hot cook, let it stabilize back down to set temp before turning down to shutdown temp. (usually around 225-250). AND maybe that will always work?

 

[C. Keeper]

Update: Did a 500* hot cook on Dec. 31. Forgot to wait for temp to stabilize before turning down to a low temp. Result: Had a typical post shut off auger burn for about 12 minutes. Let it go out and later found it burned about 2 inches into the auger tube.(after the pellet feed at the end of shutdown!).
Lesson: After opening and closing during hot cook, let it stabilize back down to set temp before turning down to shutdown temp. (usually around 225-250). AND maybe that will always work?

My next mod is an auger bypass switch. This will allow me to feed pellets to avoid the burn back issue.

 

[okie]

My next mod is an auger bypass switch. This will allow me to feed pellets to avoid the burn back issue.

And if you end up with a too big pile of pellets in the pot you will get a bonfire then or when you light up again. I find it easy to clean out the pot and run auger in test mode to purge tube and prime the pot. Since I can avoid the burn back if I remember to shut down properly, and after all I had about 15-20 cooks without incident. As said before: "Time will tell."
Hmmn, auger bypass switch. Isn't going into test mode to turn auger on and off almost as easy?