RTD probe experiment...

[680bear]

How much better was the more expensive Savanah probe versus the Bitt Boss probe?

the results were virtually exactly the same so I have left the Savanah probe in...

 

[680bear]

I assume that the load of pan/briquets/steel plate does not interfere with the placement of the drip pan (the space between is limited)? Bit more of a chore when cleaning? Warm up time extended?

I like the results with the shortened RTD but wonder if you could have achieved the result with the temp diversity, by just moving the diffuser a bit off center to deflect the heat more to the weak side? We old Traeger owners did that with great success. As I recall, I had a 15*-20* difference on left and right sides of the grates and moving the diffuser about 1/2 inch did the trick.
However, it appears that you have resolved the problems very well to your desires. Congratulations.

PS. I have decided not to replace the RTD on the 380. I use it for hot/sear/medium temp short(chicken) cooks and use my 590 for the Low/Slow. The Offset changes I made earlier seem to have been satisfactory for the 380.

The diffuser plate in the 680 can't be moved over,,, it has cut outs that provide for the auger...

 

[680bear]

Here is the final outcome of the diverter mod,,, I may still box in the sides and attach the steel plate so it comes out as a unit,,, but it's easy enough to lift out without removing the ceramics as it is now,,, with this the temperatures across the grill surface are within 5° side to side,,, and I no longer have to adjust the temperature offset for the RTD... I call this experiment complete and finished...

 

[okie]

I forgot about the center auger feed on 680. In looking at your pics, I would be interested in doing one more simple experiment if for no other reason than accomplishing the same result with less stuff to move.
Take out the ceramics and keep the steel plate on. Move the steel plate away from the lower temp side toward the hotter side, enough to even the temps on both sides. Probably no more than 1/4 to 1/2 inch. Same as moving the heat deflector. Just a suggestion. Why would I do it?
1. simpler setup if it works. IF. I like simple.
2. shortens heat up time by whatever the ceramics take to get to set temp. And shorter cool down.
3. Easier cleanup.

 

[Roaniecowpony]

no worries,,, if we can all contribute and learn from each other it just makes things that much better for everyone,,, if what I am doing here with my 680 helps out someone even if they don't have the same grill,,, it's all worth it...

Early on when I got the RT700, I did some location testing across the grill. I got some pretty large deviations as well. I didn't pursue it further, as you did. I have noted that I need to rotate positions of racks of ribs to get them to all cook at the same rate as well.

My thoughts go to how hot the pellet burn pot has to run at. Looking at the flame color, I would guess it burns at up to 1200-1300F (max, when going wide open blower for long periods) and much lower when smoldering and low blower use. Evenly dispersing these high temperatures with just the two OEM diffusers as well as they do, still won't be perfect. Adding more diffusers as you did, is a step to fine tuning the Bull.

Good work on the diagnosis and solution.

 

[jasonvr]

Here is the final outcome of the diverter mod,,, I may still box in the sides and attach the steel plate so it comes out as a unit,,, but it's easy enough to lift out without removing the ceramics as it is now,,, with this the temperatures across the grill surface are within 5° side to side,,, and I no longer have to adjust the temperature offset for the RTD... I call this experiment complete and finished...

So it looks like you've settled on the ceramic briquettes directly on top of diffuser now with the steel plate resting on the lips of the diffuser right above the briquettes, correct?

I recently did some testing with my Thermoworks air probe as compared to the RTD in my Bull and found about a 20 degree difference between the two (Bull reading 20 degrees higher than actual on the Thermoworks). I've been meaning to do some more testing when I have a chance, but like the looks of this setup. I have definitely noticed the right side being hotter than the left, so this would help as well. I still need to look at my offset on the controller as well as I may have changed it which might account for my offset.

 

[mshaefer]

I don't think there is a delay built into the controller because after I swapped out the RTD the temp during preheat would climb degree to degree with my thermoworks probe... the most accurate RTD probes are made out of platinum,,, I don't think the RecTec probes are,,, I haven't cut one open to have a look,,, but they definitely don't act like the platinum probes I have dealt with in the past...

Pretty sure they're labeled as Pt1000 probes. Not sure what other metal is used for a 1000 ohm RTD.

 

[mshaefer]

Here's one I wonder about: 4 pt1000 RTDs connected in series-parallel (i.e. two pairs of parallel RTDs, with those pairs connected in series). Wouldn't that return an average of the four (i.e. each paralleled pair would return half its impedance, and then those two halves would be added together for a whole), and make it so you can read the overall average temperature taken from four corners of the barrel?

 

[C. Keeper]

Here's one I wonder about: 4 pt1000 RTDs connected in series-parallel (i.e. two pairs of parallel RTDs, with those pairs connected in series). Wouldn't that return an average of the four (i.e. each paralleled pair would return half its impedance, and then those two halves would be added together for a whole), and make it so you can read the overall average temperature taken from four corners of the barrel?

Sounds like you're right in theory.

 

[fullhouse32]

My neighbor and I were taking about that the other day. Why is it only on one side. And 6” off the grill.
He showed me so pictures of companies the have shorter RTDs or have turned them sideways to be closer to the grates.
BUT all that side, I’m am sure the engineers at RT have thought the same things.

 

[C. Keeper]

My neighbor and I were taking about that the other day. Why is it only on one side. And 6” off the grill.
He showed me so pictures of companies the have shorter RTDs or have turned them sideways to be closer to the grates.
BUT all that side, I’m am sure the engineers at RT have thought the same things.

IMHO it's about the cost to manufacture the RT-B380.

For an entry level pellet smoker it's not too bad of a deal. Do you need 100% accurate controls on a pellet grill, no. When you compare a Weber kettle to the Bullseye, the Bullseye is a lot of bang for the buck.

I was one who played with the temperature settings and concerned about the RTD location till I checked my home oven. My oven isn't that tight of control either and in the grand scheme it doesn't seem to make a difference.

 

[mshaefer]

Just ordered 4 pt1000 rtds off aliexpress, will let y'all know what comes of the test. The idea is to wire up 2 pairs each in parallel, and then wires those parallel pairs in series to each other. At 0C, in theory, 2 1KΩ RTDs in parallel would return 500Ω resistance. Put two pair of those pairs in series, and you end with a resistance of 1KΩ. Now vary the temp each of the 4 RTDs is exposed to and you will vary the resistance of each one (R1, R2, R3, and R4) Hooked up in parallel-series like this (again, in theory), the total resistance should come out as (1/((1/R1)+(1/R2))) + (1/((1/R3)+(1/R4))), which is basically the average resistance of all 4. Just fiddling around with pt1000 resistance tables and throwing in four random temps +/- 5-10 degrees off from each other, it theoretically returns an average resistance across the whole circuit. It's this average that the controller should see and *should* then display an average temp of the barrel based on wherever the 4 measurements are taken. We'll see.

 

[C. Keeper]

Just ordered 4 pt1000 rtds off aliexpress, will let y'all know what comes of the test. The idea is to wire up 2 pairs each in parallel, and then wires those parallel pairs in series to each other. At 0C, in theory, 2 1KΩ RTDs in parallel would return 500Ω resistance. Put two pair of those pairs in series, and you end with a resistance of 1KΩ. Now vary the temp each of the 4 RTDs is exposed to and you will vary the resistance of each one (R1, R2, R3, and R4) Hooked up in parallel-series like this (again, in theory), the total resistance should come out as (1/((1/R1)+(1/R2))) + (1/((1/R3)+(1/R4))), which is basically the average resistance of all 4. Just fiddling around with pt1000 resistance tables and throwing in four random temps +/- 5-10 degrees off from each other, it theoretically returns an average resistance across the whole circuit. It's this average that the controller should see and *should* then display an average temp of the barrel based on wherever the 4 measurements are taken. We'll see.

My only concern would be that you could have sensor #1 and #2 reading really high and and sensor #3 and #4 reading really low but the average being okay. Hope that makes sense??

 

[mshaefer]

My only concern would be that you could have sensor #1 and #2 reading really high and and sensor #3 and #4 reading really low but the average being okay. Hope that makes sense??

Absolutely does. You wonder if that would be the condition inside the barrel? I'm pretty new to rec teq, so where would you think the four best places would be? My thoughts were the four corners, but i guess I could just sort of sample around the space and see.

 

[C. Keeper]

Absolutely does. You wonder if that would be the condition inside the barrel? I'm pretty new to rec teq, so where would you think the four best places would be? My thoughts were the four corners, but i guess I could just sort of sample around the space and see.

To be honest I don't think it will make a difference.

I have had several very reasonable conversations with RT and my take away was don't mess with the default settings and does the temperature really matter if it is off.

When I was doing critical environments sensors they were tightly controlled (and expensive) with everything documented. I have just come to accept the Bull for what it is, a pretty solid grill.

Please, don't let me deter you with your test. I just don't know how this info will help without spending more money to correct the newly found deficiencies.

If it were me I'd learn which area of the grill is "hot" and rotate the food to get an average cook temp and most importantly enjoy the grill.

Perhaps I'm just getting old and lazy.

 

[charlesrshell]

I know most of you don't agree with me but I still think if there was an old fashion thermometer mounted in the hood would be able to give you another tool to know what is going on. It would at least give you a quick indication if you have a grease fire going on.

 

[C. Keeper]

I know most of you don't agree with me but I still think if there was an old fashion thermometer mounted in the hood would be able to give you another tool to know what is going on. It would at least give you a quick indication if you have a grease fire going on.

Absolutely agree, I have been looking for a thermometer for the Bullseye lid. I haven't found anything I like with a short probe length.

 

[fullhouse32]

Very true, if there were multiple RTDs in the barrel you would get the same indication of a grease fire.
My smoke tube flamed up and the RecTeq set a alert that it was above set temperature.