Heatermeter on a Primo


 
J

JeremyDS

New member
I have two reasons for posting this thread. First, I want to give a big thanks to Bryan and Ralph. Bryan, this is a heck of a device you've designed and it is awesome that you are putting it out there for us to enjoy. Ralph, the RD3 is a really clever gizmo and I really appreciate your patience in helping me figure it out.

The other reason for this thread is to give a starting point for others that might want to pair the HM with a Primo Oval (I have the XL model). I did a lot of searching to see what settings work with the Primo and wasn't able to find much of anything. Maybe some other Primo owners can chime in with what works for them.

My initial HM setup was a basic one using a mounting plate for a Stoker WiFi kit. From their pictures it looked like their mount had a nice rectangular duct that I could mate to the HM blower. That ended up being a complete waste of money because the mount ended up being just a flat plate of metal with a rectangular hole. So I made this to hold the blower
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I did two cooks with the blower-only setup; a brisket and a pair of pork butts. There were some cool moments (lighting the fire as I was running out the door and coming back 3 hours later to find the grill right at 225-230 was pretty awesome), but I wasn't really happy with the blower control. It was really hard to get the top damper closed down enough that the blower actually had to do anything and there was too fine of a line separating "control" and "killing the fire". As a result the temp was constantly bouncing between my set point and +5-10 degrees. Also, my fuel consumption went up (still small, but noticeable). And it may have just been me, but I thought the butts came out a little drier than usual.

At this point, if I had dropped $400+ on a commercial temperature controller I would have been pretty peeved, but all those problems had already been addressed by the good people here. So, I contacted Ralph he sent me one of his RD3's (which I thought was a pretty cool device even before I realized it would allow me to leave my HMpi indoors during cooks). My hope was that the RD3 would do all the temperature control with the damper only so that I'd be able to regain the advantages of the kamado (fuel efficiency, humidity retention, temperature stability). My question was: just how high of a temperature could I cook at without the blower kicking in. Realistically, the highest temp I'd want to run without a blower would be 325-350 for a poultry cook. I planned to do a couple of chickens last weekend, but we ended up eating out or with friends every night. But, I was planning to bring my baked beans to our friends house, so I took the beans as an excuse to test out the Primo/RD3 combo. It did quite nicely
BakedBeans8-15arrow.png

The red arrow is where I tried to close the top damper down about halfway (with the daisy wheel still fully open). That clearly didn't work, so I opened the top all the way up and it settled onto the set point of 325 with the RD3 open about 60-70%. Based on that, I'm guessing the highest I can go with passive airflow is maybe 350 or a cool weather cook (i.e. Thanksgiving) at 325.
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Today I finally got a chance to try out the RD3 on a slow and low. Here is a 6 hour cook on a couple racks of spare ribs.
Ribs9-15arrows.png

There is a lot going on in that graph. After an initial (minor) overshoot, the HM slowly locked on to the set point of 225 (blower at 50% on startup, and 10% max only during cook). I started off with the top damper fully closed but the daisy wheel fully open. At the red arrow I realized that the RD3 was having to open up to 90% or so to maintain temperatures, so I cracked the top damper open by about half an inch (leaving the daisy wheel open). That seemed to work great for about an hour but then, for no apparent reason, the temperature started oscillating pretty dramatically. I started messing with the PID settings at the first green arrow, and at the second green arrow I settled on the BGE setting in the Wiki (P 2.5, I 0.0035, D 6). At that point I left for the afternoon, but when I got back I found that the oscillation amplitude was pretty much unchanged, but the period had gotten much longer. So I've still got some work to go, but at least the damper is spending less time at 100% and 0% so I'd call that an improvement. I'll update this thread as I get a chance to do more testing.

Jeremy
 
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When I use my RD3 for damper only control (blower on at Max Only) I start the grill with the top vent just cracked, the way you need to run it if you are doing a cook with the blower only..... When the pit approaches the setpoint and the HM starts to back off 100% I open up the top vent a nice bit, now it's time to put the food on. I watch the RD3, if it is running high like your graph shows I will open the top more until the RD3 starts running around 30% or so open. At this point the RD3 has plenty of range to control things.

So first off, I think you need your top vent open more. With the blower off you are using convection air flow, so the top vent has a lot more influence on how things go than it does when you use the blower. You are moving a step back toward manually controlling the pit, except the bottom vent is now automated... So, get your top vent into proper range and the RD3 should be able to handle the rest for you.

As for the oscillations, having a proper top vent setting can cure that, often times a little tweak to the top vents will smooth that right out. For a long cook you need to make sure your fire can still breath after it's been burning for a while. Depending on the grill and how you setup your coals ash can build up and choke off air flow, this can cause oscillation too. I dont have this problem on my Fauxmado, but my Uncle has a Primo and I found that I needed to go in through the vent and poke some ash out of the holes in the bottom of the ceramic burn pan mid way through a long cook to keep the air flowing like it did when the pit was freshly lit. When you lay out your coals grab them in handfulls and place them in the pit, don't pour from the bag, when you poor a lot of small chips and powder come out with the lump coal, this small stuff can choke out air flow to the coals quite a bit. You need to pay close attention to how you lay out the coals for a long cook if you want to go the whole cook without messing with them, otherwise you might need to poke around at your fire a bit mid cook....

PS You should be able to achieve a top end temp much higher than you report in damper only mode with the top vent open wider. I did a test a few weeks back and I had no problem holding 400F with the RD3 running about 30% open, the top vent was nowhere near wide open, so I know I could hold a lot higher temp than that without the blower running.
RD3_HH_OMO.jpg
 
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Thanks Ralph. I recall seeing you write somewhere that 30% was optimal for servo control. That is what prompted me to open the top at the beginning. If I had been planning to stick around for the rest of the afternoon, I probably would have opened it a bit further to get from 50% down to 30% but I wanted to change the variables one at a time. I'll keep playing around with it. I think I'm very close. Turning down the "I" setting was important. I might also need to turn up the "D" setting, once that ceramic starts changing temp it is going to keep moving. I think the HM needs to be more patient.

I definitely use handfuls of lump and don't dump. For an overnight cook I'll even go through the effort to make sure that only big pieces are on the bottom layer. But this was just a 6 hour rib cook and I've never had ash be a problem for something that short.

The 325 cook was with the top damper all the way open. Now that I have the image links fixed you can see that in the top post.
 
I find your top end temp for damper only mode to be oddly low tbhwy, but every grill is different I guess. When you run your grill without the HM, if you leave the top vent wide open and the bottom vent open about as wide as the RD3 output what temp can you achieve? The RD3 without the blower running should be able to achieve just about that same temp....

With a servo damper on the input the HM is a completely different beast, if you've used the HM with the blower only it takes a minute to get used to it... Most people need to clamp down really tight on the top vent with the blower only scenario, opening it up a tiny bit too wide will let your grill float away with overshoot. So you tend to get a bit paranoid about the top vent setting. With the servo damper in place, if your grill plate seals well to your vent and the rest of your grill is sealed up well you can pretty much bring the flow through the grill to a halt when the servo damper closes, so you can leave the top vent open much wider. In fact, it is essential that the top vent is open wider because you are depending on passive convection flow to stoke the pit....

If you are doing a higher than low and slow cook make sure you build/light the fire appropriately... You need a bigger fire to achieve higher temps, so light more coals and let the HM Blower stoke the pit up to temp (don't stop at low and slow then ramp up, with convection flow this can take a while. If you change from low and slow to higher temp setpoint power cycle the HM to reset the blower to run at Startup Max to stoke the fire up to where it needs to be fast). Keep in mind, with damper only it is the heat from the fire rising up that causes air to be drawn in through the bottom vent. A small fire will cause less flow and thus have less ability to draw air through the grill and stoke the pit. So it is important that you build the fire up the proper level when going the passive flow route.

One of the best things about the HM is it is so damn versatile.... So, if you do find convection flow is not getting you where you need to be then you can remove the "On at Max Only" for the blower, and set the blower MAX to something on the low side and let the blower assist the convection flow a little bit.

So, I suggest you get a few cooks under your belt with the RD3 (ATTENDED cooks, so you can watch what goes on and get a feel for how things are working), first experiment with the top vent settings to see if you can get where you need be, which I think you should.... If that isn't working out remove the Max Only setting for the blower and let it run a bit, experiment with the MAX setting for the blower to get to where you need to be...

PS One more thing... Make sure your RD3 is functioning properly.... If the servo fits tight and needs to be forced into the RD body it will bind and may not move properly. Widen the mounting hole to fit snug but not tight if that is the case. Also, the servo's vary a bit in size, shaft length etc... Sometimes if you tighten the screw down to much the RD will bind... Backing off the servo screw just a little bit will allow the RD to move more freely in this scenario... Just make sure the RD3 is moving the full range of motion and not getting hung up along the way... Finally, some servo's will let the shaft pull out of the servo body a bit. This will allow the damper disc to move away from the RD3 body and make the valve barely effective. If you have this issue (small gap between the damper disc and RD3 body) use the appropriate sized shim under the servo body to eliminate that gap.
 
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If you are doing a higher than low and slow cook make sure you build/light the fire appropriately... You need a bigger fire to achieve higher temps, so light more coals and let the HM Blower stoke the pit up to temp (don't stop at low and slow then ramp up, with convection flow this can take a while. If you change from low and slow to higher temp setpoint power cycle the HM to reset the blower to run at Startup Max to stoke the fire up to where it needs to be fast). Keep in mind, with damper only it is the heat from the fire rising up that causes air to be drawn in through the bottom vent. A small fire will cause less flow and thus have less ability to draw air through the grill and stoke the pit. So it is important that you build the fire up the proper level when going the passive flow route.
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I think you nailed my problem. My usual method of starting a fire is to stick a butane torch (the kind used to caramelize creme brulee) directly into the coals for 30-60 seconds. That is perfect for a slow and low, but you are exactly right that the fire will be too localized to create draft for higher temps. The next time I need roasting temps I'll use the charcoal chimney to get things started.

I think I found a nice balance between damper tightness and ease of motion. I'll check again, but it is moving freely and I don't see anything resembling a gap.

I'm definitely not worried about these issues. Between the damper and the controller, I have all the functionality I need. Right now my only problem is tuning the HM to my system (either damper settings or PID settings). I'll get that figured out after a few attended cooks...only problem is that the family is already getting tired of ribs!
 
I'm on a primo as well using a damper only control that I built to use the stock primo damper. I am not sure I have ideal PID settings yet but you can definitely do very well on these grills using only vent control. I agree with the others here you can leave the top vent open a lot more than you expect. In fact you may need to open it more than I do with an RD3, the air intake on an rd3 is a lot smaller than a wide open stock primo vent.

I'm still thinking of ordering one or using some kind of fan approach to get to cooking temp faster but vent control is all I've needed and I can easily hit 500+ even with the fire box divider in using the heater meter in vent control only mode.
 
OK, this is a LOT better:

PulledPork9-15.jpg


This is with the top damper open about 1.5 inches and the PID settings at (P 2.5, I 0.0035, D 10). These settings gave the HM close to the patience I would have in making adjustments. Things were really solid until right at the very end. Unfortunately, those fluctuations at the end ruined a good opportunity to test the ramp mode (I had ramp set to kick in at 190).

Ralph, I know you said I should do my next experiment with a monitored cook, and this was...sort of. I monitored it very closely from work. My colleagues were very impressed. :cool:
 
I have a Primo LG300 bbq and a heatermeter that is causing me some grief. When I plug the damper / fan the damper goes fully closed just sitting on the counter so you know what it is doing to my charcoal. I do not know how to attach pictures so if someone could help me out I will send a picture of my settings and fan/damper.

Thanks
 
So the damper only moves to fully closed and never does anything else? Was it working properly at one point?

You can upload your images to https://imgur.com/

After you upload, hover over the image and you'll see a \/ dropdown. Click on "get share links" and then copy the "BBCode (Forums)" link and paste the link ie:

[img.]http://i.imgur.com/IBd4ofw.jpg[/img]
 
I believe that it was working properly but I am fairly new to using this device so I am not 100 % sure. The imgur site says that it is overloaded so I can't down load. Some of the issues I have had is after I start the charcoal it will die out after about 15 minutes and I am guessing that it is because it is not getting air. It was working not to badly the few times I had used the unit but I was having problems with the WIFI adapter and I thought it was the Heatermeter but it was my WIFI router in the house. My son tried figuring it our for me so I think that he may have changed some settings so I am starting from the beginning again. When the fan is running I am not feeling any air coming from the unit and if I rotate the damper by hand I can feel the air so I think that there is a problem here. I will try and post pictures when the site lets me

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I have a Primo Oval jr and have got the HM dialed in nicely for a temp range from 180 up 400. My setting are as follows
P 3.5
I.0035
D 6
Fan/damper setting as follows
on 0%
min 0%
max 10%
startup 65%

I also run my thermocouple into the hole in the damper where the damper used to be held in place with a 10-24 screw. My unit is 2009 made and all I did was seal the top with adhesive gasket and then pocked hole in it and ran my Thermoworks thermos couple into the dome. I then gently formed the tip to be in the center of the dome and about the same level as the thermometer tip position. I am using a Adapt a Damper and this works well. I have my damper cracked open about a 1/8" at 225 degrees and maybe a 1/4" at 400 degrees. Once you get the settings set, just fine tuning the damper is all it takes to stabilize and tighten up the devices response. Don`t get on the chansing the PID dragon. Once you find settings that give you good response and stabile control, you got it. damper fine tuning does the rest. Also I have the older style damper and I think maybe there could be some issues with that design.
 
excuse my last statement. I feel my damper with the flat plate my be easier to adjust the stability than the newer plates with holes and flat plate. Also make sure you have good gaskets and do not have any leaks. You should be able to control at 225 t0 250 with the damper just barely cracked
 
I can see from your config that you've got the default servo settings, 1000us - 2000us, which is probably part of the problem.

Put the heatermeter into manual mode and use the up / down button movement to see how much servo travel you have between 0% and 100%

That damper should rotate about 90 degrees from fully close to fully open. You'll need to adjust the servo pulse duration accordingly. You might also need to enable "invert output" on the servo if it's not rotating in the proper direction.
 
I played with the fan last night on the table and the damper seems to work. When I set the temperature below around 100 degrees the servo opened and moved but when I put it at 225 it closed up and the fan ran at the 50% so I think that there is something wrong with my fan / damper servo settings but I have not idea what they should be. Just now I seen your post to someone else and I changed the 1000u to 2000u to 1800 which gave it about 90' opening. I also changed the "invert output" and this seems to havve fixed the fan running 100% with the damper closed. Could you please look at my other settings mainly the fan and suggest what these should be at to start.

Thanks
 
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You need to run it in manual mode and go from 0% to 100%

If the servo is closing the damper more as you climb to 100%, then you need to enable "invert output"
 
You have fan at max 50% which might be fine. The real issue is that if the damper is closing as PID output and fan output are increasing, you won't get any air into the fire box.
 
Steve_M said:
If the servo is closing the damper more as you climb to 100%, then you need to enable "invert output"
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To be a little more clear, there are TWO invert output settings. One is on the fan output line, one is on the servo line. Always leave the Fan Invert Output off, because that makes the fan run at 0% output and turns off at 100% output. The invert output on the servo line is used if the servo operation is inverted (the damper is wide open at 0% output and closed at 100% output).

Also as Steve suggested, you should use manual mode to get it all set up because it is easier to understand because it takes the temperature controller out of the equation. Set the setpoint to "0%" (or use the device's menus to set to manual mode) to get 0%. Is the fan running full blast? Make sure that invert output is off. Is the damper wide open? Adjust the servo invert output. Is the damper not fully closed? Adjust the pulse duration range. Now set the setpoint to "100%" and adjust the other servo pulse endpoint to make sure the damper is fully open.
 
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