Help. Low Pit Temp with MicroDamper & HeaterMeter

[RalphTrimble]

I dont think you're gonna get enough natural convection flow to control a UDS well... The easiest way to get a stable temp is to run both the damper and blower the full range (damper fully open at 100% and blower on above 0%), from there just tweak the MAX fan setting to suit your pit, that is the easiest path to stability. If you had an insulated kamado you'd be able to go full convection, they're smaller and they hold heat so well, but a UDS is quite large and thin walled so it's gonna bleed a lot of heat so you're gonna need the fan to stoke it....

 

[John Bostwick]

Nope a UDS, is very stable without any blower. You just need to know where it has it's stability at. Mine will stay perfectly at 230°f all night long, without a blower when I did not have a heatermeter. As long as you set your ball valve correctly it will be very stable. That's why I can smoke for 40+ hours, without adding any lump. In fact, I left it going for a 3 day period, although I turned it down too a point it was jist smoldering but, as soon as I opened the ball valve and one my extra inlets I had on my older UDS, I was back to smoking at 230 within a hour.

I will say my current UDS would have issues holding a high temp, 250+ if I just had the ball valve open all the way, as I don't have any other inlets and only rely on the heatermeter.

 

[RalphTrimble]

Do you run your UDS with the damper only, or do you use the blower?

 

[Dave Pasma]

Do you run your UDS with the damper only, or do you use the blower?

In case your question was directed at me, I have run it both ways. When I built my Heatermeter, and bought my RD, I wanted to control the convective airflow with only the damper connected to my 1" inlet ball valve.

My first cook went OK at first, but gradually, the temp began dropping even with the damper open 100%. I had to use the blower in the "On at max" - to keep the temp at the setpoint - usually around 230 degF.

Next, I tried attaching the RD to my other inlet. My hope was that I could adjust the ball valve on one inlet, and then let the damper control the UDS through the other (non-ball valve) inlet. That didn't work either. If the ball valve was open too much, the temps climbed. Then it would drop after I adjusted it.

The most recent cook, I decided to try using the blower in conjunction with the damper. That seemed to go fine. I smoked a brisket overnight. The temps stayed pretty steady, and I actually got some sleep. The main reason I called this one a failure was that I ran out of charcoal after only about 7 or 8 hours at 230 degF. In all previous cooks on my UDS, I never consumed fuel that quickly.

 

[Dave Pasma]

How much does a diffuser affect temperature control?

I am beginning to think that my setup INSIDE my UDS could be the reason why I have trouble controlling the temperature - even with a Heatermeter and RD. I guess I should put my concerns aside, and try running it with little or no diffuser/diverter above the charcoal grate?

I use a Weber charcoal grate with expanded metal wrapped around it, and 2-3" bolts as feet. Every time I cook (so far), I put a strip of 12" foil on the first grate above the basket. On that, I put 2 bricks, and on top of that, I put a rectangular foil pan 1/2 filled with hot water. The meat goes above the water pan, on one or both of my cooking grates. I put the temperature probe near the meat (but not touching) - to keep it out of the hot air flow near the side of the UDS.

Could this be doing one of two things?

1) Could it be impeding good convective airflow - making the air and smoke divert around the foil and water pan?

2) Could I be overdriving the charcoal because the air has to be high enough temperature to satisfy the temp probe that is on the grate, next to the meat?

 

[Dave Pasma]

Pics of UDS Internal Setup - 1 of 2

In this photo you can see the foil and foil water pan above the charcoal basket.

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[Dave Pasma]

Pics of UDS Internal Setup - 2 of 2

In this photo you can see the upper meat rack and the temp probe position. If the meat takes up more space, I usually lay it down on the grate, near the meat.

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[John Bostwick]

Dave, I see a flaw in your design of your Uds, your cooking grates are way to low. The first grate should be atleast 24 inches from the top of the charcoal basket. Any closer and you should use a difusser, as you said you were using. Without a difusser, your setup would be no difference then smoking on a Weber grill.

 

[John Bostwick]

Here is an old pic of my upper grill height. I do have one grill below that, which about 6 inches down, I believe.

 

[SteveCK]

Nope a UDS, is very stable without any blower. You just need to know where it has it's stability at. Mine will stay perfectly at 230°f all night long, without a blower when I did not have a heatermeter.

^^^^This. UDS can be super stable. The problem is not every UDS works the same, some prefer lump over briquettes, some prefer to run at 220 and others at 275. Two identically built UDS will have a different sweet spots - I know this because I've built and run half a dozen of them. It's best to know what your pit likes to run at before you try to force it to do things it doesn't want to. It's kind of like my pet Bulldog (stubborn).

 

[Dave Pasma]

Dave, I see a flaw in your design of your Uds, your cooking grates are way to low. The first grate should be atleast 24 inches from the top of the charcoal basket. Any closer and you should use a difusser, as you said you were using. Without a difusser, your setup would be no difference then smoking on a Weber grill.

I see what you are saying. But when I used to smoke on my Weber, I used the indirect method - coals on one side, meat on the other, or coals on both sides with a pan in the middle, and the meat above the pan. I never smoked meat using coals directly below the meat.

 

[Dave Pasma]

^^^^This. UDS can be super stable. The problem is not every UDS works the same, some prefer lump over briquettes, some prefer to run at 220 and others at 275. Two identically built UDS will have a different sweet spots - I know this because I've built and run half a dozen of them. It's best to know what your pit likes to run at before you try to force it to do things it doesn't want to. It's kind of like my pet Bulldog (stubborn).

Do you run your UDS with a diffuser?

 

[SteveCK]

I have two cooking grates. The top one is 2" below the top lip of the drum (I use a weber lid to fit food on this grate), and the second grate is 6-8 inches below that (I don't remember exactly). When I cook I throw a disposable hotel pan on the second cooking grate to catch drippings.

 

[RalphTrimble]

I just read through your recent posts and have a few comments. First, I dont think you mentioned your top vent settings? If you are going with convection air flow the top vent settings have a lot to do with the temperature range you can achieve. I would open up the top vent more and see if you can hit your target with just the damper, if you still fall short shoot me an email and I will print you an RD25, which has a much larger valve opening. The RD25 will use all the same parts from your RD3, the blower would be optional if you went strictly convection, but the RD25 blower can often be found used for less than $5.
I hear you on how using the blower makes you burn more coals, but forced air does have the ability to achieve higher temps and recover them faster, and stoke up a waning fire.... If you do end up needing forced air I think you should give an air-burner a try. The little air jets directly under the fire make very effective use of the air flow so you can keep it to a minimum. They stoke the fire real good, with the air blowing directly on the fire rather than pumping a bunch of cold air in the pit that just flows around the fire.
But again, the easiest way to have a HM control a pit and get a nice flat line temp is to use the blower and damper the full range of output. It may burn more coals but it is the "easy button" method....

 

[John Bostwick]

^^^^This. UDS can be super stable. The problem is not every UDS works the same, some prefer lump over briquettes, some prefer to run at 220 and others at 275. Two identically built UDS will have a different sweet spots - I know this because I've built and run half a dozen of them. It's best to know what your pit likes to run at before you try to force it to do things it doesn't want to. It's kind of like my pet Bulldog (stubborn).

I thought I posted a comment earlier, but don't see it.

Anyways, that's why I told him to find that sweet spot, as all UDS have a temp it likes.

But, where he is smoking, regardless of temps, he is going to have lots of problems keeping a stable temp. Let's say he wanted to smoke at 230 on his lower grate, the temps would be around 170 give or take some degrees at where the grate should be at. It's really hard to keep an UDS at temps lower then 170°(On mine atleast) and be stable. Plus his thermocouple will react very differently when it's not insulated with distance between it and the coals.