Help. Low Pit Temp with MicroDamper & HeaterMeter


 
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Bob O

New member
Hi, I am hoping someone can help me out. I can barely reach a 200 degree pit temperature after more than 3 hours on my 18” WSM with the fan running 100% and the MicroDamper wide open.. Lack of incoming combustion air seems to be the problem as opening the door will make the pit temperature shoot up.

I am running a newly built HeaterMeter and MicroDamper with 10cfm fan. My WSM has a full gasket set and I keep the lid vent open 100% and the bottom 3 vents closed all the way since I am assuming you want the MicroDamper to control combustion air 100%.

From the MicroDamper I had a 1” to ¾” reducer to ¾” copper pipe running into the the charcoal bowl to a ¾ inch copper pipe manifold with sixteen 3/16" holes drilled in it. I removed the manifold and ran the pipe straight into the charcoal bowl below the charcoal grate thinking the back pressure was too great for the fan and that only made a small increase in temperature.

Last test I lit a full Weber Chimney with Kingsford Competition and waited until the briquettes were all white rather than the Minion Method I normally use and this made no difference. The temperature starts at 300+ degrees when closing everything up then slowly decreases to under 200 degrees and stays there.

I can't believe a 10 cfm fan is not enough on a 18” WSM, I see a lot of people using a 5 cfm fan. Does anybody think going to a 20 cfm fan is the answer?
Would this fan be an option http://www.mouser.com/Search/Refine.aspx?Keyword=THA0412AD
It has a pwm lead. Would it work without connecting the pwm lead. Does the pwm lead need to go to +12vdc or ground to operate in a 2 wire circuit ?
Also this fan draws considerable more current than the stock Delta EFB0412VHD fan, can the HeaterMeter handle the increased current?
I run a 2 amp 12vdc power pack for the HeaterMeter.

Also all the PID, fan and damper settings are very confusing. Any good tutorials or setting examples of nicely operating systems available? Any help or ideas would be greatly appreciated.

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What does "many holes" mean as how many and what size are they?
Here's my settings I use on my WSM22.5 with copper burner under charcoal grate, 3/4" copper with Rotodamper.
B=0; P=4; I=0.02; D=5
Fan pulse; min 10%; max 30%; max at startup
Servo 700 - 2110 inverted
 
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Thanks for the reply and info Dave.

My 3/4" copper manifold sits just under the charcoal grate and is [-] shaped and has sixteen 3/16" holes. Since I removed the manifold and just ran the 3/4" pipe directly into the charcoal bowl under the charcoal grate I thought I might have eliminated the manifold and possible too small hole back pressure problem, but that didn't change the low temp problem.

This is really driving me crazy. Before I added the BBQgaskets.com gasket kit and the Cajun Bandit door I had just the opposite problem. With the charcoal bowl vents closed, Fan on above 99%, min 0% and max at 5% and the MicroDamper fan off and damper closed my pit temperature would never get below 265 degrees.

Do you open the vents on the charcoal bowl at all and what is "B=0" and where is it located in the settings?
 
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A fan doesn't do well pushing air through a restricted area, a blower is more suited for that job. For most low and slow cooking a big enough servo damper feeding through a large enough opening will allow enough convection flow to control the pit and achieve temp without a fan/blower, but if you are trying to push air through small openings you need pressure and a blower will do that job much better than a fan.
It sounds like since you have sealed of your grill you have no problem holding the temp down, so you might not need a damper at all. If you have the original HM blower you might try putting that blower on the end of your manifold tube and see how that works out for you (without a damper). I ran my bullet smoker like this with the original "air-burner" and had great results.
 
Thanks for the reply Dave and Ralph.

That makes a lot of sense to me Ralph. A squirrel cage blower might be much better at dealing with back pressure and supplying combustion air through my 3/4" pipe into the manifold (air burner) in my 18.5" WSM than the fan in the MicroDamper with my particular set up. I did receive the stock blower with my purchase of the HeaterMeter kit, I just have to locate it. :confused: From some of your earlier posts it looks pretty simple to take a 3/4" pipe fitting and hammer the end square to interface with the output port of the blower. I am excited to try that and will report back my findings. As you said I might not even need a damper to get temperatures under control, and if it does turn out that I could benefit from a damper maybe a RD3 would be a great option.

Dave I have visited your fair city a number of times from Sandusky Ohio via the MV Pelee Islander Ferry. We really enjoyed your city.
 
Yah, you can square off a 3/4" copper pipe pretty easily... I know it will fit into the old (60mm) blower perfectly but not sure about the newer (50mm) blower, I haven't tried that. Here is a pic of my first grill adapter that I made to connect the blower directly to my grill. I'm trying to remember how I made it, been a long time, I think it was with a hammer and a vice.
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Here is a pic of my "air burner" in the burn plate of my bullet smoker. I used one of those flexible copper pipes here (made for water heater connections), it hammered out square very easily as well. This setup works wonderfully without any damper...

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I agree that a fan is not a blower. For grins you might try propping your lid just a little ( like on a skewer or something ) and see if that doesn't allow to flow out a little better.

I find with my 22" wsm that when the blower kicks on, the smoke pours out of just about everywhere and drops to TBS out the top vent when off. Than again I think I was using the 20cfu blower - I really got to do a better job of labeling them...
 
wow, Wow, WOW. I found the BFB0512VHD blower that came with my HeaterMeter kit. I replaced the MicroDamper with the blower and did a quick 3 hour cook tonight of a couple meatloafs and a couple fatties to check everything out.

This is how I temporarily rigged up the blower to a 3/4" 45deg elbow with painters tape. I flattened the end of the elbow with hammer and vice but the elbow is too big to fit inside the 50x50x20mm blowers rectangular output opening.

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This is the blower and 45deg elbow hooked up to the charcoal bowl.

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Here are my HeaterMeter settings. Just a guess at the settings for a first cook with the blower.

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Here is the graph of the cook. I did the modified Minion Method with about a half dozen lit briquettes, empty water pan, all bottom vents aluminum taped shut, lid vent 100% open. I am really impressed. Once the meat was added and the temperature stabilized, the pit temperature stayed at plus or minus 0.5 degrees of the 225 degree setpoint until I opened the lid later in the cook to baste the meat with bbq sauce. After the open lid recovery the temperature stayed at plus or minus 0.5 degrees of the 225 degree setpoint until the end of the cook.

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I can live with the slight overshoot on the open lid recovery unless someone has some suggestions on what to change in the configuration settings.
I think the only thing left to do is come up with some permanent way to mount the blower. Does anybody think a damper would be of any benefit besides physically attaching the blower to the 3/4" copper pipe?

Here is my setup in case someone can benefit from my configuration. I used a 7/8" metal hole saw to make the hole in the bottom of the charcoal bowl for the 3/4" copper pipe union. I can easily remove the 3/4" copper pipe air burner with the union for cleaning or whatever. Thanks everybody for the help and suggestions so far.

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Hey, great numbers Bob. Been watching your thread to see if I want to bother/attempt some type of air diffuser as you did. Looks like no damper nessasary. I would love to see the graph on a 16 hour cook.
 
Nice results! I knew a real blower would get the job done...
If you construct an "air-burner" properly, with the right size/amount of holes, there should be no need for a damper really. Seems like you nailed it, can't argue with the results. Another thing I love about the air burner setup, you can light the fire with just a tiny bit of paper, the air jets will stoke up even the smallest fire to temp.
 
Sorry I'm only just seeing this...

Yup, you need a blower for an air burner setup. The airburner is an extremely restrictive redesign. The MicroDamper utilizes an axial fan which doesn't have the "oomph" to fly through so many 90* angles and then through tiny holes. If used without the airburner you'd be just fine. Plenty of people use it on WSMs and UDSs.
 
I am another shinning example of a dummy trying to apply someones great design or product to the wrong application. I hope I didn't come across as being negative about the MicroDamper. That wasn't my intention. I should of done more research here on the forum. As I don't have a printer and didn't want to order parts, the MicroDamper Kit seemed an easy solution for me.

Bill that is next up on my schedule, a long cook with a couple Pork Butts or a Brisket. I will report back with my findings.

Thanks again Ralph for your never ending support, help and suggestions here on the Forum.
 
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I've done a couple cooks on my WSM 18.5" with HeaterMeter and blower since my last posting. Yesterday I smoked 4 whole chicken halves on the top rack without a water pan, starting with a Weber Chimney and a half of 50/50 lump and briquettes. I was able to run at 325 for an hour with the blower max at 75%, so it looks like high temp cooks are not going to be a problem in the future with my setup.

Today I did a 7 hour smoke of 2 Beef Chuck Under Blade Boneless Roasts. Modified Minion setup with a half dozen lit briquettes, cold water in the water pan, bottom vents closed, top vent opened 100%. Except for removing the lid for adding the meat, wrapping and removing the roast that finished first, the temperature held at 225 +- 3 degrees. I think I had a little more temperature variability because of the wind today.

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Seems like you've got it nailed there... The air burner setup is a really good fit for a bullet smoker, as long as you don't make too many or too large holes you shouldn't need a damper. The only drawback is wind as you noted, if it catches the blower opening just right it can stoke your fire up as if the blower was running...
 
Hello guys. I see that this thread ended 8 or 9 months ago. I want to reply, because I have had issues that are very similar to Bob O's. I posted about it a couple of times in the past few years..
I have a UDS that I was never able to stabilize. The temps were always rising or falling - requiring constant tweeking of valves. Therefore, I built a Heatermeter, and I bought a rotodamper. That minimized the tweeking, but I was still never able to control the temperature with just the damper. It would open 100%, and then the temps would start to fall. I tried using the blower in various modes, but I have not been able to find that perfect configuration that controls it well. I wish I could use the damper to control the convective airflow, but without the blower, the temps gradually fall. I can open another intake port, but then the temps climb too high.

I wonder if I need to make an airburner for the UDS? I would then use the blower?

I noticed that Bob O set his blower at 10% max. That seems very low. Maybe my blower is providing too much air? Could the air from the blower be by-passing my charcoal basket?

Any ideas?

Also, the airburner has its holes pointing up. Any problems with ash clogging it?

Where do you put your cooker/ambient temp probe? I try to keep it away from cold meat, but close enough without being in the hot air stream.

Thanks
 
My UDS is very stable. What do you have for a inlet and exhaust. I don't recommend a stock blower for an UDS, as it needs at least a 8.6cfm and the stock is 6.7cfm. I use a rd25 which is a larger rd3 and has a 28cfm blower.

My system

Weber grill top(always open, I never change)

1 inch inlet with a ball valve. You may need extra inlets covered with magnets, sometimes they are helpful to get some extra air in quickly or on very cold days.

Lump charcoal my basket is a Weber charcoal grate wrapped with expanded metal, it can hold about 20 pounds or so.

Always light 1/4 charcoal starter

I usually just use the stock PID settings, sometimes I adjust the I(could be the D, i can never remember, lol) something like .002 to keep the blower from staying on when it it gets close to the set point.

What I did is learn to use the UDS without trying to control it with the heatermeter. Learn were your UDS is stable. Must have a ball valve 100%

Start some lump and see where your UDS temp stabilizes, if it goes over 300, then you probably have some issue with air getting into the UDS and it will need to be fixed. Most likely it will stabilize around 250 or so. Once it stabilizes go to next step

Take the ball valve and close it 25% and let it slowly come down in temp, let it stabilize and record the temp.

Repeat the above until you get the temp to stabilize to around 220°

Once its stabilizes at 220, that's where you keep the ball valve while you use the UDS and your heatermeter and blower. That way, the heatermeter will be in control of the uds at higher temps and if the blower should stop or malfunction, your uds won't have any safety issues either.

I can start my UDS and get it ready for smoking with 10 minutes or so of lighting it. There are some days though, I do have problems, but I usually just adjust the ball valve a little to overcome weather effects.

I hope this helps, Pm me if you like a rd25, I can print in any color you may prefer
 
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Thank-you very much John for the reply. I am not sure I have ever run my UDS without meat. I need to run your stabilization test.

When you cook, do you put some type of diffuser above the basket? I use foil on the first grate (one 12" wide strip) to make the hot air go up the sides and not directly up under the meat.

I have 3 inlets: one 3/4", and two 1". I have a ball valve on one of the 1" inlets. I keep the other 2 capped unless I need them.

I also use a charcoal basket that I made from a Weber charcoal grate.

When you run the test, does it matter how much of the basket is filled? Do you fill with unlit, and then dump 1/4 chimney on top?

I probably won't be able to run the test for a week or more, so I apologize in advance if I don't report back soon.

Thanks
 
I have never used a diffuser. I usually have a full basket, then I just keep using it until I need to add more. I only light the chimney
 
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