WSM 18.5 temp control.

Discussion in 'Charcoal Smokers' started by rich t, Jan 31, 2016.

  1. rich t

    rich t Newbie

    I am hoping that some folks that post here can provide a few tips on how to regulate the temp at 225 degrees for "low and slow".
  2. dward51

    dward51 Master of the Pit OTBS Member

    If you are just starting out with a WSM, stick with the water pan and put water in it.  It serves two purposes, 1) it acts as a heat moderator and 2) it helps keep the chamber moist (#1 is the most important).  Also the upside down dome shape funnels the main heat flow up the outer edges of the cook chamber for indirect heat, which is what you want for "low and slow".

    Temp control is all about controlling any one of the 3 things needed for combustion (fire). 1) fuel (the charcoal); 2) oxygen (air through the vents), and 3) heat (the lit coals that start the process).  Take away any one of them and the fire goes out.  On the other hand you can restrict or fan any one of these to decrease or increase heat (pit control).

    Do not fire up a ton of charcoal.  It depends on what you are smoking and how long you are going to need heat as to how you load the charcoal ring.  For a smoke lasting 4 to 6 hours, just fill the ring about 1/4 to 1/3 full with unlit charcoal with a few chunks of whatever smoke wood you want to used (fist sized chunks are good, no bark).  Then start about 1/2 a chimney of lit.  Once the lit is good and ready, pour it over the unlit and spread it out evenly.

    If you are doing along smoke like a couple of pork shoulders overnight, then the fire ring needs to be packed to the brim.  You still only use a single layer of coals to light it, and depending on conditions on a 18 to 22 hour smoke, you may need to add more charcoal at some point.  If you are just starting out (based on your question, I assume you are), stick to shorter 4 to 6 hours smokes until you get the hang of temp control by using the vents.

    The top vent is always 100% open on a WSM when smoking/cooking.  You control the airflow with the bottom vents.  Also keep the charcoal access door closed as when you open it, you dump in a lot of fresh air and the temps will climb.  I never use my charcoal door.  At the start of the smoke, close all the bottom vents until they are only 10 to 15% open.  Let the pit settle in at that setting for at least 15 minutes.  If it's falling below 225*, then slightly crack at least one vent open a little more and wait another 10-15 minutes.  If it's still too hot and the temp is not falling, close one or two of the bottom vents (not all of them).  If the temp is still falling, leave the vents alone and give it another 10 minutes and recheck.  It should settle in on a solid temp and stay there.

    Once the pit is stable, then add the food to be smoked.  You will get a temp drop right after adding the food as you just pit in a cold mass.  It should climb back up and re-stabilize in 15 minutes.  Depending on how much meat you are adding, you may need to do the fine tuning of the lower vents again.  Once you find a sweet spot leave it alone.  Remember it does not have to be exactly 225* to be low and slow.  That is generally a range of 215 to 250* and the only difference is at 250* it will be done a little sooner. It will still have the same flavor as 225*

    The trick is not to get caught up into "chasing" a temperature.  Everything you do changes a variable which affect the pit temp.  Open a vent a little, it gives more air to the charcoal and it starts to burn a little hotter, open it too much and you overshoot, then the natural tendency is to close it a good bit to compensate. Next thing you know, you are "chasing" a moving target as the temps are like a yo-yo.  The trick is to adjust something, and wait.  Let the pit settle back in before making any real adjustments.

    After a couple of smokes you will know the pit and how a certain load of food performs.  Next thing you know, you are dialing it in and not having to touch it after the coals are loaded.   And if you want to get as close to fire and forget with a WSM get a power draft like a BBQ Guru.  But learn the vents the old school way first. 
    Last edited: Jan 31, 2016
  3. smokinal

    smokinal Smoking Guru Staff Member Moderator OTBS Member ★ Lifetime Premier ★

    Well said Dave!!


  4. rich t

    rich t Newbie

    Thanks Dave.  That is exactly the type of feed back I was hoping to get.  I did a dry run yesterday with a fill load of fuel (just to check burn time for longer cooks).  I did find myself chasing that temp yo-yo.

    That tip about leaving the top vent full open and making air flow changes only with the bottom vents makes a lot of sense now that I think about it.  Since I am new to smoking I have been checking multiple sources for information and I have found that there is a very active debate about what goes in the water pan.  Some stick with the water, others swear that sand or clay briquettes are the way to go.  Some merely wrap it in foil and use it to redirect the heat.

    I was poking around on line last night and case across the BBQ Guru that you mentioned.  Seems like a nice tool, but a bit pricey.  I will mostly be just smoking for my wife and myself with the occasional back yard BBQ with family and friends.

    Thanks for taking the time to respond to my query.  I have always wanted a smoker and I finally got around to getting one.  I want it to be an enjoyable experience and not end up frustrated out of ignorance and not use it.
  5. dward51

    dward51 Master of the Pit OTBS Member

    Water in the pan, sand in the pan, clay flower pot base, etc... all serve the same main purpose.  They are thermal masses that moderate temp swings in a WSM.  Water has some other qualities so I'll address it first.

    Water, unlike the other things people put in their pans, can phase change in the smoking environment.  What I mean by that, is if you heat water over 212*, it starts to convert to steam.  There is a unique quality about this.  And that is it takes a rather large jump in energy (energy put into or absorbed by the water) to change from liquid water at 212* to steam at 213*.  On the flip side, steam wants to  naturally drop back to liquid water in that same 1* temp range.  But like the jump in energy to flash water to steam, it also sucks energy out of the air as steam drops back to water.  So in addition to serving as a thermal mass, water in a smoker is "happiest" at that magic range of where smoking begins.

    A thermal mass tends to hold heat.  Let the temp drop, and it will start to radiate heat slowly, let the temp rise and it will absorb heat slowly.  Think of a brick wall that has been in the sun all day.  It stays warm to the touch for hours after sundown. This is an example of thermal mass. The result is a thermal mass (any mass, water, sand, clay flower pot base, etc....) will slow the temp swings in a WSM, both up and down.  If you want to try an experiment, run the WSM with nothing in the water pan (leave the pan in to cause the air to flow to the outer edges like normal).  You will play hell chasing the temp swings with nothing to moderate the changes.

    Water has the combination of both thermal mass and that magic quality of the liquid to steam point being so close to the smoking temp of 225*, so it is the perfect medium to learn how to tune a WSM as it is more forgiving.  It does add some moisture to the air in the pit, but I doubt it really matters.  The main benefit is it makes temp control easier and helping prevent a run-a-way pit with higher temps.

    Once you get the hang of controlling temps with water in the pan, you can try switching to a clay flower pot base.  The clay pot base will let your fuel burn longer.  The reason for this is you are not dealing with the water sucking energy out of the air as the steam drops back to moisture in the air.  That jump from liquid to steam at 212-213* is also the reason you use more fuel when smoking at 225*.  It's not a huge difference, but there is science behind it.

    Another quirk of a thermal mass like the clay flower pot base or sand is it moderates to a point.  Once the mass is at the pit temp, it does nothing to help slow the increase of temp (where water would due to the steam to water droplets phase change sucking energy out of the air flow).  A pit with a solid mass like a clay flower pot or a pan full of sand will run over the set temp and take longer to drop back down after the fire level is under control.  This is due to the thermal slowly releasing that energy.  So you need to understand vent control to keep a solid mass moderated pit from starting to run over temp in the first place.  This is why water is more forgiving.  A solid mass give the benefit of moderating temp swings when you open the dome to add meat, brush with sauce, or whatever (but remember, "if you are looking, you are not cooking", so leave the dome closed unless there is some part of the smoke that needs to be performed).

    As to the BBQ Guru (or any other brand of "power draft"), you basically close all the vents except for one hole in one vent.  A computer uses a temp probe in the pit at grate level to control all the air flowing to the charcoal for total control of the pit temps.  It is basically a set it and forget it sort of thing if all is set up correctly.  A WSM with a power draft is a wonderful smoking machine!!!!  Especially when you are doing a 18-22 hour overnight smoke.  No sitting up all night watching for temp swings and adjusting vents as your fuel level drops.  With a power draft, if you have fuel, it will hold the set temp. Once you use one, you will never look back.  They are worth the expense IMO.  But there is no reason you absolutely have to have one to enjoy a WSM.  It is a fine smoker in it's own right.
    Last edited: Feb 1, 2016
  6. rich t

    rich t Newbie

    Thanks again Dave.  I will certainly put your advise to good use on my WSM.  I will probably end up buying power draft at some point, but I want to go old school until I can hold temperature manually.  I don't want to be so dependent on a power draft that I ruin some good meat if the unit dies half way through the cook time.

    What are your thoughts or experience with the Minion method of loading fuel?
  7. dward51

    dward51 Master of the Pit OTBS Member

    The "standard method" of firing a WSM is dump a chimney of lit charcoal in the fire ring, spread it out, add smoke wood chunks and top with unlit charcoal. I never go this route.

    The "minion method" is the opposite.  It's basically what I described in my first reply.  Jim Minion came up with this method which consists of a volume of unlit charcoal on the bottom, some wood chunks at the top and then top with a thin layer (or even a thin spot) of lit for a slower more controlled fire.  I suggest going with this method.

    Another variation of the minion method is to use a tin can with the top and bottom cut off.  Put it in the center of the fire ring.  Put some smoke chunks beside the can and then fill the ring around the can with unlit charcoal.  Pour your small sample of lit charcoal in the tin can then use tongs or pliers to slide the can out of the smoker.  You end up with a small cylinder of lit surrounded by unlit and smoke wood.

    There is another version I think of as the "snake" version.  You lay a ring of unlit around 80% of the outside edge of the fire ring. You do not have charcoal in the middle of the fire ring.  Then put a small collection of lit charcoal on one end of the "snake".  It will burn slowly around the ring.   This is good for a 6 hour cook on average, where with the other two versions you can go longer depending on how much unlit you use.  If going with the regular minion or the tin can minion and you only want a 6 hour burn time, don't fill the fire ring fully with charcoal.  A full ring with good air flow control in a 18.5" WSM "can" run up to 18 hours (but the conditions need to be right).  But I'm more comfortable with 12 hours on a full ring in the 18.5".

    Here is another plus for the minion method.  You have lit on top of unlit, so any smoke given off by the unlit as it starts to burn, will flow over and past the red hot coals.  Think about the acrid smell of the white smoke of charcoal as it starts to light in the chimney.  IMO that is partially burned up as it flows over the lit coals in the minion method.  Where as with the unlit over lit (standard method of lighting WSM), you have the white acrid smoke with a free path into the smoke chamber.  Yes, it will stop after a while, but I prefer to avoid it in the first place.  Lit over unlit does just that.

    If you ever do an overnight smoke and find you have to add charcoal, and put the unlit on top of what is left in the bottom of the fire ring, you will see what I'm talking about.  The catch 22 is if you light a full chimney and dump it in for the reload, you temp will be way over what you want.   On a 20 hour smoke where I find I need to add charcoal, I will pull the body of the smoker (middle section, grates and dome all as one unit, just lift with welding gloves on your hands, even easier if you have added side handles).  Then I shake the ash off the grate into the bottom (I have my fire ring wired to two fire grates at 90* angles so it holds smaller lit coals).  Then I will use a small metal ash shovel to gather up the remaining lit.  I will either push them into a lump one side or put them in a metal container (which is insulated against the deck as the metal will become hot real quick and scorch wood).  Then I dump in the unlit and top with the lit from the container.  In essence I'm reloading with the minion method again.  But on a short cook of up to 10 or 12 hours you can just vary the amount of unlit in the bottom of the ring to get the time you need and should not have to reload.

    It just dawned on me, but I'm not sure what size WSM you have.  The 22.5" will work the same way, but due to the larger volume of air to heat, it burns through fuel faster than a 18.5" WSM.  Mine is a 18.5" of the old design (had it since 2005).  All the principals are the same, it's just a bigger pit uses more fuel.

    I know the forum owner does not like linking to outside forums, so I will not post a link but there is another forum that is dedicated to the WSM models.  Lots of good info there, photos on how to do stuff, and lots of mods people have come up with over the years.  Just google for "The Virtual Weber Bullet".  That takes you to their main page with info on the WSM's and there is link to the forum there as well. This is a must visit site for any WSM owner.  (Hopefully I won't get banned for helping a brother out with this info).
    Last edited: Feb 1, 2016
    lemmysc and rich t like this.
  8. dirtsailor2003

    dirtsailor2003 Smoking Guru OTBS Member

    I'll throw in my two cents on how I run and light all of my charcoal smokers, bbqs. Once you figure it out it's very simple and temp swings a re minimal and normally caused by weather conditions, not what's going on in the pit. I smoke year round and in all kinds of weather. During the winter it can be single digit temps, during the summer triple digit temps. Wind is probably the worst enemy you can have. So shielding the lower vents from gusts is important to maintaining consistent temps. A simple screen of plywood can work. Because of our cold climate I use Refletix insulation. I form a circle around the smoker (2"-3" gap between the insulation and the smoker.

    I will mention I do not use water or sand in my water pan for me 18.5, or any of my smokers. I wrap it with foil for easy clean up.

    For my WSM 18.5, and my mini-WSM's is fill the charcoal basket/ring full. Depending on the length of the cook I will add (2-6) 2"-3" hunks of smoke wood also. Put the body and lid on and open all the vents wide open. Then I light a propane torch and insert it into one of the lower vents. I allow the torch to run until my therm shows the pit temp to be 25-30 degrees above my targeted temp. I turn off the torch and remove it. The temp is going to drop considerably. If it drops more than 20 degrees below my targeted pit temp I torch again. I'll do this step until I am about 15 degrees from my target temp. Then I let it come up by itself. If I'm doing low temp smokes I run the torch through the same vent each time. For higher temp smokes I will light through 2 of the lower vents or all three. The whole process takes 10-15 minutes to be at temp withTBS in the WSM 18.5, and 5-8 minutes in the mini-WSM.

    Using this method there is almost no waste of fuel energy as you aren't lighting and burning a chimney outside of the smoker. The torch helps preheat the smoker. There is no need to refill the smoker. I can get 12-14 hours in the mini, and over 22 hours in the 18 running 250-265 using briquettes.

    When you are done with your smoke, you close all the vents and snuff the fire. When you are ready to use again, shake off the ash, dump the ash, add new fuel to the old, torch and light.

    I really see no need for guru or other device to provide consistent temps in a WSM. Block the wind from the lower vents, make small adjustments, and being 5 degrees off one way or the other won't ruin the meat. Practice and use the KISS method, Keep it simple smoker!
    rich t likes this.
  9. drewed

    drewed Meat Mopper

    Just to beat that dead horse a little more....

    When you put that big old slab of COLD meat on, your temps are going to drop, don't go chasing it right away.  IT may recover, yet you may need to give a littler more air to it as well.
  10. rich t

    rich t Newbie

    Keep that input coming.  I am learning a lot.
  11. trueteam

    trueteam Smoke Blower

    These guys obviously know what they are talking about. The more you use it the better, all that smoky goodness builds up and will help seal the smoker. My 18.5 is very low maintenance once it settles in. I don't use anything in my pan anymore either, just foil it. Enjoy that WSM!
  12. Harry Soo uses the top vent to control his temperature. Myself, I just go with what works. I start by shutting down the bottom vents, and if that doesn't do it, then the top vent. At some point it settles down and stays there. My WSM is really good about holding a stable temperature.
  13. jirodriguez

    jirodriguez Master of the Pit OTBS Member SMF Premier Member

    Be very careful shutting the top down, if you close it and leave it closed you will develop creosote. [​IMG] It tastes nasty and then has to be scrubbed out of the inside of your smoker before you smoke anything else. I honestly would never shut my top vent less than 50%, and even then I can count on one hand the number of times I have ever closed the top vent at all.

    Rich T - also keep in mind the WSM's run hot for the first dozen or so smokes. This is due to everything being so clean! Once you develop a nice bit of residue (seasoning) on the inside it will seal up a lot of the little air gaps. This makes it much easier to control temps and improves fuel efficiency - but when just starting out damp the fire down hard at about 200°, then open up one bottom vent to about 50%. Wait about 15 min. and see where it starts to steady out at. Chances are you will only need one bottom vent open to target 250°.

    Me personally I have always done just water and the minion method on my 22.5" WSM. With that set up I can get 18+ hrs burn time in the winter and 22+ hrs in the summer - please note in the winter I wrap mine with a welding blanket to keep the wind off of it so that helps a LOT! I have had my 22.5" WSM since 2009 and it has never let down yet, it just plain works without much input from me.

    rich t likes this.
  14. trueteam

    trueteam Smoke Blower

    For what it's worth, I have never touched the top vent on either of mine
  15. rich t

    rich t Newbie

    Thanks folks.

    I'll do a few more dry runs without food to get a feel for the low and slow.  I smoked a chicken last night that came out fairly decent.  Didn't have quite enough charcoal in the WSM to hold the temp at 325 for the time needed so I had to finish it off in the oven, but that smoke flavor from the apple wood I used was awesome.  I dry brined with salt about 4 hours before the cook and used Meathead's Memphis Dust for the rest of the seasoning.
  16. rich t

    rich t Newbie

    I was thinking about getting a water heater blanket for winter cooking.  Never even thought of a welding blanket.
    Last edited: Feb 2, 2016
  17. trueteam

    trueteam Smoke Blower

    IMHO I wouldn't run it without food, I view that as a waste of fuel. Throw a butt or a chuckle. Very forgiving cuts and you end up with food for your efforts. And as for chicken, I can't get my WSM that hot, she wants to run lower. I could mess with the door but don't want to. I don't care about the skin so 275 is fine with me. If I have skin eaters I do it on the kettle indirect or break out the rotisserie.
  18. trueteam

    trueteam Smoke Blower

    Sorry, throw a butt or a chuck roast on, damn spell check
  19. redt

    redt Fire Starter

    Thanks, RichT for starting this thread, and Dave. dwschenk, trueteam, JIRodriguez, and everyone else for providing more info! As a new 18.5 WSM user, I've tried several methods with some degree of success, but still find myself "chasing the temps". Your explanations will help a lot!  Thanks again!  
  20. drewed

    drewed Meat Mopper

    A chuckle is a great thing to smoke!  lol
    Honestly its just meat.  Temp doesn't have to be that exact.  People who brag about +-5 degrees are way to anal anyway ( me included! )  Just keep it in the neighborhood and you will be fine.  Cook at 300 rather than 225, guess what?  Meat got done sooner, but it still tasted good.  Slogged along at 195, that will work too, but may take a real long time....
    Its BBQ, not rocket science ( although a few bottle rockets have been launched from the weber.....) Enjoy the smoke, don't make it work.

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