UDS not holding heat!

[pritchardhallhokie]

Hello Everyone,

This is my first post, I've been a long time reader but just signed up recently and have a burning question and I'm hoping someone can help.

I have made a UDS with a food grade barrel. I have done two burns with charcoal to try to dial in the heat to ensure I'm going to be able to do a long cook with a balanced temp.

So, here's my problem after both attempts: I can't hold temperature. To be more specific, I can get the heat up to 400 but then when I close things off, it drops below 200, and will stay there all night. I have a 3.5" hole in the top (unscrewed) and I drilled 5 holes in the bottom about 2 inches above the bottom. Each hole is drilled with a 3/4" bit. I am using magnets to close off the holes at the bottom. I made a charcoal basket out of cement reinforcement mesh to save cost and put in 15 lbs of charcoal and light it with a weed burner. Once I light it, I leave the top off and get the heat up to about 300 and then put on the top and keep the valves open at the bottom. Once I get the coals going, I can't get the temp to stay stabilized and it continues to drop.

My biggest questions are, what is a healthy ratio of intake to out take to ensure good temp? And also, what would your first thought be as to why I'm losing heat?

Thanks so much for all your help!

[Bludawg]

How far off the bottom of the drum is the bottom of the the coal basket?It sounds to me as if you have an intake air flow problem. I run 3 intakes and a 2" exhaust the bottom of the basket is 3" off the bottom. I never had a problem keeping my temp. I catch it on the way up instead of letting it run wild and trying to tame it down.

[pritchardhallhokie]

That's my biggest fear. But, I have three carriage bolts in the bottom of the basket which are 3" tall. So, at the most the basket is 3" off the bottom of the barrel.

Any other ideas? BTW, thanks so much for responding so fast!

[tburda]

Ok, first, welcome. Second Hi everyone who hasnt seen me in a solid year or so. Life happens and you got chit to deal with. Dealt with, and I'm back.

Now, have you read the UDS thread to see the methods that have proved to be most successful, because judging from your post, you have not. I don't imply you have to read all multiple hundred pages, though I did, and when I have trouble with my UDS I know EXACTLY what it is.

3.5" exhaust is pretty big, most of us run 2".

Intake, 3, 3/4" inlets. All 3 open to fire it up, and two closed one adjusted as needed to dial it in. I generally run 1/2 open ball valve on one 3/4" intake and that keeps me in the neighborhood of 250 +/- 10 degrees.

Do you have legs on your charcoal basket? The basket needs to be elevated off the bottom of the drum for ash to fall through and air to get up. That being said, what material is that mesh made of? Zinc is toxic so make sure it's not that. There is a reason we use the materials we use, though they arent the cheapest available.

Have you looked into the burn methods that we use on the UDS? I personally use a minion burn, with great success. If you're not familiar, thats filling your charcoal basket to the capacity needed (you'll dial that in as time goes on) and lighting about 3/4 to 5/8 of a charcoal chimney red hot with charcoal then dumping on top of the basket and letting it burn down.

Next, PATIENCE. I try to stick to a 30 minute timeframe. Checking the temp 30 minutes after an adjustment. You will fight that intake open closed open closed all day/night if you cant be patient and let it level out.

And finally, ambient weather. Ambient temp, and wind are major factors when using a UDS. If it's pretty cold out, it'll knock down that temp pretty fast and you'll have to run with a more open intake and burn more charcoal faster. If it's windy, you have to take into account the direction of your exhaust and intake. You can create a vacuum in the uds basically if the wind is fast enough in the right diretion. It's wisest to have your intake facing away from the wind. I had my intake 90 degrees to the wind once and it completely extinguished my burn in a matter of a couple hours. Ruined a 30 dollar brisket. I hope the information helps you to narrow down where your problem is.

[cheapbeer]

what are you using for a thermometer? perhaps you are not getting a good reading. I have used the barrel lid with both plugs out and weber lids with the daisy wheel open. I use 1/2 pipe nipples and usually only have one open on my favorite uds and the newest uses a 3/4 intake with the valve in addition to the 1/2 nipples. I start off with a few open nipples, top on and i let it get up to 250 then close all but one nipple. they both settle in real well around 230/240 this way. When I add the meat it cools off some and I open it up a bit and then close it back to one open as the temp is coming up and it settles right back in. It doesnt take much air for it to run smooth. Lump charcoal, if you are using briquettes and getting it hot then shutting it down maybe it is ashing over the coals and choking itself? work with it and you will figure it out.

[pritchardhallhokie]

Hello. Thanks for all of the quick responses! I'm using a replacement grill thermometer for the UDS.

My basket sits about 3" above the bottom of the barrel.

I just can't think what's causing this trouble.

[Ye Olde Party Palace]

Just as a note, my uds has 3-one inch pipe nipple intakes(2 w/ caps, 1 w/ ball valvle) and a 2 inch exhaust. I start my fire basket with about a half chimney of hot coals and all pipe nipples open. As the temps go above my desired temp, I start shutting off pipe nipples(usually the 2 / caps), leaving the ball valve fully open. I then adjust the ball valve as needed, and open on of the capped pipe nipples if necessary. Usually, my uds cruises at about 250 degrees with 2 nipples capped and the ball valve 2/3 open. I use a digital thermometer, which makes life a whole lot easier. Once that I have the drum on cruise, it is just a matter of tweaking the ball valve to dial in the temp that I want. Hope that this helps you somewhat.

[tburda]

I also use a combination of thermometers. I use a 12" turkey fryer thermometer inserted into the side of the drum 1/2" below the grate, AND a digital wireless in a potato sat on the grate from time to time to be sure my $2.99 thermometer is still accurate.

[Outnumbered]

Try closing off the top vents as suggested above. It sounds to me like you're letting too much out the top. Not sure you need 5 intakes at the bottom either, but that should lose heat.

[willbird]

Also you said you leave the top off until you get some temperature ?? I never leave the top off when doing anything with a UDS....when the top is off it is an uncontrolled burn that usually leads to a temp spike when the lid is replaced.

Another thing with lump......you need to get it tight together, the first few times I just dumped in the basket and got uneven burning...now I just shake the basket while twisting it to settle the chunks together.

A couple pictures of the whole rig might be worth a few thousand words of description :-).

If I had to guess it would be that the intake holes being up that far from the bottom is the problem, but I'm an utter noob at UDS construction myself, in my limited experience too much exhaust (poor fitting dome lid) the temp ran away hot.

Bill

[Just BS]

No two UDS's are the same. They're all built a little differently with different materials. The one thing they have in common is that they take about a half dozen cooks to settle down and get figured out.

As suggested read the UDS Thread. At least go back a few pages and start following it. The learning curve is steep and you'll catch on fast.

As also stated, catch the temps on the way up. It happpens fast. Sart your coals and PUT THE LID ON. Start shutting down your intakes as you approach your desired temp. For me, one 3/4" intake open with approx 2" exhaust will run in the 225 range.

A good digital thermometer is worth is weight in gold. Check out the ET-732. It has changed the way I BBQ.

Good luck!

[jrn]

Hello. If your shutting all your intakes and exhaust, and its not snuffing the charcoal, then it's pulling air in somewhere. I've got 3 intakes that are 2" up from bottom of barrel. They use 3/4" close nipples, 2 w/pipe caps and 1 ball valve. As far as exhaust goes, I'm using a weber lid. I can close all intakes and the smoke coming from the exhaust immediately starts dying. Then once exhaust is shut it goes out reasonably quick.

I've been amazed at how well mine will hold a steady temp. That's with briquettes or lump. These things are awesome!

Btw, you got the liner out, right?

Jason :)

[Skidder]

I'm not trying to sound harsh but it seems that when anyone makes a UDS and deviates from the simple kiss method (keep it simple stupid) and then has problems they always wonder why. You say you have a 3.5" exhaust. K.i.s.s. method calls for 2" or eight 1/2" lid holes. Intake you say five 3/4". K.i.s.s. is three 3/4" holes for 1" nipples. And when you start your fire you bring it up past 300. The k.is.s. method calls for catching the temp on the way up not trying to bring it down to stabilize your temps. Hope this helps some. Look at one of my last ones I built. Yes it has a lot of little add ons but if you look close it's still a k.i.s.s. UDS. 2" exhaust with three 3/4" intakes. I'm on build #15 coming up this week and everyone of them has run perfectly because I don't drift from the k.i.s.s. method.

[PorkQPine]

I am not sure why you are bringing the temp up to 400 and then shutting down the intakes. It is very hard to bring temps down so bring the temp up slowly and not over fire the UDS. I am a bit anal so I use a DigiQ and never have to worry about temps. I light a few lumps in the chimney and dump them on the basket full of lump and put on the lid. When temps stabalize, about 1/2 hour I put on the meat and that's it until they are done.

[Bludawg]

Originally Posted by Skidder

I'm not trying to sound harsh but it seems that when anyone makes a UDS and deviates from the simple kiss method (keep it simple stupid) and then has problems they always wonder why. You say you have a 3.5" exhaust. K.i.s.s. method calls for 2" or eight 1/2" lid holes. Intake you say five 3/4". K.i.s.s. is three 3/4" holes for 1" nipples. And when you start your fire you bring it up past 300. The k.is.s. method calls for catching the temp on the way up not trying to bring it down to stabilize your temps. Hope this helps some. Look at one of my last ones I built. Yes it has a lot of little add ons but if you look close it's still a k.i.s.s. UDS. 2" exhaust with three 3/4" intakes. I'm on build #15 coming up this week and everyone of them has run perfectly because I don't drift from the k.i.s.s. method.

That is a great picture. I can imagine lying it that hammock listening to the waves against the shore with the smell of hickory smoke in the air. Man you live good