UDS consistent temp. Need help, opinions, etc.

[William89]

Ok so here's the details. Built a UDS, running three 3/4 inch intakes. One of them with a ball valve to control temp. Exhaust is a 2inch pipe 6 inches long. No water pan or heat deflector.

After the build I did a dry run of about 15 hours. Was very impressed with it. Ran at 275° with 2 intakes shut and the ball valve open. After that I cooked a pork loin and it ran the same way. Now since then it has been completely different to get it to hold 275°. I have done ribs, brisket, chicken thighs, and beef ribs. Every cook the smoker now has to run all of the intakes open and the ball valve 3/4 of the way open... The outside temp around here has been consistently between 85-90° so Im not sure why the sudden change to run 275. I've been running the same royal oak briquette charcoal too.

Normally I wouldn't worry too much but with winter on it's way I'm concerned I will not be able to run temp with the cold illinois winter's. Anyone with any ideas what I might have going on here would be greatly appreciated. Thanks

 

[daveomak]

Change to 1/2" ball valve... and 1/2" nipples... Check to make sure the lid seals air tight... If the exhaust will not allow adequate air flow for higher temps during the winter, drill 1" holes around the top sides of the drum... 6-8 should work and then you can plug the 2" bung in the lid... evenly spaced holes around the top of the sides of the drum provide even exhaust for even heating.. they can be plugged with electrical plugs if you drill the holes the correct size... use a step drill for drilling the holes..

 

[William89]

Ok thanks for the reply and the info. So you think smaller intake and more exhaust will help.

 

[daveomak]

3/4" vs 1/2".... 3/4" = 2X the area... 1/2" allows for a more delicate control... You need enough exhaust as to not constrict the air intakes... remember, the air expands as it is heated so area intakes vs. heated exhaust is not a direct correlation...

 

[Bummed]

I too have 3 - 3/4" intakes with 1 ball valve and also a 2" x 6" exhaust, mine runs at 275 with just the one ball valve open. It's always hot here in South Alabama and it stays right there at 275. If I open all the intakes she gets up over 325.

 

[hardcookin]

Just a thought...Do you have damp charcoal?

Also how high is your charcoal basket off the bottom of the drum?

 

[William89]

Charcoal bastket sits 4 inches from the bottom of the drum. Intakes are 3 inches from bottom. I usually buy charcoal 7 or 8 bags at a time. I keep them in the garage. Ive questioned if I'm starting off with enough lit coals. Usually put 10 lit coals on the basket.

 

[hardcookin]

When you are done smoking,do you empty your charcoal basket? Or just add more charcoal to the basket for the next smoke?

 

[William89]

Add more. I will take charcoal basket out and shake it to remove any small pieces and Fill what's left with new charcoal

 

[daveomak]

Your UDS does not have enough exhaust...

 

[pc farmer]

Your UDS does not have enough exhaust...

This guy is right. I had 4 3/4 inch holes for exhaust. Didnt work so i added 4 more. Works great now.

 

[William89]

Thanks everyone for the input. I'll be sure to do some changes and more cooks before the cold weather hits!

 

[SmokinLogs]

I know this post is a little old, but how did it turn out? I’ve got a similar setup: 3-3/4 intakes, 2 inch exhaust with 6 inch riser. I was having some issues. The first of which was a bad thermometer that I thought was good. I’ve got my uds working pretty good, but I think I might still need more exhaust. Just curious what worked for you?

 

[daveomak]

This guy is right. I had 4 3/4 inch holes for exhaust. Didnt work so i added 4 more. Works great now.

 

[William89]

I followed daveomacks advice and added more exhaust. Worked like a charm. I added another 2 inch exhaust pipe and it runs great. Only other thing I've had to do was add a heat diffuser (pizza pan with holes) after noticing my temp gauge on the barrel and a grate thermometer in the middle were about 80 degrees off. Since then it's performed just right... Good luck and hope ya found all the answers ya need.

 

[SmokinLogs]

Daveomak, took your advice. Worked pretty good. With 2 ball valves open, and one closed I was holding steady about 225. I had an extra drum lid I found while getting the parts together for my UDS build. I figured it was worth cutting some holes in to do some experimenting. I’m glad I did. Thanks for the help guys.