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View Full Version : Open lid = temp spike ??


Highcal
07-28-2014, 02:07 AM
Everything I've read here mentions when you open the lid of a UDS the temps will spike up. My 30gal. UDS does the opposite, what gives ????

scrub puller
07-28-2014, 05:47 AM
Yair . . . Highcal. I hear you, I noticed the same affect.

I believe the theory is that the influx of air from the open drum stirs the fire and causes the spike.

The first few UDS's I built didn't spike at all . . . and then I did away with all the risers and ball-valve carry on and put in some decent airflow and now I have to shut the vents a few minutes before opening or I have an inferno down below.

Suggest you get more air into the drum . . . I find I can get it hotter quicker and the control is more positive.

Cheers.

Sweat'in Pig
07-28-2014, 06:56 AM
Are you going by grate temp? I always put a temp probe on the grate, and the temp will drop when i remove the lid. I beleve it's from the fresh air going over the probe. But at the same time had a fire flare-up. The fire will get hotter but the temp will read lower... hope this makes sense.

aawa
07-28-2014, 07:28 AM
The thermometer will go down, but your fire gets bigger. Once you put the lid back on though, you have trapped all the oxygen that entered the UDS from the top. This oxygen will burn off quickly and raise the temperature inside your UDS because the fire will get bigger.

Bludawg
07-28-2014, 09:21 AM
In the 8 or so yrs I have been cookin on mine I have never had that issue but then I don't leave the lid off and run to the store for a 12 pack either. My usual open time is 1-2 min and I normally loose heat as much as 50 deg during that time. I don't close anything and the temps recover in 4-5 min

Highcal
07-28-2014, 09:30 AM
Scrub, I have no risers, I have three 3/4" nipples and one 3/4" ball valve, I would think its getting plenty air intake, no ?

The temp drops immediately after removing the lid(weber dome) which makes sense as said the cool air drops into the drum onto the probe and but the temp stays down for a while after putting the lid back on. I was doing two dozen chicken drumsticks on a hanging rack and was at around 325F before lid removal, and it dropped to around 255F and took around 20 min before I got the temp back up to where it was.

Could the chill from the chicken reduce the probe temp ?? I heard people here mention that happens with big hunks of meat, but could 24 drumsticks have the same effect ?? The chicken came directly from the fridge into the drum.

jham0077
07-28-2014, 09:41 AM
That's alot of chicken, I think it would make a difference. Mine only spikes if the lid is off for more than a minute or so. If I lift it for for a few seconds to sauce, no spike. But I am still chasing temps on mine also cause I'm still learning.

Highcal
07-28-2014, 04:16 PM
I only had the lid off for about 20 seconds.

scrub puller
07-28-2014, 05:17 PM
Yair . . . Highcal


Scrub, I have no risers, I have three 3/4" nipples and one 3/4" ball valve, I would think its getting plenty air intake, no ?


Dunno mate. As I said I have built a few now and can never get them to work with just four 3/4" holes . . . must be something to do with our Southern Hemisphere air. (big grin)

I look at pictures of UDS's such as yours that obviously work fine (even with ball valves and plumbing) but I have had to standardise on six 1"1/4 intakes (in pairs) controlled by a simple rotating flaps.

I do cook hot and fast though and like to have them cranking.

As has been mentioned a couple of dozen legs of chix could suck up a lot of heat.

Cheers.

Carbon
07-28-2014, 06:24 PM
I've never experienced this temp spike on my UDS. And I open the lid often to peek.
Goes to show every UDS is different.