Bradley's Got a New Home

[classicrockgriller]

I think we may be working on a problem that hasn't happened yet. ;D

[BuyLowSellHigh]

I thought it did happen ?    ???

Here be one simple test (unfortunately, the brisket is done and the opportune time has passed)

Open vent 170, close vent get 220.  Is it reproducible?  Test = open vent again -- does temp go back to 170 and stay there?  If so, then ventilation is likely the issue.  Drop a bit but come back up?  Then it was probably timing vs. what's going on with that brisket. 

BTW, we are talking about a brisket, yes?  So where are the pics and how was it?

[KyNola]

I removed all of my posts because I was too stupid to read Rainmaker's original post close enough to realize that indeed he did have a load in the smoker when his dilemma occurred.  Thanks to BLSH for pointing it out.

Rainmaker, listen to these guys.  They know of which they speak.

My apologies everyone.

[Rainmaker]

Sorry for the delay in replying to all of these posts.  We were enjoying the brisket - which really did turn out good.  Sorry no pics.  Thanks again to Pachanga for a great recipe. 
Having read the above posts, I think it is a case of the stack causing an extra draft through the cabinet. I did notice when preheating the cabinet that it was still only up to 185 after an hour or more of preheating.  The cabinet temp is controlled by the Auber.  Both the Auber and the gauge on the door read the same (or close).  There was a fair bit of moisture in the cabinet as I had replaced the Bradley bowl with a full size aluminum pan and filled it with water.  (Last time I did a brisket, the pan ran out of water during the night and I didn't want that to happen again.)

However, I have figured out how to use the vent so I can adjust the flow of air to get the temp I need.

Someone mentioned having a fire plan.  The OBS is right up against a large window.  If I open the window and push even moderately hard, the OBS and the piece of panelling you see in the picture will end up outside the house.  Fires not out, but at least the house won't go up.  (If I push hard enough, it might end up on the neighbours yard.)

I'll do some more experimenting tomorrow to see how much of a draft there is coming out of the exit vent

[Habanero Smoker]

Looking at how you attached the duct, you may be able to get rid of the tape and use 4 - 6 earth magnets that are about the diameter of a nickle or larger.

[GusRobin]

Just add a second element and you won't need to worry about temps anymore. Regardless of what the meat load is, mine gets to where it needs to be in a hurry and pretty much stays where it is supposed to be. :D

[Rainmaker]

I would love to have a second element.  Trouble is I am technically challenged, especially when it comes to working with electricity.

[RAF128]

I've been following this as his set up is similar to mine.   Only difference I see is his vent goes straight up and mine bends to the left then out.    Could it be that the vent tube is acting like a chiminey and drawing the heat out of the cabinet faster than the element can produce it.   Might be why he's getting higher temps when the vent is closed. 

[Rainmaker]

I'm going to shorten the length of the rise.  Since the window is quite high and comes down below the height of the OBS this will be relatively easy to do.  Although, I'm challenged with working with electricity, I don't mind trying to do carpenter or mechanical projects (harder to electrocute myself). Want to do some tests first.

[Rainmaker]

I conducted a test to measure the impact of the "venting" set up for my OBS.  It is located in a glass sunroom attached to the back of the house.  I first heated the cabinet for 30 minutes (controlled by the Auber) without the vent attached (vent full open) and measured the cabinet temp.  I then attached the vent as shown in the picture and repeated the test.  (I should add that I waited until the cabinet had returned to room temp.)  Outside wind was very calm.   No water in the drip bowl.   Results are below.

OBS Not Vented to Outside
         Start      + 30 mins   Change
Room temp          53 deg      52 deg      -1 deg

Cabinet Temp      53 deg      213 deg   +160 deg


OBS Vented  (As in Picture)
         Start      +30 mins   Change
Room temp          58 deg      65 deg      +7 deg

Cabinet Temp      58 deg      197 deg   +139 deg

These results indicate that the venting system I have hooked up have a negative impact on the heating ability of the OBS.  It seems to be some sort of "chimney effect" causing an increased draft through the cabinet that exhausts the hot air faster.  So, I am wondering if I shorten the "stack" by putting the exhaust hole in the window about the same height as the OBS, will the "chimney effect" be reduced?

Would appreciate any ideas before I make the change.

[Rainmaker]

the "start" and "+30 mins" and "change" line isn't lined up well on the above post it should be moved right a bit.

[BuyLowSellHigh]

The chimney varies as the square root of height, all other things being equal.  To double the draft or flow (measured as a volume per unit time) requires a 4X increase in chimney height.  So the simple answer to your question is yes, if you decrease the stack height the chimney effect and flow will be reduced.  But with a single data point there is no way to estimate how much of the temp difference you saw will be recovered for the change you plan.  You may get it all back or a just a fraction.  But it's moving in the right direction.

[Rainmaker]

Do you see any problem if the exit through the window is lower than the top of the Bradley?  It will increase the length of the hose a bit.