Help Explain This Draft Setup. KAT - RF

mcyork28

mcyork28

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I have a couple cooks on a new to me Kat 24x60 RF. I am still working through this so hopefully it makes sense. Chances are it's just user error.

I'm getting about a 50 degree temp difference between the two tel-trus. The hotter side being closest to the fire box.

The first cook I did was a chicken on the fire box side of the cooker that turned out gray. I chalked that up to poor fire management as i was busy with other things and not really paying attention. My second cook was today and was broken into two different sessions as i am trying to learn this smoker.

The first session was one chicken quarter which had a very faint hint of gray on the skin. The second cook was four chicken quarters on the left side and they were really gray. I did add some wood right when I add the second batch of chicken but overall it seemed to running relatively clean.

I'm not an expert but the exhaust setup seems like it would restrict airflow to me. The smoker has a big fat six inch exhaust pipe but its choaked down on the inside of the cook chamber.

It may be that I just need to figure this cooker out. I'm not the most experiance offset user. Please take a look at the pic of the exhaust. Does that make sense?
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Well Im not an expert in smoker design but I can do simple math and it seems like the surface area of that vent is much less than a circle 6" in diameter. Maybe a way to increase velocity?
 
Call the guy from Kat BBQ Smokers. He is a really nice guy. I spoke to him about his smokers when I was in the research phase of getting a new smoker. (I ended up going with a local guy...JH Smokers...just to save on shipping costs.) I think his name is Ken or Kent, I can't really remember. But super helpful and a really nice guy. Visit his website for his phone number. I'm sure he'll answer any questions and help you work through your learning curve on your new KAT smoker.
 
Do you have or can you get pics of the exhaust opening from some different angles? From this pic it looks like there's just a solid plate of steel welded over the entire opening. Their site doesn't have any good pics of the inside of the cooking chamber either.

Also, are there tuning plates in the bottom? I know some RF's have plates that you can slide around to adjust the heat and get more even temps.
 
OK, is that pic showing the exhaust stack and how it comes into the smoking chamber? If so that's shocking and it would explain why you're having such frustrating drafting / airflow issues. I'd call them immediately and have that picture ready to send them...I can't imagine how that's their design as I've always heard strictly positive things about KAT Smokers.

Good luck and I hope you get it sorted out quickly...no way should they restrict airflow with a welded on cover to the smoke stack.
 
How deep is the opening? It's hard to tell based on the angle the picture is at but it looks like an inch at most?
 
I would like to say again that this might be user error. I'm simply trying to figure this pit out.

The pictures aren't the greatest because the pit is in my garage at the moment and the lighting isn't the best.

There is a V shaped channel that runs the width of the pit. There is another V shaped channel over the exhaust pipe. Hopefully the additional pics shows the setup a little better.

Maybe its supposed to somehow create more suction?
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I agree that piece of steel covering the exhaust is an issue. Personally, i'd cut it out and run it!!
 
Just call KAT and tell them about the issues you're having, and then ask them about those "v" shaped covers over the exhaust. I just can't see anyway in which those are actually helping the airflow, though I am often wrong. haha

Good luck.
 
If your stack is 6" diameter, that's about 28sqin surface area cross section. Eyeballing that vent on the cook chamber, it looks maybe 1.75" x 8" or so, which would be 14" or half the opening area that the stack is. Seems odd from a non-pit builder's point of view, but figure it was done that way for a reason.
 
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That's a down draft design, idea being it forces hot gas to drop lower on the exit side for better temperature balance.

It does appear to be restrictive for a 60" pit with 6" exhaust, best to consult builder before condemning or modifying it some of the best home built pits I've cooked on had a similar design and a stainless steel drywallers mud pan filled with water tight to the firebox side made for impressive temperature balance side to side and top to bottom.
 
I'm definitely not condemning anything. As I said, really just trying to figure the pit out.

InThePitBBQ - I was actually going to experiment with a water pan on the RF plate but was planning on running it opposite the fire box end. I'm curious about your suggestion to run it close to the fire box. Seems like the moisture would simply run out the stack.
 
mcyork28 said:
I'm definitely not condemning anything. As I said, really just trying to figure the pit out.

InThePitBBQ - I was actually going to experiment with a water pan on the RF plate but was planning on running it opposite the fire box end. I'm curious about your suggestion to run it close to the fire box. Seems like the moisture would simply run out the stack.
Click to expand...

I've been fooling with wood fired pits for a long time, built a few and bought a bunch every one of them outside of my Shirley's benefited from some tweaking.

By keeping the water just above the fire it keeps the water temperature higher, in all the Lang's I cooked with for years I extended the exhaust down into the pit and ran that water pan right in the corner closest to the fire and it made a world of difference.

Never had as much success running the water pan on the side opposite the fire no matter if it was a reverse flow or not but that extra humidity really made a difference when we placed remote probes all over the pit and recorded temps over the duration of a cook.

Be interesting to see what the builder has to say and spend some more time with it.
 
mcyork28 said:
I would like to say again that this might be user error. I'm simply trying to figure this pit out.

The pictures aren't the greatest because the pit is in my garage at the moment and the lighting isn't the best.

There is a V shaped channel that runs the width of the pit. There is another V shaped channel over the exhaust pipe. Hopefully the additional pics shows the setup a little better.

Maybe its supposed to somehow create more suction?
34d3961fb749bfd903dabcb40fab49b3.jpg
2b12833f0f18d903588785b7f4f5cb69.jpg
68220b77ab486684e410b1c91e22a63b.jpg


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Click to expand...

The other issue, as you can see by the two inch tape measure pic is that below the rack rail (thus the metal under the tape measure) has a 24” piece of metal welded in, blocking airflow from below the racks. The only way air can go in is across the top of the rack, down a little channel and up that small opening. I’ve seen downdrafts in pellet grills but they don’t have airflow under the grate blocked off.
 
You say it's new to you. I wonder if some genius that owned it before modified it. That's the only way that makes any sense to me. I'm no pit designer by any stretch. The math doesn't work out a 6 inch pipe would have 28.27 square inch opening. That would have 12 to 18 square inches max with that cover depending on how wide it is. (I'm guessing that plate is 6 to 8 inches wide?) If you wanted to bring the exhaust down so it's a grate level then fine. I've seen designs that do it like Pitmaker on their tradition flows with the "Vortex Exhaust", but if anything the opening into the cook chamber is way bigger than the exhaust exit.
 
I need to make a correction. - just measured the stack and it's only 5.5 inches. Not a big difference but I wanted to poi t it out.

I have a fire going in it now. Interesting thing happened. I out a putty knife under the door closest to the fire box for a while and it was running completely clear smoke. When I removed it, the temp dropped like 20 degrees and the quality of the smoke deteriorated. I wouldn't call it bad smoke but it definitly changed.

I want to say again that I am not bashing this smoker or its design. I'm simply trying to figure it out. I feel like I came off at pointing the finger at a quality builder when that wasn't my intent. I have spoken with him in the past and he has always been very helpful and responsive.

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Before you dig too deep - 1 question that I would ask....

Did you check both thermometers to ensure they were accurate?
 
SoCalWJS said:
Before you dig too deep - 1 question that I would ask....



Did you check both thermometers to ensure they were accurate?
Click to expand...
Good question,

I have a thermoworks smoke in there now and the two tel-trus are brand new. I tested them before I installed them and they were pretty close to eachother.

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Interesting... I have the smaller version (KAT 48x20) and don't seem to have that issue and from what I remember the design is the same (I'm traveling right now so cannot measure).

This might be a dumb question but assuming you are running wide open on both intake and exhaust? That is the way I always run and it works great... If I want the firebox side to heat up (as it sometimes runs cooler), I'll close exhaust about 30% and wait about 20 mins for heat to even out left to right.

I also cut my splits fairly small and warm them on top of the firebox for quick ignition and combustion.

Like others have said, call Ken and see what he has to say about it. Good guy...
 
The easiest thing IMHO is to call the builder. They'll be able to tell you if it came that way or if someone added it after the fact. They can also likely tell you the best way to run the pit. They likely did a lot of testing on it before putting it out on the market so they know how it runs best and probably experienced the same thing you are on some level. It's unlikely that a builder would add steel where there doesn't need to be unless there's a good reason for it.
 
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