Fridge Conversion Chimney Placement

dangerdan · Oct 4, 2008

I'm currently working on a fridge conversion. This is my third fridge smoker over the years and the last two had the chimney cut into the top. The last one really never even had a chimney, just a hole in the top of the fridge to let the smoke vent.

My question being, is there any benefit to running the chimney out of the back of the unit rather than the top? I've seen them both ways and would like a little input before cutting into the back of my current project fridge.

The small circle shown in this photo is from where the fridge light was installed. If I do cut an opening the bottom of the cutout would be at the bottom of the small hole. I'm considering a 5" to 6" cut-out as I'll be using a firebox from a chargiller for thie offset firebox. It would line up between the first and second shelves. The shelves are 8" apart.

richtee · Oct 5, 2008

Honestly Dan... I'd stick with the top and pop rivet or whatever a plate over the little hole. The heat/smoke will partially bypass the upper rack if you vent it below them, not to mention possibly creating a "stale smoke" pocket above the vent. I'd also center the stack in the top. A short length of pipe will help the "draw" of the smoker, in effect as a chimney does to a fireplace. Plus, you can damper it to keep out the rain/whatever when not in use, or tweak it for temp/smoke control.

dangerdan · Oct 5, 2008

Yeah, thats kind of what I thought too.. Just double guessing myself before putting it in.
Think twice cut once type a deal or something like that eh?
I also still have the old damper plug from my Chargriller. I can install it inside the fridge and use it for a secondary damper to control heat if I need to.

Hopefully this one will last longer than the other two. Fridges don't grow on trees anymore...

Thanks..

tn_bbq · Oct 5, 2008

Ever thought of doing a reverse flow smoker? Let smoke enter towards the top & exit from the bottom? It would require some extra channels and/or pipes, but that system works great with my Backwoods Smoker.

richtee · Oct 6, 2008

Hmm...really? What model? Seems like a strange setup, working against convection and all... is there a fan or something?

white cloud · Oct 6, 2008

retracted.

tn_bbq · Oct 6, 2008

Backwoods Smoker

Teams using Backwoods Smokers have won all the major competitions, Memphis in May, the American Royal, and the Jack Daniels Invitational.

http://www.backwoods-smoker.com/

They do offer (for a price) a convection fan option. Most folks don't go that route. I suspect if I did professional catering I would consider it.

Basics:

Double wall, vertical, water-pan, reverse-flow BBQ smoker.

The cooking chamber is separated from the firebox by the water pan. The heat/smoke flows up the sides of the cook chamber and actually enters the cook chamber from the top. The chimney inlet is in the lower back section of the cook chamber.

So, your cooking chamber is heated from all sides. In addition, the Backwood Smokers have insulated double walls that hold heat very well.

I'll post some pics.

richtee · Oct 6, 2008

Ahh OK. I did look them up. Interesting concept. I guess the heat/smoke has to go SOMEWHERE...even if it is against the normal flow of things.

tn_bbq · Oct 6, 2008

These things cook some serious BBQ.

That 1 inch gap at the top is the heat/smoke inlet. The heat/smoke runs up the entire side & rear of the chamber.

Closer view:

Chimney inlet (looks like Swiss cheese)

richtee · Oct 6, 2008

Well, cool. I got it now...thanks for the pix!

white cloud · Oct 6, 2008

I just seen two of those last weekend and have been considering a build myself. That is pretty cool how it works. Now it gives me more to consider. Thanks for the info

tn_bbq · Oct 6, 2008

The heat/smoke definitely goes SOMEWHERE in a Backwoods Smoker (BWS).

Folks modify their offsets in a similar fashion by lowering their chimney intakes with ducts/pipes, etc down to the cooking grate.

All I know is the BWS is a mighty fine smoker with a proven track record on all the competition BBQ cooking circuits. You'll probably find one at every competition event you go to.

Whether or not the refrigerator conversion would benefit from such a design is anybody's guess. I suspect I'd simply put the chimney intake at the top and go that route. You could always modify it at a later date with some pipe/ducting, but for starters I think I would go with the K.I.S.S. design (what's the fun in building something perfectly the very first time anyway?)

davenh · Oct 6, 2008

Nice looking fridge Dan! I was kinda wondering the same thing about where to put the stack on my build. Center top makes sense. Thanks

dangerdan · Oct 6, 2008

Nice design heating from the outside in and I like the idea of no direct heat in the smoke chamber. Unfortunatley I'd have to dig out all of my insulation and do alot more fabrication to seal the outer shell. Seems like I'm dumpin a ton of money into this conversion already.

I'm considering a pretty wild graphic design on this unit as long as the outer shell doesn't get too hot. I'm hoping to keep outer temps as cool as possible but hot enough in the smoke chamber to still get the versatility I'm looking for.

This unit will be expected to handle my cooler smokes, bacon, sausage, fish, etc.. If the outer shell doesn't get too hot, the hotter cooks roasts ribs etc. will be ok...

A lil testing will tell me what I need to know.

richtee · Oct 6, 2008

Honestly Dan... as long as you keep conduction of heat from the heat/smoke source to the OUTER shell at a min...you should be fine. But like we discussed... heat 'er up!

walking dude · Oct 6, 2008

i would maybe also add a fan of some sorts, so the smoke circulates the chamber some before leaving the chamber........if you have TOO much draw from the chimney, some of the meat may not get kissed by the smoke much...........

dangerdan · Oct 6, 2008

The firebox looks a little big to me.. I'm thinkin it's gonna get mighty hot in there..

Some masonry lath and chimney mortar should seal the openin g nicely.

My initial thoughts are to only cut the opening the size of the damper and give it a test run.

While laying out the firebox position I drilled a pilot hole in the center for an anticipated damper should I go this route. If I don't use the damper I think I'm going to need a pretty good sized baffle across the bottom.

I figure I can always cut the fire box cut out bigger if the smoker temps are too low. Once the hole is cut though, there's no uncutting it...

davenh · Oct 6, 2008

Dan...how are you mounting the firebox, directly to the outer skin with a collar to the inside? I'm just wondering about the heat transfer from the firebox to the outside skin.

I was thinking about mounting mine on some kind of spacers and bracket to keep it cooler.

Any chance you have a pic of your damper setup?

Edit: Guess I should refresh my page once and a while, your pics are already there..lol.

tn_bbq · Oct 6, 2008

Looks good.

I'd say the first half dozen (maybe more) times you fire that thing up will be a "test" run. That's sorta the deal (fun) when it comes to making your own smoker. Part of what makes this stuff a hobby.

I think adding that damper is a good idea. Might come in handy should your temps spike up on you.

You've probably already planned on this, but a tuning plate/damper/baffle that separates and shields your meat from the hot coals is probably a good idea too.

dangerdan · Oct 6, 2008

to seal the passage between the outer & inner shells I plan to put in some lathe and then mortar it with chimney mortar. If it doesn't hold up I'll consider another method but with a couple struts from the bottom corner of the fridge to the firebox it should prove to be sufficient.

The baffle is already being cut. I'm using a large diameter pipe (about 16") to cut a strip for the baffle. I stopped by the shop today and had asked about 26" but it was too flat.

Fridge Conversion Chimney Placement

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