Hot stack

[red/one]

Hey guys, another stack question. 2x6 arch. I have minimal distance behind my stack and a low ceiling. My stack is 8" single wall stainless from SLM from the base up. To give you an idea of how low my ceiling is, the first section after the base sticks through the roof 6". Behind my evaporator is almost zero clearance to the wall and the stack is about 10" from framing. I did a bump out the width of the evaporator. Needless to say the back wall framing still gets extremely hot from the stack. The back wall is wood studs and metal roofing for the sheeting. I have already insulated the roof penetration with ceramic and flashing which is that first section above the base stack. I tried to insulate the base stack and reached out to SLM because it made the stack red hot and they told me to never insulate the base stack. So, can I get away with placing galvanized roofing behind the evaporator and stack to protect the wall? Should I scramble and add on to my sap house? Would hardi backer work? Sorry for rambling... Thanks in advance!

[O3C]

I have a little higher ceiling, must be 8 feet from the floor , and also 2x6 evaporator. I was nervous about burning down the sugar house so I wrapped that pipe with 1' ceramic and put 3 long heavy zip ties around the insulation. Figured if they fell off that would be my first sign from God that we had a problem! It would look better and probably do a better job if we wrapped that with some kind of flashing, but the zip ties have never fallen off. Ron

[Woody77]

I would use the metal just install it with an air gap between the steel and wall. This can be done early with a couple of cheep nuts placed over the screw or nail in between the steel and wall. 1" air gap is code on most H.V.A.C applications. Good luck red/one.

[tgormley358]

Wouldn’t a cement backer board be less conductive than the sheet metal? That’s what I used between the base stack and framing, with 1” spacers behind the board. I ended up with more space to the wall than I even needed about 10-12” and would take some of it back if I could as my shack is only 12’ on that dimension and my evaporator is 6’ long, leaving me only 5’ at the open end.

Tom

[red/one]

Thanks for the quick replies! Jim from Smokey Lake replied back to me also (email) and said cement board. I.m leaning towards that with the air gap. Just need to find some 1" spacers.

[Sugarmaker]

FYI I had very hot base stack issues at one time I added another layer of stainless around the base stack with some air gap. Then I even dirilled holes in the back of that covering and added another layer of stainless with another 1 inch air gap. With stack temps around 400 F now you can put your hand on the third layer. I personally believe that all the base and smoke stacks should be at least double wall with air circulation as a sugarhouse safety issue! I am not sure why manufactureres are not on board with this yet. Seems like a no brainer to me. Yes maybe more expensive, but look at the cost of the sugarhouse, contents, and safety during boiling. It well out weighs the cost of the materials.
Regards,
Chris

[SmellsLikeSyrupNH]

Cement board is what I use, it works great. I have maybe 12" from my stack to the wall. Home Depot or Lowes sell it in the flooring section. I took 2 pieces and attached them to the wall then I put sheet metal over them so that it looks nice. Works great!

[buckeye gold]

Red/one

couplers make great spacers. Or just cut a piece of 1/2 PVC in the desired lengths. If you want metal then use conduit connectors. I used pvc on cement board where my stack goes through the rafters. I put a digital thermometer up there and it stays between 115 -140 ( wood combustion is around 350). I'd use the hardy board as it is more solid than fiber bonded cement board. I also wrapped the top half of my stack with ceramic blanket. I think if you put up the hardy board and space it, you'll be fine, if you want another option put up arch board, but it cost more and isn't as durable.

[red/one]

I just remembered that I have 2 aluminum deck spindles left over from a project that I can cut into 1" pieces. I'll head over to the local supply store and get some hardi backer and make it safe for the weekend run. Good ideas guys!

[red/one]

Ok guys, I put the hardi backer up behind my arch with the air gap. I also removed the insulation from the base stack. One question, will the first piece of stack above the base be in jeapordy if it is insulated? It is single wall stainless steel with ceramic and flashing. I need the insulation as it goes through the roof and has framing around it.

[jrm]

So a question on the hardiboard, or cement board in general. While I boil outside, the last few years I've had half-sheets of plywood surrounding my evaporator as a windbreak. My first year, before the windbreak, my stack tipped on me, with a fire going. Fortunately, I was able to rectify the situation without a "real" fire. Learned about guy wires and moved on.

Seeing this thread, as well as comments about cement board in a few others, I thought it would be a good thing to add and have picked some up. I cut one of my pieces to the size I needed and was getting ready to pull the label off, mostly so it wouldn't go flying on a windy day. Read the warning, which is about the silica content and not breathing it in, etc.

Any worries, or anything I should do, to protect from the potential of silica dust blowing into my pans? I'm thinking in particular since I have cut edges.

Thanks.

[red/one]

jrm, if you can, put the cut edges below the pan level. If not, after you cut it use a gloved hand and wipe off any frays. I have a cut edge and I am confident it will be ok. Maybe there is some kind of self adhesive tape that will cover the joints/edge and take the heat from the arch.

[BCPP]

Jim, I think the only significant danger from silica dust is while it ou are cutting it. Once cut and lightly sanded and wiped off I doubt any dust will come off.