Wall Behind Grill HELP

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The GCS
Junior Burger
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2012/09/05 18:24:15 (permalink)

Wall Behind Grill HELP

Ok, so I've looked around and I saw glz.juanc had a really similar post but I was hoping to get some clear replies with this. Sorry if it's repetitive. I have a P30. The walls are set up with regular home insulation between the outer aluminum skin and a piece of 5/8" plywood. There is then FRP screwed to the plywood. I have drilled 4 holes in the back lip of the grill and used 2x4's as spacers. I then used lag bolts to anchor the grill to the wall. Well needless to say, I almost had a fire during a test run.
I'd post pics but it wont let me. Anyways, the 2x4's got so hot that they started smoldering and got red hot on the bottoms. They were not in direct contact with the flame from the burner. I ended up putting a big sheet of SS on the wall with duct heating/cooling insulation between it and the FRP, and replaced the 2x4's with aluminum square tubing. 
There is a 3" gap from the back of the grill to the wall. I am just paranoid as all get out that its getting too hot and not sure how to be sure. Hopefully, some of you can help me out. 
Thanks in advance!
 
#1

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    THE WILD DOG
    Double Chili Cheeseburger
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    Re:Wall Behind Grill HELP 2012/09/05 19:31:10 (permalink)
    all of that happened prior to you putting SS behind you grill ?  If so, that is why you have to have SS behind your grill & or fryers. FRP is fire resistant but will still heat up to a large degree.   I would contact your HD , they will steer you in the right direction for your county, but feel free to ask away here. You will get the best advice from the forums. Just remember, each county is different so the answers will be different
    #2
    edwmax
    Double Chili Cheeseburger
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    Re:Wall Behind Grill HELP 2012/09/05 20:17:38 (permalink)
    The GCS

      ... Anyways, the 2x4's got so hot that they started smoldering and got red hot on the bottoms. They were not in direct contact with the flame from the burner. I ended up putting a big sheet of SS on the wall with duct heating/cooling insulation between it and the FRP, and replaced the 2x4's with aluminum square tubing. 
    There is a 3" gap from the back of the grill to the wall. I am just paranoid as all get out that its getting too hot and not sure how to be sure. Hopefully, some of you can help me out. 
    Thanks in advance!


     
    There is no gap where the AL tubing is.  The tubing will conduct heat directly to the SS sheet; the SS sheet will conduct heat to the RFP & plywood.   ... You can still have fire inside the wall where you can't see it, until it burns through the  outer truck skin or the inside SS sheeting.
     
    Codes require this area to be constructed of non-flammable materials.  Also, a heat shield with a 1 inch air gap is required.
    #3
    The GCS
    Junior Burger
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    Re:Wall Behind Grill HELP 2012/09/05 20:37:31 (permalink)
    Thanks guys. Edwmax, thats my exact worry. The plywood can start burning without direct flame contact and I wouldn't know until it's too late. I do have some duct insulation between the SS and the frp. The SS is only screwed on with 8? screws so when it gets hot it warps a bit which gives a little bit of an 'air' gap. I think, to be certain, I'll just bite the bullet and cut away the frp and plywood from behind the grill and then put the SS back on to cover the cutout. Then there is no wood directly behind the grill to unknowingly catch on fire. What do you think? I'm going out for the first time Tuesday so I just need to get it done. I just want to be SURE that nothing is going to be susceptible to burning. My county has really lax codes. No fire codes or anything so its up to me. Thanks a TON for the response!
    #4
    The GCS
    Junior Burger
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    Re:Wall Behind Grill HELP 2012/09/05 20:41:02 (permalink)
    I have a digital thermometer and the aluminum spacers are only reading around 180. I don't know how accurate it is and when I point the thermometer behind the grill its above 250. I think the heat rising up from behind the grill is throwing off my reading because if I stick my arm under the grill, right by the burners and check the temp its in the high 100s. I'm just really paranoid that the plywood will start smoldering. ugh...building my truck myself has had plenty of headaches and hurdles...hopefully it pays off! 
    #5
    edwmax
    Double Chili Cheeseburger
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    Re:Wall Behind Grill HELP 2012/09/06 07:13:54 (permalink)
    Wood studs have been known to ignite from the constant contact of 180 deg hot water pipes.   So low temps could start a fire if heated long enough ...  
     
    The heat shield with 1 inch air gap works as a radiant heat barrier.  The air gap cools the sheet & face of the wall by circulating air.  The air gap is not closed off at the top and bottom of the wall. I think 6 inch opening is required (??) full width of the shield.  The warping of the sheeting you described will not function as an air gap.
     
    Next, look at how the hot air/gasses (grill exhaust ) exits the grill.  Most grills have some sort of chimney. Some don't.   But if there is a chimney (my thinking), extend it up to the bottom of the vent filters.    This would go a long ways to help keep the truck cooler.
     
    There are several threads where this area of the wall has been discussed & other members have used SS sheeting over plywood.   ... You are the first (to my recollection) to state he had a fire due to the use of wood behind high temp commercial cooking equipment.      ... My point has always been, why take a chance on losing $40k -$50k value/investment in building a rig when the answer is really simple.
    #6
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