Pellet Fan
Pit Talk -- Comments and Questions Regarding These Pellet Pits => GMG => Topic started by: 4given on July 01, 2020, 10:53:39 AM
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Howdy!
I have a GMG DB that I have had for about 7 years now. It has been a great rig and is still running strong. The only problem I have been having is I keep burning up the combustion fan housing gasket. I can always tell because I start getting soot on my food.
It is doing it again but this time I am thinking of forgoing the new gasket and just using Permatex 81878 Ultra Copper Maximum Temperature RTV Silicone Gasket Maker.
Anybody else do this and how did it work out?
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I believe you have the answer using Ultra Copper. Permatex isn't the sole supplier anymore making it easier to find. I have used it on several kamado gaskets and found it to preform well over the years..
What you will find is that it doesn't store well once opened. The silicone hardens in the tube in a few months.
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Have you ever tried car gasket material?
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Have you ever tried car gasket material?
Looks like it is a high temp gasket material:
(https://images-na.ssl-images-amazon.com/images/I/81I%2BjON27mL._AC_SL1500_.jpg]https://images-na.ssl-images-amazon.com/images/I/81I%2BjON27mL._AC_SL1500_.jpg)
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Good product. Used it on my Davy Crocket and LG 700 to seal some air leaks, and it worked great.
.......... :bbq:
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Howdy!
I have a GMG DB that I have had for about 7 years now. It has been a great rig and is still running strong. The only problem I have been having is I keep burning up the combustion fan gasket. I can always tell because I start getting soot on my food.
What makes the bad gasket get soot on your food?
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Howdy!
I have a GMG DB that I have had for about 7 years now. It has been a great rig and is still running strong. The only problem I have been having is I keep burning up the combustion fan gasket. I can always tell because I start getting soot on my food.
What makes the bad gasket get soot on your food?
I was wondering the same. Makes me think that the fan is going backwards?, but I guess you would see smoke coming out from the fan. ? No reason for there to be that much heat at the fan area. ??? Anyhow, I agree that any of the high temp "gasket" stuff would work fine. At the auto stores you can get *700 plus gray gasket material that is great and blends in well with most pits. But the red or copper stuff works as well.
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I don't' own a GMG but have noticed on my buddy's that they use somewhat of a positive airflow to work properly. Even makes a difference if if hopper lid is open. My choice would be a new gasket with a bead of Permatex and be done with it.
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The reason for sooting is a change in air to fuel ratio. Same amount of fuel but less air as going into the burn pot . The air the combustion fan generates takes the path of least resistance being the gap between
the fan housing and the pit body that was sealed by the fan gasket... The gasket has has burnt away leaving a gap.
https://greenmountaingrills.com/products/new-parts/jim-bowie-new-parts/combustion-fan-gasket-db-jb/
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The reason for sooting is a change in air to fuel ratio. Same amount of fuel but less air as going into the burn pot . The air the combustion fan generates takes the path of least resistance being the gap between
the fan housing and the pit body that was sealed by the fan gasket... The gasket has has burnt away leaving a gap.
https://greenmountaingrills.com/products/new-parts/jim-bowie-new-parts/combustion-fan-gasket-db-jb/
can you get a flame out also?
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The reason for sooting is a change in air to fuel ratio. Same amount of fuel but less air as going into the burn pot . The air the combustion fan generates takes the path of least resistance being the gap between
the fan housing and the pit body that was sealed by the fan gasket... The gasket has has burnt away leaving a gap.
https://greenmountaingrills.com/products/new-parts/jim-bowie-new-parts/combustion-fan-gasket-db-jb/
can you get a flame out also?
I wouldn't think that the lower air delivery to the fire pot due to a gasket leak would be totally be responsible. It sure as heck is responsible for poor combustion and that with other factors could result in a flameout.
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The reason for sooting is a change in air to fuel ratio. Same amount of fuel but less air as going into the burn pot . The air the combustion fan generates takes the path of least resistance being the gap between
the fan housing and the pit body that was sealed by the fan gasket... The gasket has has burnt away leaving a gap.
https://greenmountaingrills.com/products/new-parts/jim-bowie-new-parts/combustion-fan-gasket-db-jb/
I understand how the poor seal around the gasket could allow air to be leaked out but how does the heat get drawn back all the way to the fan area? Is it because there is more air flow than the holes in the firepot can accept? i.e. creating a back pressure? Anyhow I am sure that using the gasket with high heat gasket material as a sealer will solve the problem. Good sleuthing John!
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The reason for sooting is a change in air to fuel ratio. Same amount of fuel but less air as going into the burn pot . The air the combustion fan generates takes the path of least resistance being the gap between
the fan housing and the pit body that was sealed by the fan gasket... The gasket has has burnt away leaving a gap.
https://greenmountaingrills.com/products/new-parts/jim-bowie-new-parts/combustion-fan-gasket-db-jb/
I understand how the poor seal around the gasket could allow air to be leaked out but how does the heat get drawn back all the way to the fan area? Is it because there is more air flow than the holes in the firepot can accept? i.e. creating a back pressure? Anyhow I am sure that using the gasket with high heat gasket material as a sealer will solve the problem. Good sleuthing John!
Conduction: Heat travels from hot to cold. The pit body is hot and the fan housing cooler.
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Maybe it's not a consideration, but will the Permatex "glue" the fan to the pit making it difficult to replace?
Perhaps you could put waxed paper on the pit then run the Permatex bead on the fan and bolt it in place. When the Permatex is set up (and "glued" to the fan), remove the fan and discard the waxed paper. That might leave an exact gasket on the fan.
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Maybe it's not a consideration, but will the Permatex "glue" the fan to the pit making it difficult to replace?
Perhaps you could put waxed paper on the pit then run the Permatex bead on the fan and bolt it in place. When the Permatex is set up (and "glued" to the fan), remove the fan and discard the waxed paper. That might leave an exact gasket on the fan.
I tried that on my Blaz'n lid. It worked but was a little messy around the edges. Should not be visible problem with the fan. My advice: don't tighten the fan down flush when you make the gasket. Just a gentle snugging. That way when you remove the wax paper, you can then tighten it down a bit tighter. Be patient and wait at least 24 hrs before unbolting and removing the wax paper..Interesting how some fans used are induction type with a box frame and others (like Traeger and RT) are not enclosed.
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Maybe it's not a consideration, but will the Permatex "glue" the fan to the pit making it difficult to replace?
Perhaps you could put waxed paper on the pit then run the Permatex bead on the fan and bolt it in place. When the Permatex is set up (and "glued" to the fan), remove the fan and discard the waxed paper. That might leave an exact gasket on the fan.
The gasket goes between the fan housing and the pit body. The fan mounts to the fan housing so there is no worry there. A silicone seal/gasket is for the most part easily undone.. The bad part is removing the silicone material from the sealing surfaces .
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Soot caused by a burnt out combustion fan gasket was discussed at length on the "old other" pellet site years ago. I cant remember "why" it causes soot, I just remember that id "does". I seem to remember that GMG recommended replacing the gasket for soot as well.
When mine started have the same issue I checked the gasket and sure enough it was burnt out, and I mean burnt to a black crisp. Very little of it was left. I replaced the gasket using the red hi temp silicone and that solved the problem for a few more years. Now I am getting soot again so I figure it is probably the same thing. This time I want to leave out the gasket and just use the copper Hi temp gasket maker. I think it will last longer this way.
I think the fan gasket gets damaged when you run the grill at 450 - 500.
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Soot caused by a burnt out combustion fan gasket was discussed at length on the "old other" pellet site years ago. I cant remember "why" it causes soot, I just remember that id "does". I seem to remember that GMG recommended replacing the gasket for soot as well.
When mine started have the same issue I checked the gasket and sure enough it was burnt out, and I mean burnt to a black crisp. Very little of it was left. I replaced the gasket using the red hi temp silicone and that solved the problem for a few more years. Now I am getting soot again so I figure it is probably the same thing. This time I want to leave out the gasket and just use the copper Hi temp gasket maker. I think it will last longer this way.
I think the fan gasket gets damaged when you run the grill at 450 - 500.
I've had my DB for 5 years now and had the wiring get burned. That was due to a faulty controller that said 800 on it. GMG sent me a new harness but I have still used the same one. I don't do a lot of cooks at 450-500 so I was wondering how many cooks have you done at those temps? Thanks for you info! Some things to remember.
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I used to do quite a few chickens at 450 to get crispy skin. It was greasy and messy but it worked well. after the gasket burnt out and I replaced it, I decided not to do any more cooks over 350F. Now I find out that my wife has been cooking at 400 plus with it. I guess she didn't get the memo. :) ;)
I figure that might be why I am having problems again.
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Maybe it's not a consideration, but will the Permatex "glue" the fan to the pit making it difficult to replace?
Perhaps you could put waxed paper on the pit then run the Permatex bead on the fan and bolt it in place. When the Permatex is set up (and "glued" to the fan), remove the fan and discard the waxed paper. That might leave an exact gasket on the fan.
Another possibility would be to wipe down the mating surface with silicone oil prior to putting the fan and Permatex on. That 'should' allow for easy removal, and also the need to remove the wax paper as silicone oil should be good to around 475 degrees.
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UPDATE:
I took the combustion fan housing off this weekend and sure enough, the gasket was burnt and in pieces. If I wasn't clear before, this is the gasket were the fan housing connects to the bottom of the grill. (See picture below) It's a two person job. You need one person on top to hold a wrench on the bolt head and another person underneath to ratchet off the nuts. As you can see in the attached picture, there are 6 bolts to remove.
(https://cdn.shopify.com/s/files/1/1723/1387/products/IMG_20200626_135247_small.jpg?v=1594750494)
I removed the old gasket and sealer, l cleaned and wire brushed the surfaces and reassembled using the Permatex Ultra Copper only. Let it cure for 24 hours then cooked a spatchcock chicken to test it out.
Worked great! NO MORE SOOT!!! :cool:
I't is my hope that this is a permanent fix.
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That (Permatex Copper) should be the end of your gasket burning problem.. Just makes me wonder; why wouldn't GMG either go with a high temp silicone seal or a more heat resistant gasket? This seems to
be an on going problem that if corrected would rate their pits one increment higher on the reliability scale. Part of the answer is "up front " cost. The pay-back could far offset the minuscule cost in future pit
sales.
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The new GMG Prime and Prime plus grills don't have a combustion fan under the firebox. They now have one fan under the hopper that pushes air from the hopper to the firebox in a chamber similar to furnace duct work. Still have airflow to firebox like before, just one fan instead of two. One under the hopper and one under the firebox.
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The new GMG Prime and Prime plus grills don't have a combustion fan under the firebox. They now have one fan under the hopper that pushes air from the hopper to the firebox in a chamber similar to furnace duct work. Still have airflow to firebox like before, just one fan instead of two. One under the hopper and one under the firebox.
Interesting.
I've decided not to upgrade to Prime. I'm just going to keep refreshing mine every year or two and replace parts as needed. Thats one of the nice things about GMG. You can buy and replace every part if need be.
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The new GMG Prime and Prime plus grills don't have a combustion fan under the firebox. They now have one fan under the hopper that pushes air from the hopper to the firebox in a chamber similar to furnace duct work. Still have airflow to firebox like before, just one fan instead of two. One under the hopper and one under the firebox.
Do the Choice Grills have the just one one fan under the hopper too?