Fan Mod Help!!

mikecorn.1 · March 09, 2012, 07:23:44 AM

OK so I think I wasted close to $100 dollars in this fan :'(. It does move air around but not nearly enough to keep the temps even from top to bottom. I don't even have any racks in the smoker so there is nothing interfering with the air movement or lack there of ;D. Same results no matter where i put the probes. I checked the probes with boiling water and they are accurate :). I have a 25 degree difference :o >:(. Its in the garage so there is no wind and the temp outside is 71. The dual 500 mod is working fine with the PID. Hovering between 224-226. Set at 225F.
For those of you that are having great results, what do you think is going on with those of us who are not having the same luck ???. I am even willing to try the dual fan blades inside, back to back to see if it makes a difference. I read a thread on here were it was done. Said it pushes up to 25% more air. JZ is going to try it and hopefully post results.

Gonna post pics with my phone to show how it is pushing air. give me a sec, I'm on the laptop and gonna upload them from my phone. just in case some one reads this while I'm getting the pics. ;D

mikecorn.1 · March 09, 2012, 07:26:59 AM

Here you can see the fan off and the tissue straight down. The probe is to the left of center and actually hanging between the v tray and where the bottom tray would be. The fan is not blowing straight at it. The top probe is down the vent also and its hanging right about where the first tray would be. (not shown on this pic)

Here the fan is on and the tissue although hard to tell, its actually moving and the bottom edge is right at the edge of the v-tray

So here are the latest temps. I closed the vents on the v-tray towards the back. All but the one closest to the drain hole. Left the
Ones toward the front of the smoker open. Think read this from viper125 post.
(disregard the temp on the maverick food side it's 13 degrees off and sitting on the concrete. The oven probe reads perfect during water boil test.)
The ET732 is getting the RTV silicone treatment. ;D

Sent from my iPhone using Tapatalk

JZ · March 09, 2012, 08:13:33 AM

Same thing here. I didn't check temp variations inside the chamber with thermometers but the results were obvious on the meat.

I am going to stack the blades if there is room and will let you know what I find. But I don't think this will do the trick.

Sam3 · March 09, 2012, 08:43:18 AM

Mike, perhaps the higher temps that you are running it might be adding to the difference between top and bottom. Obviously that element is very hot and stays very hot.

Have you tried it at a low temp like 130 dgrees and checked to see what it was? I don't go over 170 with my OBS and have had no problems thus far.

Sam3 · March 09, 2012, 08:45:13 AM

I'm kinda thinking out loud, that's all.

TedEbear · March 09, 2012, 08:47:06 AM

What's the cfm rating on the fan blades you have? When I was shopping on the online Grainger site I remember they had a 2" blade with a 30cfm and a 2.5" with a 45cfm rating. If you're using the smaller blade you'd get a 50% airflow increase by going to the slightly larger size.

devo · March 09, 2012, 09:02:16 AM

I bought one of those little fans also and was very disappointed in the performance so i did a mod myself. Not that i recommend anyone going to the extreme I did but I can tell you I now have a very effective fan with good air flow and constant temps through out the smoker.

mikecorn.1 · March 09, 2012, 09:20:06 AM

Quote from: Sam3 on March 09, 2012, 08:43:18 AM
Mike, perhaps the higher temps that you are running it might be adding to the difference between top and bottom. Obviously that element is very hot and stays very hot.

Have you tried it at a low temp like 130 dgrees and checked to see what it was? I don't go over 170 with my OBS and have had no problems thus far.

Sam, now that i think about it, yes, when I was making sticks, the temps were even and or alot closer together when I was starting at 130. Even took a pic of it. When i got to 170 to finish, the temps were about 10 off from top to bottom. Ive been at this all morning trying different things. I was even going to buy an extra fan blade here locally for around $4 till I took my fan off and tried fitting both blades on the shaft inside just to see if they would fit. NOT >:(!! I put both blades on while the fan was off the smoker to see if I could tell the difference in flow. Cant really tell, thats not to say that once its inside mounted it will make a difference. JZ is also tinkering with his. Been PM'ing with him this morning. Hopefully he has better luck. :)

mikecorn.1 · March 09, 2012, 09:26:14 AM

Quote from: TedEbear on March 09, 2012, 08:47:06 AM
What's the cfm rating on the fan blades you have? When I was shopping on the online Grainger site I remember they had a 2" blade with a 30cfm and a 2.5" with a 45cfm rating. If you're using the smaller blade you'd get a 50% airflow increase by going to the slightly larger size.

Problem is that I dont thing the bigger blade will fit. I will most likely hit the v tray, its already a close fit mounted using the template that came with it. It sits right between the bottom most tray and v tray. Dont want to spend the money on another then it will not fit :) ;)
Thanks for the reply. :)

mikecorn.1 · March 09, 2012, 09:28:33 AM

Quote from: devo on March 09, 2012, 09:02:16 AM
I bought one of those little fans also and was very disappointed in the performance so i did a mod myself. Not that i recommend anyone going to the extreme I did but I can tell you I now have a very effective fan with good air flow and constant temps through out the smoker.

Where did you get that. I saw the thread where you commented on this saying that it wasnt pretty but it work. That doesnt look bad at all. LIL paint on there and BAM! coustom looking job. ;D

rigstar · March 09, 2012, 09:32:57 AM

Quote from: mikecorn.1 on March 09, 2012, 09:20:06 AM
Quote from: Sam3 on March 09, 2012, 08:43:18 AM
Mike, perhaps the higher temps that you are running it might be adding to the difference between top and bottom. Obviously that element is very hot and stays very hot.

Have you tried it at a low temp like 130 dgrees and checked to see what it was? I don't go over 170 with my OBS and have had no problems thus far.
Sam, now that i think about it, yes, when I was making sticks, the temps were even and or alot closer together when I was starting at 130. Even took a pic of it. When i got to 170 to finish, the temps were about 10 off from top to bottom. Ive been at this all morning trying different things. I was even going to buy an extra fan blade here locally for around $4 till I took my fan off and tried fitting both blades on the shaft inside just to see if they would fit. NOT >:(!! I put both blades on while the fan was off the smoker to see if I could tell the difference in flow. Cant really tell, thats not to say that once its inside mounted it will make a difference. JZ is also tinkering with his. Been PM'ing with him this morning. Hopefully he has better luck. :)

hey mc did you happen to look at the post by Docz, i believe he had to add a piece of
dowel and then siliconed the 2 fans together to make them fit on orginal shaft,
i am thinking that is because like you said the 2 won't fit on orginal shaft alone.
just another thought for you

Sam3 · March 09, 2012, 09:34:29 AM

Quote from: mikecorn.1 on March 09, 2012, 09:20:06 AM
Quote from: Sam3 on March 09, 2012, 08:43:18 AM
Mike, perhaps the higher temps that you are running it might be adding to the difference between top and bottom. Obviously that element is very hot and stays very hot.

Have you tried it at a low temp like 130 dgrees and checked to see what it was? I don't go over 170 with my OBS and have had no problems thus far.
Sam, now that i think about it, yes, when I was making sticks, the temps were even and or alot closer together when I was starting at 130. Even took a pic of it. When i got to 170 to finish, the temps were about 10 off from top to bottom. Ive been at this all morning trying different things. I was even going to buy an extra fan blade here locally for around $4 till I took my fan off and tried fitting both blades on the shaft inside just to see if they would fit. NOT >:(!! I put both blades on while the fan was off the smoker to see if I could tell the difference in flow. Cant really tell, thats not to say that once its inside mounted it will make a difference. JZ is also tinkering with his. Been PM'ing with him this morning. Hopefully he has better luck. :)

It also helped with the circulation of the smoke when I was making sticks and such. Everything had a uniform color on it.
Maybe because of the higher heat, you need something larger that will move more air like devo posted.

mikecorn.1 · March 09, 2012, 09:35:42 AM

Quote from: Sam3 on March 09, 2012, 09:34:29 AM
Quote from: mikecorn.1 on March 09, 2012, 09:20:06 AM
Quote from: Sam3 on March 09, 2012, 08:43:18 AM
Mike, perhaps the higher temps that you are running it might be adding to the difference between top and bottom. Obviously that element is very hot and stays very hot.

Have you tried it at a low temp like 130 dgrees and checked to see what it was? I don't go over 170 with my OBS and have had no problems thus far.
Sam, now that i think about it, yes, when I was making sticks, the temps were even and or alot closer together when I was starting at 130. Even took a pic of it. When i got to 170 to finish, the temps were about 10 off from top to bottom. Ive been at this all morning trying different things. I was even going to buy an extra fan blade here locally for around $4 till I took my fan off and tried fitting both blades on the shaft inside just to see if they would fit. NOT >:(!! I put both blades on while the fan was off the smoker to see if I could tell the difference in flow. Cant really tell, thats not to say that once its inside mounted it will make a difference. JZ is also tinkering with his. Been PM'ing with him this morning. Hopefully he has better luck. :)

It also helped with the circulation of the smoke when I was making sticks and such. Everything had a uniform color on it.
Maybe because of the higher heat, you need something larger that will move more air like devo posted.

TRUE. :) ;)

TedEbear · March 09, 2012, 09:36:53 AM

Quote from: mikecorn.1 on March 09, 2012, 09:26:14 AM
Problem is that I dont thing the bigger blade will fit. I will most likely hit the v tray, its already a close fit mounted using the template that came with it.

Well, it would only be 1/4" more at the top and bottom. I didn't think the tolerances were that tight.

I have a Dayton fan kit sitting in my basement that I bought from Grainger - I just haven't installed it yet. I think I bought the 2.5" blades for it. I noticed just now that they have a 3" blade with a 60cfm rating. I'll check the clearance when I get home this afternoon.

JZ · March 09, 2012, 09:39:33 AM

Ok I put the second blade on and fired it up. I had 3 temp gauges going 1 at the top, Auber PID in the middle and third one just above the vpan (about 3"). I set the PID to 200* and here are the results.

The middle and top readings stayed within 2 degrees of each other. The bottom one was different story. The temp difference between it and the other 2 was around 25* - 30* while the box was heating up and when it got to the set temp the difference started to drop. By the time the whole thing settled in for awhile the temp difference was around 16* - 18*. I did not check the temps at the back or front of the box and will go and move the probes to see if that makes a difference. NOTE THAT THIS IS WITHOUT A LOAD.

My conclusion is that the more heat that is required to maintain the set temp the more the variance will be. Once the set temp has been achieved it will take less energy to maintain it it and therefore the internal temps will be more even. Adding a large load of meat is going to mean more heat is required and as the temp differences will be greater because the elements will be on longer. Also as Sam3 pointed out the temp variations will be less at lower temps because less energy is required to maintain the lower temps.

I like Devos solution but not sure I want to take that step yet. Might just carry on with the current setup, since it is already installed.