Modifications Complete PID, 750 Watt Element & Fan

rgardjr · November 21, 2005, 12:27:20 AM

I've been busy modding the smoker over the past week and I finally got everything put back together and working. I added a fan and another element to the smoker. I'm not very impressed with the fan mod thus far. I'm still seeing a 20+ degree temp difference between the bottom rack and the second rack from the top. The addition element preheat the smoker very quickly and I should be able to load it up and not have any problems maintaining temperature. I also bought a PID and installed a thermocouple in the smoker for automated temp controll. The PID works great at keeping the smoker around a desired temperature. I used the autotune feature and set the temp at 215. After the autotune cycle the temp stayed at 212 or 213 for a 12 hour test period. Not sure why it never actually gets above 213, but that's alot closer than I was able to get before. I took a few pictures and I'll answer all questions.

Inside of smoker New Fan, New Element and New Thermocouple

PID Enclosure

I haven't added it up yet, but I'm probably pretty close to $100 into all the mods. The PID controller is in a stand alone box that plugs into the smoker. I incorporated a switch on the second element so that the smoker can be returned to stock with a flip of the switch.

Oldman · November 21, 2005, 03:18:16 AM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">. I'm still seeing a 20+ degree temp difference between the bottom rack and the second rack from the top.<hr height="1" noshade id="quote"></blockquote id="quote">

Rick it looks like to me your blade is wrong side out. It has to be screw (set) side out. The prototype you saw was originally CCR not CR as the motor you are using now.

I'm only seeing 2 degrees at best from the top of the V pan to the top of the box.

EDIT I just ckeck your image against my original image (see below) and your blade does look like it is facing the wrong way. If it is it does not move any air.

If you added one to the outside make sure the set screw is facing the back of the box and not towards the motor... [:D]

One more thought.. now that I think of it I did have one fan blade that for whatever reason did not move any air to speak of at all.

BTW Nice job on your mods...

Olds

rgardjr · November 21, 2005, 04:07:39 AM

Raye-
I do have the fan mounted backwards!!! I will fix it tommorow and have another test to see how it performs!

Oldman · November 21, 2005, 04:14:09 AM

Phew... that makes me feel better. To test your float without any heat or smoke you can use baby powder. Just place some in a sock and then lightly tab the sock with a pencil--while holding the sock above the fan blade--a light amount will come out and you will get a good idea of the float. [^]

Olds

rgardjr · November 21, 2005, 07:49:34 AM

Looks like I have the outside cooling fand back wards too! That one's a little more work to fix.

KosherSmokin · November 21, 2005, 05:17:07 PM

Hey rgardjr, love your mods!

First of all, do you have the thermocouple screwed into the wall?
Do you ever find your temp readings spike? The bullet smoker (yeah, I need a Bradley) that I'm using my thermostat with has some heat conduction between the element and the walls, so the temp on the walls is never accurate. I have to use my thermocouple suspended in the air for most accurate results. What's your experience?

Secondly, have you figured out if your fan is producing the infamous backflow problem people were hinting about?
I would love to get my hands on one too!

Thanks for showing us your work.
Sam

Oldman · November 21, 2005, 08:01:35 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> Hey rgardjr...
Secondly, have you figured out if your fan is producing the infamous backflow problem people were hinting about?
<hr height="1" noshade id="quote"></blockquote id="quote"> Well I'm not rgardjr, but I believe from his E-mails he is using the same motor as I'm. If that is the case then there is no backflow through the generator. The unit is moving 35 CFM.

Olds

Oldman · November 21, 2005, 08:04:59 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Looks like I have the outside cooling fand back wards too! That one's a little more work to fix.<hr height="1" noshade id="quote"></blockquote id="quote"> I was afraid of that...

Olds

rgardjr · November 21, 2005, 09:29:31 PM

<blockquote id="quote">quote:<hr height="1" noshade id="quote"> Hey rgardjr, love your mods!

First of all, do you have the thermocouple screwed into the wall?
Do you ever find your temp readings spike? The bullet smoker (yeah, I need a Bradley) that I'm using my thermostat with has some heat conduction between the element and the walls, so the temp on the walls is never accurate. I have to use my thermocouple suspended in the air for most accurate results. What's your experience?<hr height="1" noshade id="quote"></blockquote id="quote">

Well the thermocouple I have goes through the wall of the smoker through a hollow bolt. I don't think that heat conduction is a problem because the readings are within a degree or two of the Maverick thermometer that sits within a 1/2" of the thermocouple. The tip of the thermocouple is actually suspended in the air-the thermocouple I'm using is just a stainless insulated 24 gauge wire with the end of the two wires welded together. The wire is not encapsulated in anything.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Secondly, have you figured out if your fan is producing the infamous backflow problem people were hinting about?
I would love to get my hands on one too!

Thanks for showing us your work.
Sam<hr height="1" noshade id="quote"></blockquote id="quote">

I don't think I have a backflow problem, but as you can see from earlier posts I don't have the fan blades on correctly. I did a little test last night, after I turned the fan inside the smoker around I was down to about a 12-14 degree difference between the bottom rack and second from top rack.

Oldman · November 22, 2005, 12:54:46 PM

Rick I wish I could be there to help you.

This posting is in reply to an E-mail to me from Rick.

Now I take it you have the set screw on the fan facing towards the door. Try testing this box without the extra element on. Remember this fan is only moving 35 cfm and that extra heating element very well could be out running that amount of cfm. Logic would dictate that this is in-part the problem. With your extra element it could very well be heating the air at the bottom of the box faster than the the fan can redistribute those extra calories of energy. I take it you are using the same motor I'm using. (?) You may find that with the extra extra calories of energy that you are going to have to go to a larger (Yuck) fan blade. If that is the case then you must consider that the larger fans are wider thus shaft length is going to become an issue. One thing you might want to do instead of a larger fan blade is to increase the pitch of the fan blades. That motor is 1/70 HP and that blade only requires 1/500 HP so increasing the load by increasing the pitch will not be a strain on the motor.

I did two 40 hour test with a temp range from 205 to 305 F and my box temp never varied more than 2 degrees bottom to top.

In your E-mail you talked about changing out the two blades. At $2.08 cost for the blade I would think that I would be easier on you to go get another fan blade rather than take your unit out to change the fans around.

Rather than using the baby powder to check your air flow do this. Get your box running with smoke generator. Open the door and wait one minute. The smoke from the generator should be directed back towards the fans as shown in this picture.

If your unit is doing this then you are getting all the flow the fan can give you. As you can see in this picture the smoke is floating towards the back. It is not flying towards the back. With the door closed the air flow would be from the element to the front of the box and then over the top of the V pan and then back to the fan. I believe this really helps to balance out the temp. Give this thought-line consideration when you read what I wrote below.

I studied the pictures you sent to me and something stands out. It is the amount of space between your new element and the bottom of the V pan. There is an air space of just about 2 1/2 inches between the original element and the bottom of the V pan. By looking at the picture below it looks like you almost split that amount into half of the distant. The V pan itself drops down about 1 1/2 inches. Even if your V pan is not touching that element I would just about bet a dollar to a dime that it is so close that it has in effect become in-part an extention of the element. This very well may be why you are getting the temp swings that you are. When testing the box temp it would just about be the same as placing your probe on the element itself.

Take a picture with your V pan in the Bradley and post it. I do believe there is a real chance that you will have to find another type of element, because if you drop this element down it will not fit with the water bowl.

Now I have never given any real thought to adding another element as where I live heat is not a problem. However, if I did have to add another element it would be the same type that Bradley is using and I would mount it across from the generator as low as I could and yet still be able to remove the bottom tray.

Do keep in mind that if all things are equal then your box should be like my box. The only factor I see that is different is the placement of that extra element. Oh ya, my element is glass and not the newer stainless steel one. I believe it cools faster than the stainless one.

If I was using a PID controller I would have my probe as close to the top of the V pan as possible. This certainly would help in controlling the temp you want.

Yes it is possible that by placing the probe close to the elements that the top of the box may in-effect be cooler. If your probe is 1/2 way up the box then without a doubt given where your new probe is at the bottom of the box has got to be hotter.

Sorry that I could not be of more help.

Olds

Oldman · November 22, 2005, 01:36:38 PM

Crap,

I just remember I did increase the pitch on my inside fan blade. I did this as the prototype I made was not turning as fast that the current motor.

However, even with the increase pitch, now that I have thought this over more, I don't think you can fix this problem as long as you are using that type of addon element. I believe you have got to have more air space between it and the V pan. Also you might just want to do a control test by not running the fan. See what your temp swings are like then. Just make sure that your probe is in the same place when doing both test.

Olds

rgardjr · November 22, 2005, 07:05:24 PM

Well it's getting alot better. Last night I completely opened up the top vent and I was only seeing a 5-6 degree variation. I'll increase the fan pitch today and see if I can lower it a little more. Even with the vent completely open the PID was able to maintain the temp within 1-2 degrees with an outside temperature in the 30s. I have to say thanks again Olds for all your help with the fan addition.
Rick

ChefBill · February 08, 2006, 01:06:05 PM

Oldman,
You and I were discussing the fan subject back in the middle of last year and then I got caught up in the "Katrina Flood" and lost my Bradley. Now I'm back in business. I would like to know what fan motor you decided on and what fan blade you came up with. Where did you get it?[?]

rgardjr,
What motor and fan did you decide on?[?]

Has it been considered putting the fan at the right side UNDER or OVER "V" pan and pulling smoke toward it?[?]

ChefBill
If you can eat it, you can smoke it.