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size of heating element

post #1 of 9
Thread Starter 

Ok, so I am starting to get parts togeather to start my freeze build, but how do you figure out what size of an element you need?

 

I picked up a 1000 watt hot plate for 15 bucks so I am hoping this is going to be good enough for a 13 cuft upright freezer.

 

anyone tried 1000 watts on something this size?  I am going to be smoking at 225 or less so I don't need to be able to get up to 300 or anything like that.

 

Steve

post #2 of 9

There are a lot of Heat BTU calculators on the net, google and find one, then find a watt to btu calculator.  Then double what the calc says for btus. You will be about right. 

post #3 of 9
Thread Starter 

Ok, so my PID, Probe, SSR and Heat sink came today, so now I can start getting bussy with the build.  I have a 1000 watt hot plate I was going to take the element out of, but I am wondering.. I have about 20 CU^FT of space to heat so should I be getting a bigger element?

 

Steve

post #4 of 9

How's the build coming??  About to order my PID, probe and SSR soon to get started on my build

post #5 of 9
Thread Starter 
Quote:
Originally Posted by sparky30_06 View Post

How's the build coming??  About to order my PID, probe and SSR soon to get started on my build



slowly haha, been working some long hours but I am off two weeks over christmas so I hope to get most of it done then.

 

Steve

post #6 of 9

 

 

I'm not too sure you will be satisfied with a 1000W heater, I think the new MES units are around 8 cu ft and they use a 1200w heater and you have about 60% more volume than they do.

 

Another thing to consider, and I'm by no means an expert on PIDs, but from what I understand from the directions I received with mine and how it functions, is the amount of time you program for the unit to heat up is not continuous, lets say I program the PID to heat from ambient (80°) to 120° in 15 minutes, the PID does not turn on the element and continue to heat until 120° is reached, ...let's say it reaches 120° in 10 minutes and then holds at 120° for 5 minutes, but rather it divides the difference in temp by the time and heats in short increments, I have found that when my GOSM is full and the set temp was not reached in the time I set, the PID holds at that step and does not advance, it does not continue to heat the element. 

 

What could happen with your 1000W element is you will have to set the time for a long period before the target temp is reached.

 

What I think is the answer when using a PID controller to heat a smoker is to use a high wattage heater 1500W-2000W range, that way when the PID is heating the element is at max and then the target time could be shorter.

 

Like I said I'm not an expert, I sure wish someone here that is would speak up and help us out and correct me if I'm wrong.

 

Gene

post #7 of 9
Quote:
Originally Posted by deltadude View Post

There are a lot of Heat BTU calculators on the net, google and find one, then find a watt to btu calculator.  Then double what the calc says for btus. You will be about right. 



Im confused...   "double what the calc says for BTU's"  really? 

 

I found this calculator on the net and it calculates BTU's and watts. 

http://www.heatershop.com/btu_calculator.htm 

 

I plugged in my measurements and it said I needed 4500 BTU's and 1380 watts.  I should double this??

 

 

 

post #8 of 9
Thread Starter 



 

Quote:
Originally Posted by JustPassingThru View Post

 

 

I'm not too sure you will be satisfied with a 1000W heater, I think the new MES units are around 8 cu ft and they use a 1200w heater and you have about 60% more volume than they do.

 

Another thing to consider, and I'm by no means an expert on PIDs, but from what I understand from the directions I received with mine and how it functions, is the amount of time you program for the unit to heat up is not continuous, lets say I program the PID to heat from ambient (80°) to 120° in 15 minutes, the PID does not turn on the element and continue to heat until 120° is reached, ...let's say it reaches 120° in 10 minutes and then holds at 120° for 5 minutes, but rather it divides the difference in temp by the time and heats in short increments, I have found that when my GOSM is full and the set temp was not reached in the time I set, the PID holds at that step and does not advance, it does not continue to heat the element. 

 

What could happen with your 1000W element is you will have to set the time for a long period before the target temp is reached.

 

What I think is the answer when using a PID controller to heat a smoker is to use a high wattage heater 1500W-2000W range, that way when the PID is heating the element is at max and then the target time could be shorter.

 

Like I said I'm not an expert, I sure wish someone here that is would speak up and help us out and correct me if I'm wrong.

 

Gene



this is good to hear, I was thinking along this way also, but PID usually varies the amount of input so the voltage going to the element, so they would run the element at say 1/2 voltage or lower when getting close to target temp or to maintain it.  the problem with this is we are using a on/off type relay so it can vary the voltage, so we end up with a full on or full off situation which makes it depend on "on time" to control the amount of heat. 

 

I did get a 40 amp solid state relay so in theory I could put this on a 25 amp breaker and run two 1000 watt elements and not worry about short on off cycles. 

 

now even using a PID controller you can turn of one of the 3 parts of the "PID" or more.  the proportional part is what causes the effect you are talking about by turning that off you wont get the power dividing relating to target temp you are talking about.  by turning of all the parts of the PID you are just left with a super accurate temp control that will be full on/off and regulate temp with in a couple degrees.  ideally we would want to use a variable voltage relay to take advantage of the full capability of the PID but those are a little to expensive for this boy.

 

Steve

post #9 of 9
This Thread was from a while back...... What did you determine? What type of element did you finally decide on and how did it work?

Thanks.... Getting ready to head down the same path.
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