Heating Element Limitations

Jason Wilder

Well-Known Member
I converted my kiln to a HT oven as shown in this thread.

It has done well so far at getting up to 1500 degrees but I asked more than it could give today. I was in the process of HT'ing my first stainless and the heating element broke at around 1700 degrees. Honestly, I figured it would since the heating element was from a 30+ year old kiln.

I purposefully designed the kiln to be like Paragon's KM14D so I could use new heating elements when my old one broke. I actually have 3 more old spare elements I could use and confidently reach 1500 degrees but I built this hoss for stainless so my question is this: Do you foresee any problems with replacing my old element with a new element from Tracy for the KM14D?

My controller, thermocouple, and insulation will all reach 2300 degrees, but I want to make sure there won't be any problems with this element.

Thanks,
Jason
 
Hello Jason,

Nice conversion!
the paragon 14d is listed with 1200 Watts so you will need at least that. I design my ovens with a power requirement of 0,8W per cm² of chamber surfacewith good success, this would make for a 1600W element with your oven size.

There must be something wrong with the listed specs of your linked element because at 240V and 9,25 Ohms it will make a Volt²/Ohm= Watt = 6050W element which is way too much!

After doing all this yourself ever considered making the element also? For a 1600W 240V element you will need 18,3m (without tails) of 1mm kanthal A1 wire to make a suitable element for your kiln.
With 110V you will need 12,6m (without tails) of 1.8mm kanthal wire to make a suitable 1600W element.
Buying the wire will also be cheaper tham buying premade elements.

As for your temperature fluctuating problem you can try adjusting the P(proportional) I(integral) and D(deviation) values in your PID. Up to a certain amount you are able to adjust but if the oven is grosly over or underpowered the PID is not able to compensate this.
PID controllers are used to maintain precise temperatures. PID is short for Proportional, Integral, Derivative--the three variables that control the temperature controller's behavior. In a kiln, a PID controller uses a thermometer to monitor the internal temperature of the kiln and triggers the kiln's heating elements based on its internal programming. Different kilns have different interfaces for their PID controllers, but the principle behind programming them is the same.


1
Set the initial "P" value to 10, the "I" value to 1 and the "D" value to 1. Set the kiln to a target temperature and observe it as it attempts to maintain that temperature.
2
Increase the "P" value to increase the kiln's responsiveness. The higher the "P" value, the more the kiln reacts to a difference between the current temperature and the target temperature. A very high "P" value causees the kiln to over-react and overshoot the target temperature. Tweak the "P" value until you've reached the point where the kiln only slightly overshoots the target temperature.
3
Increase the "I" value if the kiln takes too long to warm up to the target temperature from its initial temperature. The "I" value essentially boosts the power to the kilns heating unit. If the "I" value is too high, the kiln will continuously boost above and below the target point. Set the "I" value to a point where the kiln heats to your target point rapidly with minimal oscillation around the target value.
4
Increase the "D" value until the kiln no longer overshoots or undershoots the target temperature. The "D" value controls how much emphasis the kiln puts on predictions of target temperatures. This allows the kiln to shut off its heating element before the kiln hits the target temperature.
5
Adjust the "P," "I" and "D" values as necessary based on the kiln's responsiveness, warm-up speed and overshooting tendency.
 
Wow!

Thanks for the detailed explanation! I had no idea even what PID stood for and the rest is just icing. :)

I was just doing some number crunching and if he ran that same coil at 120 instead of 240V, it would give about 1556W - pretty close to on target. Could this be a 120V kiln?
 
It is a 120v kiln since there is only one element. If there were two elements, it would be 220v. Tracy has them listed as 220 but Paragon says they are 120. Tracy's site also says there are two elements, but Paragon's site says there is only one.

Thanks for the explanation and the advice. I will try to adjust it.
Jason
 
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