Paragon Kiln

Just a note on why two SSRs.

When you are using USA 220 voltage there are two hot lines. One SSR would indeed stop the current flow, but it won't de-energize the coils. Even though the coils would stop glowing, and the door interlock was open, anyone who touched the coils with a knife or tongs taking a blade out would be shocked ... or electrocuted.
Two SSRs disconnects the power from both ends of the coils. This is the only way a door interlock would be of any good on a USA 220 volt oven.

On the cost factor, I am with JT.
Yes, you can use the cheapest SSRs, TCs, kanthal, PID, etc. but you are building a piece of precision equipment. Just like in cooking - the better the quality of the ingredients, the better the quality of the dish.
You are unlikely to get an good quality 8 gauge type K TC for $10. Then you need TC wire, a TC connector block, etc. That is a lot more than $12.
I also would get a better PID than a $20-65 unit for a HT oven.
The coils are the engine of the oven, and the wire size and quality should be the best.
I would say a person with knowledge of HT ovens and good shop skills in metal work and welding could build a good unit for $500. A person who isn't as well skilled may not be able to build one at all.
 
So the doubled use of the SSRs makes sense now. I just put a rocker on the other hot, I hadn't thought to run the SSRs in parallel. I think I will do this. Thanks. One less thing I can screw up.

There are a bunch of insulated 3.2mm (8 AWG) wire diameter k-type TCs on ebay for under $10 I bought a couple and tested. Accurate to limits of my ability to test with a cone. Unless you are referring to the block that connects the extension wire to the TC wire (which was part of the TCs I bought), I connected the TC extension directly to the PID. I forgot to include the TC extension wire, which I think I used about 1 yard of, so call that $1.5.

I won't argue about PID quality. I bought one from Auber instruments, I think I paid $65, and while the control quality seems spot on, the interface is not my favorite. I looked for something wifi enabled or similar but didn't really find anything that looked like it had a better interface and wasn't proprietary (in other words, I could find replacement controllers from paragon etc, but couldn't find a good wiring diagram and wasn't sure if I was gonna be able to wire them/set them up with non-paragon systems. Do these controllers come with wiring diagrams and do they allow full user adjustment and auto PID calibration?

I used ~40' of 16AWG kanthal A1 for the resistance element. If I had used a larger gauge wire, I wouldn't have been able to maintain the recommended coil spacing to achieve my required resistance in the room I had. Not sure if guys are running 14 or 12 ga kanthal but as I remember, I would have needed about 75' of 14 ga and 120' of 12ga for a similar resistance, and both of those lengths could not be stretched by a minimum factor of 3 in the space allotted without going up to a coil OD in the 1" range. I didn't do this because I didn't want to mill out that much IFB for one and because many of the high dollar kilns I looked at weren't using those gauges or those coil diameters.

I agree that if you don't have any of the required tools or know how to use them that this would be a tough project.
 
From my research people who used the 16ga wire had it fail sooner then later and end up going with 14ga. My oven uses 12ga for its elements. Oh and I looked back at my build thread and 40 bricks cost me $227. Here is my build thread is you wanted to see how I built mine.
https://www.bladeforums.com/threads/heat-treat-oven-wip.1407817/
 
Haven't made it to the end, but that build looks awesome. I may upgrade to that TAP controller in the future. I was worried when I looked that All I found looked to be specific upgrade controllers for individual kiln models. I thought that perhaps they had settings hard set from the MFR. Thanks for the info, I will read through the rest this evening.

The WIFI feature is particularly intriguing.
 
JAM said:
Hey, can I be your friend? :) I could use an oven for around $300.
Click to expand...
I've made one oven recently, that was for me. I have made a number of forges recently. I would send any business on that front to one of the dudes on the forum here who sells their stuff. I don't.
 
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