Heat treat oven improvements.

Blankblank

Blankblank

Joined
Feb 16, 2022
Messages
615
I'm having some recurring issues with my diy heat treat oven. Its really one thing in particular. The ceramic terminal blocks that are connecting to the heating elements, are getting too hot, and the metal parts on them are deteriorating pretty rapidly.

I'm wondering what I can do about this. Get better terminal blocks? I've done just about everything I can to try to insulate the area they sit in. Have packed any holes for the elements to go through (and the thermocouple) very tight but this area seems to get pretty hot anyway.

What work arounds are there? Does anyone have recommendations for quality ceramic terminal blocks, high temperature electrical wire (probably 12 awg or so would be good)? Is there a way I can get these parts further from the heat, that is practical?


If pictures are needed, let me know I will take some.
 
I've had good luck with a stainless bolt and nut to tighten down on the element wire and protrude through the insulation where another set of nuts are used to attach the copper power wire.

on another I tack welded the heating element to a piece of stainless bar stock and drilled a hole in the other end to attach the power
 
Blankblank said:
I'm having some recurring issues with my diy heat treat oven. Its really one thing in particular. The ceramic terminal blocks that are connecting to the heating elements, are getting too hot, and the metal parts on them are deteriorating pretty rapidly.

I'm wondering what I can do about this. Get better terminal blocks? I've done just about everything I can to try to insulate the area they sit in. Have packed any holes for the elements to go through (and the thermocouple) very tight but this area seems to get pretty hot anyway.

What work arounds are there? Does anyone have recommendations for quality ceramic terminal blocks, high temperature electrical wire (probably 12 awg or so would be good)? Is there a way I can get these parts further from the heat, that is practical?


If pictures are needed, let me know I will take some.
Click to expand...
Did you twisted wire from elements on ends ? If you not do that elements get hot right to the ceramic terminal blocks
 
Backyard said:
I've had good luck with a stainless bolt and nut to tighten down on the element wire and protrude through the insulation where another set of nuts are used to attach the copper power wire.

on another I tack welded the heating element to a piece of stainless bar stock and drilled a hole in the other end to attach the power
Click to expand...
Could you link or post a picture to show an example? That sounds like a possible work around, if nothing else works.
 
Blankblank said:
I'm having some recurring issues with my diy heat treat oven. Its really one thing in particular. The ceramic terminal blocks that are connecting to the heating elements, are getting too hot, and the metal parts on them are deteriorating pretty rapidly.

I'm wondering what I can do about this. Get better terminal blocks? I've done just about everything I can to try to insulate the area they sit in. Have packed any holes for the elements to go through (and the thermocouple) very tight but this area seems to get pretty hot anyway.

What work arounds are there? Does anyone have recommendations for quality ceramic terminal blocks, high temperature electrical wire (probably 12 awg or so would be good)? Is there a way I can get these parts further from the heat, that is practical?


If pictures are needed, let me know I will take some.
Click to expand...
Pictures always help
 
https://imgur.com/a/GMastvi

It's just stuffed full of kaowool back there so you cant see a lot, but you can see the 4 terminal blocks, that connect to the 2 coils. The thermocouple is in the middle (I had to take off the base to the the aluminum flashing out to show inside.
 
Also this seems like as good a time to ask as any.

So I lines the top and bottom of the oven with kaowool to help reduce the inner dimensions a bit, does anyone know what putting refractory cement on the kaowool would do to the heat up time? Reduce it? Increase it? Make the temperature more, or less stable? Any effect?

Also a picture of the inside to show what I'm talking about.

https://imgur.com/a/2i1Vpjm
 
I would remove the wool and place a layer of firebrick on the floor if you feel the need to reduce the volume. I would leave the top alone.
 
I wonder if I could get a longer thermocouple, and cut a hole in a piece of fire brick, and put it in the back of the oven. To cut down on size a bit more. I already have a layer of kaowool back there to help insulate the back (inside the chamber) I wonder if that would be worth it.
 
So no recommendations on wire that can withstand at least 1000 degrees farenheit? Idk what kind of temps its hitting back there, but I have a feeling that could help.
 
One more thing. Has anyone ever played around with the idea of doing something to circulate air in a diy oven?

Obviously any kind of fan bringing air in from outside the chamber would just cause a ton of problems with heating times, among other things. But I'm thinking, if there could be a way to get the air inside the kiln to circulate a bit, it could help with the temperature consistency in a kiln (as far as I see it, even a store bought kiln could be improved if this was. Being done). Now how much it would help, and if it's even possible with these kind of temperatures without whatever is being used failing. Idk.
 
Blankblank said:
So no recommendations on wire that can withstand at least 1000 degrees farenheit? Idk what kind of temps its hitting back there, but I have a feeling that could help.
Click to expand...
I wired mine with 12-gauge high temperature wire from McMaster (part number 8209K19). This is only good to 840°F, but I don't think it is getting near that hot.
 
Hubert S. said:
I wired mine with 12-gauge high temperature wire from McMaster (part number 8209K19). This is only good to 840°F, but I don't think it is getting near that hot.
Click to expand...
Someone ended up giving me a good suggestion. I'll move the terminal blocks as far as I can from the firebrick body of the oven. When I do that, I'll likely replace all the wiring back therex with some of the stuff you recommend, and get some of the terminal blocks (I think they sell ones that are very high temperature rated at McMaster)

That and replace the kaowool with firebrick. Then... oh yeah, I want an even longer thermocouple to get closer to the center, and get a reading right near the blades.


I'm still curious about the air circulation thing.
 
A.McPherson said:
I think N Natlek was working on a furnace with a fan at one point.

Dunno if he ever finished.
Click to expand...
Would love to hear about it.


So update. I have a firebrick on the way to cut up and place on the bottom, some new terminal blocks, and more 12 awg high heat wire on the way.

I may have to remake the coils again (god I hope not) to get the pig tails long enough to get the terminal blocks placed further from the firebrick.


After this, my next plan is getting some 100-ht (or ht-100 I cant remember) to coat the entire inside of the kiln (well most of it). Then I'll buy a longer, and hopefully better quality thermocouple to get it closer to the are my blades are going to be. As of now, it's at the height the blades are, but its reading temperature near where the kiln is likely going to be the hottest, and I just want to get it closer to where the blades are actually sitting. .
 
Last edited:
Ken H> said:
You're wanting a fan to circulate 1500°F to 2,000°F air? Might be an expensive device.
Click to expand...
Garret TR30R turbine can withstand up to 1050 C / superalloy material known as Mar-M-247/ but that is not enough for stainless steel temperatures . I experimented a bit with it, at 3000 RPM the exhaust turbine has enough airflow for the oven.

efUmDNY.jpg
 
You must log in or register to reply here.
Back
Top