Heat treat oven improvements.

Blankblank said:
So things are going well with the current integration of the oven. I'm about to improve the next weakest link. Which is the fuseholder. It is supposed to be rated for way above what I'm running it through, and its heating up way too much. Which means there are problems with resistance that shouldn't be happening. Its causing problems, and I've decided I need to go ahead and replace it.

If I'm going to do that I'm thinking I should probably just go ahead and use a breaker anyway. Now I have a couple choices on where I can go from here. Do you guys think I should use a gfci type breaker? It might make sense as far as dangerous electrocutions. Or rather just get whatever 20 amp breaker I find. (I'm thinking push button is the way to go).


Tl;dr my fuseholder sucks. I'm going to buy some kind of breaker for the kiln. What kind should I get?
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I bought a breaker switch from Auber Instruments when I got the PID controller and have had no issues with it.
 
I wanted to post this here, and see if I could get any opinions.

I've been noticing the live wire coming into the initial switch for my oven has been getting hot.

The main thing I can think of that could cause this, would be resistance. I've only really noticed this on the live side. The neutral doesn't have this issue, and nothing else in the box is heating except the ssrs which is normal as far as i know. The switches I bought are rated way higher than what I'm using, so I don't see why this should happen, unless they were just not well made.

I'm thinking it might be a good idea to just replace it with a higher quality switch, and go from there.
 
What do you mean by "hot"? Like melting the insulation, or getting uncomfortable to touch? Or just kinda warm? It's normal for high draw circuits to get warm.
 
A.McPherson said:
What do you mean by "hot"? Like melting the insulation, or getting uncomfortable to touch? Or just kinda warm? It's normal for high draw circuits to get warm.
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Its it's not hot enough to melt the insulation on the wire, but the plastic that the crimp on female connector that's connecting the wire to the switch gets hot enough to deform, and discolor a bit. If I keep a fan blowing on it, that's enough to stop that from happening. Its definitely uncomfortable to the touch, but not really hot enough to injure you or something.

The main thing is, that's the only place in the circuit that seems to get that hot, or any hotter than warm. Besides the ssrs, and those actually do don't really get hot as long as I have a fan blowing on the heat sinks (which also blows air on the connection I'm talking about too.
 
An oven runs continuously for hours. It is sort of normal for the wires to get warm. Hot is a different thing.

Most likely not a good connection at the switch. Cut the end off and re-connect with a properly crimped lug. You can even solder the lug after crimping.
The other thing might be too small gauge wire used for the power cord or tool long a power cord (is it plugged into an extension cord?).
 
Its definitely some kind of bad connection. I'll try crimping on a new one. I do use an extension chord. Its 6ft long. Which is the shortest length I could find that would work for where my oven is. I was using a 50ft extension chord at one point, and that did heat up. But the new short one I have doesn't even really get warm. The power chord doesn't seem to either, except right at this connection. I feel like I've replaced this specific crimp on connector before. So that's part of why I was assuming maybe the switch is part of the problem.
 
I'm willing to bet a proper connector will fix the issue. Make sure the switch terminal contact and screw are sanded clean, too. If the condition of the terminal is in doubt, replace the switch.
 
Stacy E. Apelt - Bladesmith said:
I'm willing to bet a proper connector will fix the issue. Make sure the switch terminal contact and screw are sanded clean, too. If the condition of the terminal is in doubt, replace the switch.
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I went ahead and put in a different switch that came with the ones I initially ordered. I have a couple new switches coming tomorrow I'll see if those perform better. I switched out the crimp on connector too. The wire is still warming up, maybe not as warm as it was getting? I let it go with no fan blowing on it for a little while.

Idk I'll put the switch I ordered in it tomorrow, and see. I just don't see why that particular spot it getting so much warmer than everywhere else.
 
"... I just don't see why that particular spot is getting so much warmer than everywhere else."
It is a point of electron friction (resistance). Something in that spot makes a narrower or more difficult path for the electrons flowing through the wire and that resistance causes heat.

There are several possibilities and remedies:
1) Switch not sufficiently rated (quite likely with low-cost Chinese import switches) - Switch out with a higher amp rated and/or better-quality switch.
2) Poor or too small lug or improper crimp - Make sure the lug is of the size and type for the current draw and switch terminal. Use a proper crimping tool, not a pair of pliers. If necessary, solder the crimp joint (use electrical solder, not acid core)
3) Improper wire size or strands cut away when stripping - Increase wire gauge by one size and cut insulation carefully.
4) Terminal installation error - The screw and terminal need to be clean and the contact with the wires secure. When using stranded wire it need to be properly twisted and tight. Screws or lugs need to be sufficiently tightened.
5) Sharp bends in the wire - Electrons are just like any other fluid flowing through a conduit. Tight bends and sharp angles increase resistance. Wires should be in smooth curves. In my old days in electronics and electrical work we used to have to put a full 360-degree loop in the wire at a terminal.
 
Well. I finally replaced the power chord with a 10 awg chord. Now they get slightly warm, but not hot like it was.

Didn't notice any change in the amount time on heat up, which I was hoping I might see. Because generally if there's heat being produced generally there's resistance. Obviously there was enough to make the wire a bit hot, but not enough make a giant difference in the performance.

Overall the kiln is doing good. The ht100 seems to have helped. I definitely recommend it to anyone that makes their own kiln.

Also moving the ceramic terminal blocks further from the chamber, and changing where the thermocouple is placed seems to have worked well.

There are likely more changes I'll make in the future. The main one I can think of now, is getter lower awg resistance wire for the heating elements.
 
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