www.TK560.com

[TroyO]

Just a progress update:

I have the shell made, drilled and all the ceramic donuts are mounted.

Most of the coils are in... well, almost. I was just going to use regular copper/tin ring terminals but have since reconsidered and am waiting on the arrival of some high temp nickel/steel ring terminals. I can do that without unstringing the coils though, so there's really only one left to do.

My latest debate is about how exactly to wire it. I have a couple of 270V/10A rated SPST (Single Pole, Single Throw) switches. I can connect Hot1 to one side of the coils, and just switch Hot2 to the other side to turn them on/off. The problem is that then HOT1 is always connected... with 120V charge relative to ground. That doesn't neccesarily cause a problem as long as you never touch the coils (And ground) when it's plugged in. (IE... plugged in but off still = dangerous.)

I have been looking in to buying two DPST (Double Pole, Single Throw) switches that would cut both sides of the circuit at the same time.... it would be ~$20. Not sure if it's really worth it... just make sure to unplug it when done. (I always did anyway.) You'd kind of have to "Try" to get to the bad parts anyway.

The next quandry is about putting an expanded metal grid below the coils. That would trap the coils in a grounded shell (But not touching) ... max safety even with single pole switches. You can't get to the coils then, and if any of the coils did let go it would pop a breaker. (GFCI)

Would that help even out the heat, or just block it? I suspect it would get hot after a bit and radiate it's own heat... maybe longer to warm up but just as hot. Anyone have input, advice or links to a thread where it's been done?

Camera (And pics) are at home, so I can't do the pics yet but will try to get them posted and a quick description of what I have done so far.

[spektr]

Why dont you look at a main disconnect switch? It is SO MUCH safer to be able to kill the machine without unplugging it or worrying about whats hot where with switches in what position. I see some in Home depot for around 30 bucks...... Usually they are installed for stuff like hot tubs and such........ try the link.. Scott

http://www.grainger.com/Grainger/items/1H245

[cod]

If you are using a GFCI outlet- doesnt that have a breaker ? Mine does. I basically have 2 circuits with hardwired plugs that go into a 4 hole gfci box which is mounted on the machine. I can pull the plugs from the box and I have a clear visual representation that my oven is not plugged in. I could also trip the breakers on the gfci's by hitting the 'test' buttons which trips the built-in breakers.

http://cjod.net/cpg/displayimage.php?album=2&pos=10[/i]

this is an old photo - I've since mounted the box directly over the hole where the leads poke out of the oven and gotten rid of the sharp corners with a metal grommet.
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[TroyO]

Actually, the GFCI is the main breaker to the garage... so if it goes, eveything goes.

Anyway... found 10A 250V DPST switches at Radio Shack, of all places. They are little round guys that will be easy to mount. I usually think of them for small electronics, not for stuff with houshold ratings. They are small switches but the rating says they are up to it. Only $3 each too. I also picked up two neon indicator lights... rated for 120V, so I'll have to put a reststor on them but I'll have individual coil-on lights too.

Switches:
http://www.radioshack.com/product/index.jsp?productId=3016149

Lights:
http://www.radioshack.com/product/index.jsp?productId=2102793

So I think I'm set for wiring... no live parts when the coils are off, although there will be 120V to ground when either coil is turned on. I'm figuring the hot coils and lights will be enough to keep folks hands off, though.

[TroyO]

It's been a while, real life has thrown me many distractions but I finally was able to get back on task this weekend.

I finished up the oven.. at least to the functional stage. I have been taking pics, but haven't had a chance to sort through them yet.

All in all, it went mostly as planned.

A couple of notes:

The ceramic spacers used to enter and exit the shell worked fine except for one unforseen issue. They have really NO give, so the first time I fired up the oven one of them shattered as things heated up and expanded. It was a pretty nice craking sound and I found bits several feet away. I added a couple of washers between the post and the cap so that even when "tightened" down they still had a little wiggle on the shell.

The switches I posted were specc'ed to handle the load but they are cheap and it was hard to wire in the little spade connectors. I went to Ace Hardware and picked up some DPST toggle switches rated at 10A/220V. They had much nicer screw terminals.

You can use 120V neon lamps on 220V by looking at the built in resistor on one leg of the lamp and soldering the same value resistor in series with one lead. (Or, replacing the existing one with a double value resistor.) It was a 33K on the one I got at Radio Shack.

Anyway... I still need to add the thermal insulation and the silicone gasket but functionally it's operational. The circuit I posted worked just fine. The 1200 Watt coil gets just barely to a visible glow. The 2000 Watt coil glows pretty good, about like a toaster.. maybe a tad less.

Heat range seems to confirm the power output... the 1200 Watt would probably not melt most plastics.. at least not quickly. The 2000 Watt coil probably would work by itself, especially after everything was fully up to temp. With both on it should do thin plastincs really quickly.

So, there ya go... nested coils, 3 heat levels (1200/2000/3200) in a stainless shell. I'll post pics as soon as I get a chance to go through them and grab the best for each stage of the project.