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captmike
Novice


Joined: 01 May 2012
Posts: 27
Location: Elberton, Georgia

PostPosted: Fri Jun 01, 2012 8:45 pm    Post subject: While I'm Waiting.... Reply with quote

Until I get everything in order to build my bigger unit, I need to upgrade the oven on the 12 x 12 I built. The skillet just will not do the job on .030 or thicker plastic and I really need to complete tests on a mold I am building. I disassembled my toaster oven (again) and removed the cal-rods in hopes I can revamp my oven enclosure. Here is what I have so far:



The plywood is for planning purposes only; I will use metal brackets to hold the rods. My oven box is approximately 12 x 12 and the elements will cover about 8 x 11 spaced 2.25 inches apart. The box is about 6 inches deep and lined with concrete board ( I know, but that is what I had available and & it will be for test purposes only).



What I need to know is how to wire the elements and what kind of controller I will need. The one on the toaster oven looks complicated and all I really need is for the elements to come on and turn off ( I think). I can build the brackets to hold the ceramic parts. Suggestions?
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jdougn
Guru


Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Jun 11, 2012 6:16 am    Post subject: Reply with quote

110 volt or 220 volt wiring?
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crashmann
Guru


Joined: 27 Sep 2005
Posts: 501

PostPosted: Sun Jun 17, 2012 8:20 pm    Post subject: Reply with quote

You'll need to measure the resistance of the cal rod heating elements using a multimeter. If you pulled them out of a toaster oven, then they most likely ran on 110 volts AC. I can't imagine a small counter top toaster oven pulling a heavy load to pop a 15 amp circuit breaker, but we won't know until you provide the resistance reading.

If the resistance is too low, then the heater coils will allow too much current to flow and you will pop the circuit breaker feeding the electrical outlet.

Ohm's Law:

I = V / R

Current = Volts / Resistance

The rule of thumb is that you do not want to run more than 80% of the capacity of the circuit breaker. For a 15 amp circuit, you don't want to exceed 12 amps. Also, you've got 2 cal rods running in parallel, effectively cutting the resistance in half. Therefore, you should read at least 20 ohms of resistance for each set of cal rods in series:



12 amps = 120 volts AC / 10 ohms <--- this is the resistance you measure on the coil divided in half. Anything lower, and you're in trouble!

To connect everything together, you'll need some 12 gauge wire (a 12 gauge extension cord is perfect), a double pole double throw electrical switch, and an electrical box to mount the switch.

Here's what your wiring will look like:



White is "hot"
Black is "neutral"
Green is "ground"

Chop 5 feet off the end of the extension cord to use for the wiring from the switch to the cal rod heating elements.

Disclaimer

Of course, you get what you pay for, and you don't pay for the advice on the Internet. Be sure to follow all kinds of safety precautions:
Connect the green ground wire to any metal in the system, including the aluminum foil at the bottom of the oven
Check your connections with a multimeter to ensure that you do not have any short circuits
Plug into a GFCI outlet
Wear leather gloves
Have a fire extinguisher at the ready
Use a chicken stick to turn on the power switch

If it works, and you don't burn down your house, post the results so that others can learn from your experience.

Charlie
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jdougn
Guru


Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Mon Jun 18, 2012 6:18 am    Post subject: Reply with quote

Crashmann, that is an excellent response. Can't imagine how it could be any better. Thanks for the effort.
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spektr
Master


Joined: 07 Jan 2008
Posts: 425

PostPosted: Mon Jun 18, 2012 6:56 am    Post subject: Reply with quote

Well said..
As usual, youre on form...

Scott
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