Need advise on wiring an oven

I purchased an electric heat treat furnace that is wired for 3 phase 460 volts. It has three separate heating coils. Each of these coils has one end wired to each of the three legs of the three phase 460 line. The other end of each of the coils are wired to each other making a serial type connection. I am wondering if I could wire the three elements to 240 volt single phase by putting the elements in parallel to each other. If this will work what would my current draw be. It presently pulls 14.5 amps on each leg using 460.

You have a wye resistor three phase network. The power for the 460 volt wye setup running on 460 volts three phase is:

Power = volts * amps * 1.732 (square root of 3)
Power = 460 * 14.5 * 1.732 = 11,552 watts for the 3 elements.

Now if you ask what is the voltage across any resistor in the above situation, it is:

460 volts / 1.732 = 265 volts.

This means each of the three elements is 'rated', as it were, for 265 volts single phase, which fortunately is ABOVE 240 volts, which means you CAN do what you want without burning up your elements too quickly (in fact, they'll actually last a bit longer!)

Now, you won't get quite s much power this way. Here's where this calculation becomes a bit uncertain, as a heating element is a nonlinear resistor (resistance goes WAY up with red heat compared to room temp).

If we ask what is the resistance at full heat of any one resistor,

R = 265 volts / 14.5 amps = 18.28 ohms

At 240 volts, the current across one resistor would be

i = 240 / 18.28 = 13.13 amps for ONE element.

The power across one element would be

P = volts * amps = 240 * 13.13 = 3151 watts.

So for THREE elements in parallel, the total power would be about 9453 watts, which is down about 2 kw from your three phase situation. The oven won't get quite as hot, and will take slightly longer to warm up.

You'll need at least a 40 amp breaker (3 * 13.13 amps) on that circuit, and i'd recommend a 50 amp with at least AWG 6 wire feeding it.

One more thing . . .

If you really want to push the oven to do what it would on 460 volt three phase, you could get yourself a 1.0 kva buck/boost transformer which would boost the 240 volts single phase to 264 volts. Cost about $200 at Grainger. About as perfect a conversion as you can get.