I am replacing the range in my kitchen with a free standing range. The old range was a electric cook top with a separate wall oven. The old oven and stovetop were connected to a breaker box behind the cabinet which was connected to a junction box near the floor. I removed the breaker and junction box and all wiring. Now all I have coming through the floor is the main wiring. There are 3 wires:red, black and white, no ground. Do I attach a 3 prong recepticle to this or does it have to be 4 prong? There is no ground wire. And get a 3 prong cord for my stove? Will it be grounded? Sometimes I would receive a slight shock from the stove if I touched the sink at the same time. I was told that the stovetop was going bad.
There is a provision in the National Electrical Code that will allow a 3-wire installation, in situations where there is existing wiring (250.140 exception). You should be fine to install a three prong receptacle, and use a three prong range cord.
There should be special instructions in the manufacturer's installation instructions that are included with the range, that will specify exactly how to attach the 3-wire cord.
If you're really concerned about it, or want to update to follow modern code. You could install a new 3-wire with ground cable, and use 4-prong receptacle and cord.
National Electrical Code 2014
Chapter 2 Wiring and Protection
Article 250 Grounding and Bonding
250.140 Frames of Ranges and Clothes Dryers. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.
Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met.
(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.
(2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE serviceentrance cable and the branch circuit originates at the service equipment.
(4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.