I am replacing the wiring of an old house( partially burned),some of the 220v appliances such the stove and the clothes dryer have only 3 wires( black, red and white), I think (not sure) the house is grounded through the water copper pipes( the white wire-the neutral- is connected to the ground bar in the panel) . My first question is : do I need to run a dedicated ground wire for each appliance or I can leave the old wire connected as they are( keeping the neutral connected to the ground)?My second question is: do I need to install a grounding rod to supplement the existing grounding which I assume is connected to the water pipes ? Thank you
If you are replacing the wiring (after a fire, I guess you mean by "partially burned"), I believe the normal standard is to meet the current codes at the time of replacement, not the code at the time of the building construction.
As such, you will need 4-wire service (hot, hot, neutral, ground) to 240V appliances that use the neutral. 240V appliances that don't use the neutral only need hot, hot, and ground.
You will also need to bring the grounding system up to current applicable code.
My sense from your question is that you might want to self-educate a bit more, or consult with an electrician in the planning stages, rather than have to re-do stuff later from improper planning now.
It sounds like only the appliances were damaged. If the wiring was not damaged code allows it to continue to be used replacing an outlet with the same type is allowed. Usually the grounding system only requires updating with a panel upgrade. However I have run into several houses that the water mains were replaced with plastic pipe and ground rods needed to be added.