I am replacing my hot water heater with one almost identical to the old one.The old one had a black and a red and a ground wire. The new one is the same. They are both 50 gal electric. The new one trips the breaker(basically it won't even let it engage). I assume my water heater is bad. It is a dual element like the old one was. Of course I am filling the heater with water before I try the breaker. The wiring in my house has a black and a white and a ground. I hooked the black to black and the white to red and the ground to the green ground screw on the heater. I also verified that the ground from the heater was secured tightly. I looked on the info labels of both heaters and verified that they are the same. I forgot to mention that the old one did work just fine but it was 15 years old and time had taken its toll on it. I figured that it was just a matter of time before it gave me trouble and I was remodeling the area where it is located. The house is actually an old mobile home that I bought and am remodeling so I can move to the country. What kind ov voltages should I read between the black and white and ground wires in the trailer? I think it read about 240v between the black and the white. Thanks in advance for any help you can provide me.

You are describing a dead short, when the breaker won't reset at all. If you have wired the heater correctly, If I may ask, where are you getting the voltage readings if the breaker won't hold? If your wiring is correct it's possible the heater is wired wrong, or one on the wires is actually touching the tank creating a short. A shorted element is unlikely, since they USUALLY burn through, but the elements can be checked with an ohmmeter with the power OFF and the feed disconnected.

Try disconnecting the wires at the water heater. Cap the ends and turn the breaker on, if it trips then the problem is most likely in your existing wiring. If not then it's obviously something in the heater.

The voltage readings I took were on the existing wires in the trailer with the water heater unhooked. The breaker works fine until the heater is wired in.