I am installing a new Bosch dishwasher and my current wiring has no ground wire. Also it comes with a junction box and special plug to supply power to the unit. Just wondering how to properly ground it and if it will work at all without the ground
The dishwasher does not know if you have a ground or not. The ground wiring on the inside of the machine (the dishwasher in this case) is tied to everything that will conduct electricity easily and could come into contact with the user; typically anything metal.
A ground wire can be thought of as simply a backup neutral. So if a hot wire ever touches some part of a metal system, the current will have this backup wire to run the current back to the breaker box. The breaker will detect this increase in current (unimpeded path) and trip which will cut off power to the device. If this wire weren't here, the metallic object would be energized, but it would not trip a breaker. It would simply be waiting for something (a person) to come along and touch it to give it a better path to ground.
So, as long as a hot never comes loose, you wouldn't need the ground. But if it ever were to, this wire could save a life (or prevent a really strong tingling sensation).
To shorten things off and end this; you don't need the ground for the dishwasher to function. It will work perfectly fine without one and you just wouldn't connect the ground wire on the other end. You then run the risk of a wire coming loose though.
But, what should be done regardless and will also provide grounding functionality is to use a GFCI breaker. The breaker would replace the existing breaker feeding the dishwasher and include a pigtail to the neutral. This breaker detects the current that is feeding into the circuit and out of the circuit. As long as everything is running like normal, it will work like a normal breaker. However, if a hot ever comes loose, the GFCI would detect that current is going in, but not as much is coming out and the breaker would trip itself.
I installed a Bosch 500 series dishwasher approximately 45 days ago so I am familiar with the setup that has been provided to you. In terms of making the connection to the dishwasher itself they have made it extremely user friendly with the plug-in cord, however, you still must provide safe and appropriate wiring in your home to connect to the Bosch-supplied plastic junction box. It is unsafe to operate your dishwasher without appropriate grounding. Not only that but your warranty will likely be void.
Unfortunately the only safe solution is to either run a dedicated ground wire from the provided junction box all the way back to the main panel, or replace the existing house wire that supplies the dishwasher with modern 14/2 Romex wiring, which includes a ground wire. Either way, I recommend hiring a licensed electrician to make the new wiring run for you as the ground wire will need to be safely integrated into your main service panel.
Some may say that it is acceptable to ground the circuit to a nearby cold water pipe - this is unsafe and was disallowed by code in 1993 due to the possibility of non-metallic connectors used in your water supply.
Just installed a Bosch 300 series which required the dedicated ground. Problem solved by installing grounding rod (Lowes/ Home Depot) & grounding rod clamp. The rod itself is approximately 7' in length. You will also need 12 or 14 gauge wire (single strand). Make sure you have a mini sledge hammer. This also allowed me to ground my adjacent stove which had an optional ground. Sleep easier and do it right. It will also void warranty if it wasn't properly grounded so take heed.