Is my understanding of why ground is bonded to neutral (vs not being bonded at all) on a 3 prong dryer connection correct?

Question

I understand the need for a separate ground path back to the panel to trip the breaker on a ground fault when possible. For dryers that connect to a NEMA 10-30R, the manufacturer always indicates to bond the ground to neutral since there is no dedicated ground wire. What I'm trying to understand is the benefit of doing this vs. not bonding them together and here is what I come up with. Assume for this example I'm talking about the 120v usage from the motor and electronics.

If they are bonded together:

1. if a hot wire comes in contact with the dryer, electricity will still have a path back to trip the breaker via the neutral wire (since the dryer metal is bonded to the neutral)

2. if the neutral wire becomes detached at the breaker, you're out of luck, the dryer will become dangerously energized

If they are not bonded together:

• You are out of luck in both situations.

Is my understanding correct which is to say we bond the ground to neutral to at least account for situation 1 above which is better than being out of luck in both situations if not bonded?

Answer 1

Yeah, that's probably about right. The rationale in 1965 was that the circuits and sockets are rarely disturbed so a problem with the neutral wire is unlikely. The funerals, often with little caskets, proved otherwise.

The NEMA 10-30 / 3-wire ungrounded range and dryer connection was outlawed in 1996.

If you have any, it may not be illegal to continue them in service, but I would call it unwise. Either

• Retrofit a ground and install a 4-wire socket... or
• Supply from a GFCI breaker, and install a 4-wire socket with ground connected to nothing. The socket is labeled "GFCI Protected / No Equipment Ground".