Everything you need to know about neutral bonding/ grounding (probably)
Bonding neutral is really quite simple, but until you get it, it can seem confusing. Here's all you need to know. Bonding just means connecting. People use the term 'floating neutral', but we really should just call it bonded or not bonded.
Very simply, bonding neutral is just connecting neutral and grounds at some point. It is done at one, and only one point in a system, with some specific exceptions that will rarely apply to us at home. Most homes and buildings will have neutral bonded in the main breaker panel, and sometimes in a disconnect switch outside.
We bond the grounds to neutral for a very simple reason, the grounds won't do their job otherwise. Their job is to act as a back up neutral, providing a good, separate pathway for stray electricity to get to the neutral leaving the building or system. The grounds of the wiring system are connected to the chassis/ frame/ or body of appliances and fixtures. This is done to provide a path for current to flow that takes it back where it belongs should the wiring short to something in order to flow enough current to 'clear' or trip the protection device (breaker or fuse). Otherwise the power could energize things we don't want energized and then hurt someone when they touch the appliance, or start a fire.
We bond ground and neutral in only one place because if it were in more than one place, the ground wire between the points would be parallel to the neutrals they are connected to and carry current any time the circuit was being used, and that's not good. You may have heard of the concept of 'current on the grounds' or something similar, and this is what they're talking about.
Portable generators will normally come with the neutral bonded, because they are normally used as standalone power systems, so this ensures the grounds will function correctly. When we connect our generator to an existing system that already has the neutral bonded, we should not have it bonded at the generator. If it were, the ground between the generator and the other system will parallel our neutral and carry current, which it should only do in a fault condition.
This all should not be confused with earth grounding. That's the usually bare wire running to a ground rod outside your house. That connects to neutral also, in only one place, but it serves a completely different purpose and has nothing to do with the equipment grounds and neutral. It's job is to dissipate the energy of nearby lightning strikes (lightning doesn't have to hit your house to impart energy on it). It is not necessary, and probably a bad idea, to put a ground rod on your generator, unless it is setup as a standalone system in a permanent installation. If you have a generator hooked to your system, and that system has an earth ground rod, the existing earth ground does the job just fine. If you have a generator setup somewhere as a standalone system that is semi-permanent or permanent, it needs a ground rod hooked to neutral to protect it which can be done on the system or the generator.