Thanks to electrolyte for the link. From that fact sheet:
If the portable generator is providing electric power to a structure by connection via a transfer switch to a structure (home, office, shop, trailer, or similar) IT must be connected to a grounding electrode system, such as a driven ground rod. The transfer switch must be approved for the use and installed in accordance with the manufacturer's installation instructions by a qualified electrician.
Does that mean the frame of the generator must have its own grounding electrode system? In what way is the generator frame grounded through the plug/cord connecting to the home system? We have a stand-alone solar system that was approved by a state entity at the time of installation, but I wonder if that entity representative checked whether the generator was separately grounded...
@KITROBASKIN, My read is that there are two ways employ a transfer switch. More common in the scale readers in this forum would likely be dealing with are transfer switches that switch hot, but not neutral conductor. (All the neutrals are always connected.) In this case, the genset is grounded at the same place the main service is grounded and the neutral and ground are not bonded at the genset, analogous to a sub panel. You do NOT want to be bonded at two different locations which can lead to undesirable voltage and current flow in the equipment ground conductor and anything connected to it. (That means getting a shock from touching the chassis of an appliance, for example.) (When voltage and current are higher than a typical push-about portable genset at a residence, the discussion gets more complicated so let's ignore that for the moment.)
There are some situations in which you might want to have a ground electrode closer to (at) the genset since you want it close to powered equipment and perhaps to the fuel supply (nat gas pipe or LPG line). Among other considerations, a long ground conductor to the usual service ground electrode might get accidentally cut and also has a higher resistance than one closer to the the genset and xfer switch, in some peoples' views. The higher resistance can be a safety compromise.
If the neutral is switched, you must have a ground attached to the genset and the neutral and earth are bonded there since the bonding at the main service entrance is no longer available.
You may have, but do not need an earth ground at the genset if you do not switch the neutrals at the xfer switch. The advantage to the optional ground electrode to the genset frame would be lowered shock hazard if you have a fault from the hot conductors. The best earth ground is the shortest with the lowest resistance. If some equipment running on genset power has a hot to earth fault, it should trip the breaker, but it will not if the neutral is not tied to the earth in a low resistance manner. They must be bonded for the hot connection to broken by safety equipment.
The shock hazard comes in if someone's body becomes part of the lowest resistance connection from earth to neutral when a hot-earth conductor short is happening. Yes, that means that a second fault has to occur in a properly designed system. First, a fault from hot to earth, commonly called "ground", conductor. Second a relatively low resistance connection via human to the neutral. The first could be to a water pipe or some other metal connection to the soil under our feet, yes THAT earth. Now you have high voltage earth under your feet (relative to the generator). Second, maybe you touch the genset frame that is bonded to neutral and the earth under your feet. Unless you have a lousy earth, meaning green or bare conductor, connection from faulty equipment to the genset, (or an unbonded/floating genset) you should never get a shock because the breaker will have already tripped. If that has gone wrong, you could be saved by a good conventional earth connection at the genset because the breaker would have already been tripped that way or, at the very least, it should be a much better current path than your flesh and bone. Under these conditions, a ground rod at the genset could be helpful.
Hope that helps.
Neop
I don't know what the code is for burying electrical cables, but if it is below the frost line, which around here is 3.5 feet, then a power tool rental would be an immediate YES.
