Anyone know what is the code section for a non-separately derived system (generator on a 3-pole transfer switch, not switching the neutral) that says making a grounding connection at the generator is not allowed?
What happens if you DO make a grounding connection here?
A grounding connection means what?
If you are asking what about connecting to an electrode then there is nothing wrong with this and some generators have an external lug for a connection to an electrode no matter if it is being installed as a SDS or a NON-SDS.
If you are asking about bonding the neutral to an electrode or the supply side bonding at the generator then there will be a parallel path for the return current. Article 250.35 permanently installed generators was introduced in the 2008 code cycle and the bonding conductor between the generator and the transfer was referred to as the equipment bonding conductor.
On a NON-SDS the neutral is bonded at the service and on a SDS the neutral is bonded at the generator. It is not bonded at both places.
Depending on the type and size of the generator and the rules adopted by your state the installation instructions included with the listing of the generator come into play. If this is a generator that is portable and is being connected by a cord plugged into a receptacle on the frame of the generator then UL FTCN states that it must be installed as a SDS.
This category covers internal-combustion-engine-driven generators rated 15 kW or less, 250 V or less, which are provided only with receptacle outlets for the ac output circuits. The generators may incorporate alternating- or direct-current generator sections for supplying energy to battery-charging circuits.
When a portable generator is used to supply a building or structure wiring system:
1. The generator is considered a separately derived system in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).
2. The generator is intended to be connected through permanently installed certified transfer equipment that switches all conductors other than the equipment grounding conductor.
3. The frame of a certified generator is connected to the equipment-grounding conductor and the grounded (neutral) conductor of the generator. When properly connected to a premises or structure wiring system, the portable generator will be connected to the premises or structure grounding electrode for its ground reference.
4. Portable generators used other than to power building or structure wiring systems are intended to be connected to ground if required by the NEC.
Article 250.34 states that portable generators are not required to have an electrode system if the adhere to the conditions outlined in 250.34(A)(1) and (2)
