445.11 Marking.
Code Change Summary: Marking requirements for generators have been simplified and placed into a list and two new line items were added.
In the 2017 NEC®, inverter-based generators that are stationary or portable and rated more than 15kW are now required to be marked with the maximum short-circuit current to assist the inspector and installer when verifying proper overcurrent protection in the field.
Newer generators are becoming quite complex. Especially the newer variable speed inverter based models. Determining short-circuit current ratings (SCCR) for these generators is difficult and is best left in the hands of the manufacturer.
Marking is also now required to indicate whether the generator is inherently designed to prevent an overload or whether an overcurrent protective relay is provided. This information will assist the AHJ in determining conductor ampacity as required in 445.13.
In the 2014 NEC®, marking requirements were added to make it easier to determine in the field if a generator is wired as a separately derived system. Knowing this determines what type of transfer switch to install and where to locate any required grounding electrodes per 250.35 and 250.30. These requirements were cleaned up a bit in the 2017 NEC® but the basic concept still remains.
When the inspector arrives for the generator inspection, several things will be considered:
- If the system is being used as an emergency system, legally required or an optional standby system.
- Type of transfer switch being used to ensure it is compatible with the type of generator system.
- Whether or not the generator is wired as a separately derived or non-separately derived system and the location of any system bonding jumpers that may be present.
Often when trying to determine if a system bonding jumper is installed, the electrician will end up removing multiple body parts from the generator while trying to find the right compartment where a system bonding jumper may be located. The marking requirements greatly assist in avoiding this type of situation.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC® edition of NFPA 70.
2014 Code Language:
445.11 Marking. Each generator shall be provided with a nameplate giving the manufacturer's name, the rated frequency, the number of phases if of ac, the rating in kilowatts or kilovolt-amperes, the normal volts and amperes corresponding to the rating, the rated revolutions per minute, and the rated ambient temperature or rated temperature rise.
Nameplates for all stationary generators and portable generators rated more than 15 kW shall also give the power factor, the subtransient and transient impedances, the insulation system class, and the time rating.
Marking shall be provided by the manufacturer to indicate whether or not the generator neutral is bonded to the generator frame. Where the bonding of a generator is modified in the field, additional marking shall be required to indicate whether the generator neutral is bonded to the generator frame.
2017 Code Language:
445.11 Marking. Each generator shall be provided with a nameplate giving the manufacturers name, the rated frequency, the number of phases if ac, the rating in kilowatts or kilovolt-amperes, the power factor, the normal volts and amperes corresponding to the rating, the rated ambient temperature, and the rated temperature rise.
Nameplates or manufacturers instructions shall provide the following information for all stationary generators and portable generators rated more than 15 kW:
(1) Subtransient, transient, synchronous, and zero sequence reactances
(2) Power rating category
(3) Insulation system class
(4) Indication if the generator is protected against overload by inherent design, an overcurrent protective relay, circuit breaker, or fuse
(5) Maximum short-circuit current for inverter-based generators, in lieu of the synchronous, subtransient, and transient reactances
Marking shall be provided by the manufacturer to indicate whether or not the generator neutral is bonded to its frame. Where the bonding is modified in the field, additional marking shall be required to indicate whether the neutral is bonded to the frame.