Mike Dolt Enterprises
Mike Dolt Enterprises
User: elec_eng, Location: Portage, Indiana NEC: 2008
Asked on: Monday, March 14, 2011 at 6:04 pm EDT
Answered on: Tuesday, May 14, 2024 at 2:48 am EDT
Question: I have a building that already have (2) standby generators for optional loads. One generator is 60kw, 120/208v 3p 4w, diesel for telecom equipment and the other one is 150kw, 120/208v 3p 4w diesel for data equipment(small data center) for the building. The building has 2000a 277/480v 3p 4w service. Now the owner wants to add the third generator for some building loads. But this one will be 277/480v generator sine the loads we are supposed to back up are 277/480v.My question is this code compliance? Can you have mupltiple generators with different voltages in a single building? I feel somthing is not quite right but can't pin point the code section.
Code Compliance
Yes, it is code-compliant to have multiple generators with different voltages in a single building.
NFPA 110, the National Fire Protection Association's Standard for Emergency and Standby Power Systems, permits the installation of multiple generators in parallel if the following conditions are met: Proper Synchronization
The generators must be synchronized so that they operate in phase with each other.
Isolation Devices
Adequate isolation devices, such as circuit breakers or fuses, must be installed to prevent backfeed from one generator to another.
Voltage Regulation
The voltage regulation of the generators must be compatible so that they can operate in parallel without causing overloads or voltage fluctuations.
NEC Article 445 also recognizes the use of multiple generators in parallel and provides specific requirements for their interconnection.
Reasons for Different Voltages
There are several reasons why a building may have generators with different voltages: Existing Infrastructure
The building may already have electrical infrastructure that operates at different voltages, such as 277/480V for lighting and power and 120/208V for telecom and data equipment.
Load Requirements
The different loads in the building may require different voltages. For example, heavy equipment may require higher voltages (277/480V), while sensitive electronics may require lower voltages (120/208V).
Efficiency Considerations
Generators designed for higher voltages may be more efficient and cost-effective for certain applications.
Considerations
When installing multiple generators with different voltages, it is important to consider the following: Electrical Safety
Ensure that all generators are properly grounded and protected against electrical hazards.
Coordination with Utility
Coordinate with the utility company to ensure that the generators do not interfere with the grid.*
Maintenance and Testing: Develop a comprehensive maintenance and testing program to ensure the reliability and safety of the generators. Flag for review