Mike Dolt Enterprises
Mike Dolt Enterprises
User: charlie b, Location: Lockport, IL
Asked on: Wednesday, April 6, 2011 at 11:20 am EDT
Answered on: Tuesday, May 14, 2024 at 3:50 am EDT
Question: I have a generator that will supply, among other things, a fire pump. The present site plan shows it located on the same concrete pad as the utility transformer. Does that violate the rule about a fire in one source not causing an interruption in the other? The NEC does not give specific separation requirements, but does anyone know of a rule (or a rule-of-thumb) regarding minimum distances?
NEC Rule
The National Electrical Code (NEC) does not have a specific rule regarding the separation of a generator from a utility transformer. However, Article 700.12(F) states that generators should be installed "in a manner to minimize the probability of a fire from any source originating outside the generator causing an interruption of service."Industry Recommendations
Various industry sources provide recommendations for separating generators from other equipment, including utility transformers. NFPA 110
Standard for Emergency and Standby Power Systems, recommends a minimum distance of 6 feet (1.8 meters) between generators and other equipment.
IEEE Std 1100
Recommended Practice for Installing and Maintaining Industrial and Commercial Power Systems, suggests a separation distance of 10 feet (3 meters) between generators and transformers.
Underwriters Laboratories (UL)
UL Standard 2200 for Generators requires a separation distance of 5 feet (1.5 meters) between generators and other equipment.
Rule of Thumb
A common rule-of-thumb is to maintain a minimum separation distance equal to the largest dimension of the equipment.
Consider the following factors
Fire hazard
The proximity of the generator to the transformer raises concerns about the potential for a fire in one source spreading to the other.
Maintenance access
Adequate space is necessary for maintenance and inspection of both the generator and the transformer.
Electrical hazards
Close proximity can increase the risk of electrical arcing or interference.*
Code compliance
Although the NEC does not explicitly address the separation distance, it requires the installation to minimize the risk of service interruption.
Recommendation
Based on these recommendations and the rule-of-thumb, a minimum separation distance of 10 feet (3 meters) between the generator and the utility transformer is advisable. This distance would provide sufficient protection against fire hazards, allow for maintenance access, and minimize electrical risks.
Note: Local codes or regulations may have additional requirements for the separation of generators from other equipment. It is essential to consult with the local authority having jurisdiction for specific guidance. Flag for review