Mike Dolt Enterprises
Mike Dolt Enterprises
User: Jameslopez, Location: Tennessee
Asked on: Sunday, April 3, 2011 at 12:06 am EDT
Answered on: Tuesday, May 14, 2024 at 3:41 am EDT
Question: I recently had to visit a dairy to consult about a possible PV installation. It surprised me when the dairy supervisor told me that he was worried about someone working in his Main because they might tie his ground and neutral together there and give him stray voltage problems. He informed me that his neutrals and grounds are separate in his main. I've worked in commercial electrical for most of my carrier but I never assume I know everything. I assumed that like most installations I've ever seen you have to bond your neutral to ground at your main and separate it thereafter. Is it allowable to keep the neutrals and grounds separate at the Main in a Agricultural installation? The panel was a old Zinsco 400A stand up switchboard and with a 3 phase 240v service which I'm also assuming has a stinger due to the fact that every third breaker space was empty
NEC Code Allowance
According to the National Electrical Code (NEC), it is allowable to maintain separate neutrals and grounds in the main electrical panelboard for a single-phase agricultural installation.
Article 250.36 of the NEC states: "For single-phase services, the neutral conductor shall be bonded to the equipment grounding conductor at the service entrance or transformer."Explanation for Agricultural Exemption
In agricultural settings, it is sometimes necessary to keep neutrals and grounds separate to prevent stray voltage problems in livestock operations. Stray voltage occurs when electrical current flows through the ground, creating a voltage potential that can harm animals.By separating the neutrals and grounds at the main, it helps to isolate the electrical system from the grounding system and reduces the risk of stray voltage.
Specific Considerations Phase
The NEC allowance for separate neutrals and grounds only applies to single-phase agricultural installations. For three-phase systems, the neutral must be bonded to ground.
Panel Type
The type of main panelboard must be compatible with separate neutrals and grounds. Some panel types, such as Zinsco panels, are not designed for this configuration.*
Stinger Service
A stinger service, as you mentioned, is a single-phase service with only two wires (hot and neutral). The third wire (ground) is not connected at the transformer. In this case, the NEC requires a grounding electrode to be installed at the building to provide a ground reference.
Recommendation
It is recommended to follow the NEC code and the guidelines from the dairy supervisor. Before making any changes to the existing electrical system, it is always advisable to consult with a qualified electrician to ensure safety and compliance. Flag for review