Mike Dolt Enterprises
Mike Dolt Enterprises
User: mccayry, Location: Tennessee
Asked on: Thursday, June 2, 2011 at 3:12 pm EDT
Answered on: Tuesday, May 14, 2024 at 6:08 am EDT
Question: Im looking at a house that has a 150A service. The HO has a Siemens 200A meter/panel combo he wants to install. The combo panel is equipped with feed through lugs so my thoughts were to install the meter/panel and feed throught to the existing 150A panel located inside. My question is do I consider the existing panel a subpanel and if so should the nuetral and ground be isolated? In the existing panel the grounds and grounded conductors are all terminated together so I would need to separate them.
Consideration of Existing Panel as a Subpanel
Yes, the existing 150A panel is considered a subpanel when the meter/panel combo with feed-through lugs is installed.
Isolation of Neutral and Ground
According to the National Electrical Code (NEC) 250.24(A), the neutral conductor and equipment grounding conductor (EGC) must be isolated at the main service panel. This is not required at subpanels.
Separation of Grounds and Grounded Conductors
Since the grounds and grounded conductors are currently terminated together in the existing panel, you will need to separate them: Use a busbar or terminal block to separate the neutral bus from the ground bus. Reclassify any wires that were previously connected to the combined bus as either grounded conductors or equipment grounding conductors. Install a green screw or clamp to terminate the equipment grounding conductors on the ground bus.
Additional Considerations Ensure that the feeder conductors from the meter/panel combo to the existing panel are sized appropriately for the amperage of the subpanel. Install a main breaker in the subpanel with an amperage rating equal to or less than the amperage of the feeder conductors. Label the subpanel as a "Subpanel" or "Branch Panel."Recommended Procedure1. Install the meter/panel combo and feed through to the existing panel.
2. Separate the neutral and ground terminals in the existing panel.3. Label the existing panel as a "Subpanel." Flag for review