北京市自动驾驶测试车辆正式上路测试

Question

My new detached garage will have a 200 amp panel. I wanted the incoming power to be under ground. This will require boring 160 ft. using 3” conduit. I was told 3” conduit for boring is a non-standard size. My contractor is trying to find a remnant. A minimum order is 5,000ft.

I was told the local power company won’t allow two parallel 2” conduits to feed my panel in this application because it’s 3 phase power. What would be the technical reason for not allowing this?

I don’t plan to fight the power company, I just want to understand if there is a technical reason for this? All they would say is, that’s what we require.

Answer 1

The power companies usually run a 4/0 or 1/0 quadruplex service cable similar to the picture below for a 200 amp 3 phase residential service. All four cables are on one reel and wrapped around each other so they can only be pulled in one conduit.

If they were out of the 4/0 quad, they would run individual conductors but all three phases, neutral and ground would need to be in the same conduit to balance the magnetic fields generated and to reduce overheating of the conductors. For very large services, they could run parallel three phase circuits with each circuit in it's own conduit.

This type of service would only be done in rare circumstances for single family residental homes, USA, where special equipment in the home required it and then a customer contribution would peobably be required.

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