Eric:
Here is another distinction to make: 1. In PG&E territory, the largest service that is direct metered is 320 amps (continuous). This may be likely in many other areas. 2. Above that, the metering is all done with CTs (current transformers). 3. If you pull a direct meter, you disconnect the feed to the service. 4. Fire responders and line workers will pull the meter as a foolproof way to disconnect a service. 5. If you pull a CT meter, you do not disconnect the service. 6. If you have a CT service and a grid-interactive system in PG&E territory (and likely many other utilities) you have to install a locking disconnect within 10 feet of the service disconnecting means that disconnects the grid-tie or the entire feeder. 7. The information above was derived from many sources and should be verified. The service you are describing is likely a class 320 direct metered service. Here is a link to information on a common variety. http://www.hqs.sbt.siemens.com/gip/general/dlc/data/assets/us/SIILV/Brochure _400A_Combinations_Siemens.pdf I hope this information helps (and is not something you already knew). William From: [email protected] [mailto:[email protected]] On Behalf Of Chris Mason Sent: Thursday, December 19, 2013 2:41 PM To: RE-wrenches Subject: Re: [RE-wrenches] Busbar rating with multiple main breakers The 120% rule refers to source breakers, not load breakers. On Thu, Dec 19, 2013 at 3:16 PM, SunHarvest <[email protected]> wrote: Hi guys - Concerning the 120% rule: I've encountered several circumstances recently where a 400A nameplate-rated (listed on inside label) main panel has two 200A main breakers. One of the breakers will be feeding the busbar in the main and the other will feed a subpanel. I had previously thought the main busbar is rated at the nameplate rating (400A in this case) regardless of quantity of main breakers. My lead electrician says the main busbar in these types of panels is derated to 200A because of the split. However, I have two other reliable electrician friends who disagree with my lead electrician. One of my C10 buddies says it depends on whether or not the busbar in the main is broken up into 2 sections (200A) or it is continuous (400A). Can anyone clear up, beyond doubt, our disagreement? Thanks! Eric Stikes SunHarvest
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