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I am feeding two 200 amp panels with a 32kw generator using an auto transfer switch. To prevent unsafe generator start up can I wire the utility sensing control using power from each panel to the sensing fuses making sure I have correctly phased each terminal? The utility is 400 amp single phase 240/120 volt service feeding the auto transfer switch. Transfer switch feeds each 200 amp panel with 3/0. If I feed the transfer switch utility 240 volt sensing circuit from say panel 1 and the panel is shut off it would cause the generator to start. Thus I need both panels to connect to this circuit. – Mike yesterday

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    Is one a sub-panel of the other? Other than that and the service grounding, do you have any cross-wiring of any kind between the two panels, any place they share hots or neutrals, or a hot comes out of one panel while neutral goes back to the other etc.? – Harper Mar 6 '17 at 17:08
  • We'll need way more details about your setup here... – ThreePhaseEel Mar 6 '17 at 23:17
  • The utility is 400 amp single phase 240/120 volt service feeding the auto transfer switch. Transfer switch feeds each 200 amp panel with 3/0. If I feed the transfer switch utility 240 volt sensing circuit from say panel 1 and the panel is shut off it would cause the generator to start. Thus I need both panels to connect to this circuit. – Mike Mar 8 '17 at 13:17
  • How many circuits total do the two panels feed, and how many can they feed? It seems that using a single 400A panelboard is the simplest way to solve this problem (splitting panelboards used to be needed under pre-2008 NEC editions due to the 42 circuit limit, but that limitation is no more, and you can get single panelboards up to 60 or even 84 circuits nowadays) – ThreePhaseEel Mar 9 '17 at 23:13
  • Yes ThreePhaseEel this would be the best. However I did not become involved in the project until the panels were installed. I have considered installing a control relay using NO contacts from panel one and NC from panel 2. – Mike Mar 10 '17 at 14:04

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