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Old 05-09-2017, 07:25 AM   #9
DHeckrotte
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City: Philadelphia, PA
Country: USA
Vessel Name: Revel
Vessel Model: 1984 Fu Hwa 39
Join Date: Nov 2015
Posts: 999
With respect to marina power posts equipped with only 30 amp receptacles, and the comment above about adjacent posts powered from the same leg of a 220v main panel:

Surely, whoever wired that dock would have run feeds from both legs of the main panel. The problem becomes one of identifying posts which are wired from different legs and, if necessary, begging adjacent boat owners to trade use of the posts. A 30 amp receptacle will have three conductors: 110v, neutral, and ground; a 50 amp receptacle will have three conductors: +110v, -110v, and ground. Determining whether the 30 amp receptacles are on the same or different legs of the main panel can be done by measuring the potential between the hot conductors; it will be either 0v +/- or 220v +/-. Poking around the receptacle should not be dangerous with adequate care. Determining the hot conductor can be done by comparing the potential between the conductors. I doubt you'd trip the main panel's GFIs with your voltmeter...but, maybe.

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