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Isolation transformer and connection to ground
I can't agree, Steve.
The question involves safety not electrolysis. It is well understood that there must be no connection between the grounds to eliminate the electrolysis currents and that is the primary reason for installing a transformer. However considering the safety question, the concern is the (remote) possibility of a short from the primary winding to the frame. I disagree with your statement that a fault on either side of the transformer will trip the circuit breaker - that is incorrect. If, as has been suggested, the transformer frame is connected to the boat ground and you develop a fault from the primary winding to the frame - and hence the boat ground - and hence the underwater metal, you will NOT draw enough current to trip a 30 or 50 amp circuit breaker. The underwater metal will be alive at a high AC voltage and considerable current will be flowing to the water generating all sorts of nasty gasses but there is no way the water is going to carry enough current to trip the breaker. A swimmer in the vicinity is then at risk of a lethal shock. As Chuck pointed out, a GFI will disconnect as soon as it detects leakage current to the water but GFI outlets on the dock are very rare and GFI protection on the boat input side of an isolation transformer is virtually non-existent. A short from the secondary side to frame, if the frame is connected to either shore or boat ground is a far less critical situation since the secondary side is floating so no lethal voltage would be present on the underwater metal in either case. Regards, Andina Marie Foster, |