Temporary shore power

Colvic Watson

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Need to work on the boat and it means leaving a small heater and dehumidifier on board to enable preparation and curing. Thought I could just connect up to the pontoon power and put an RCD device on the socket end in the boat for protection. Question is - will this affect galvanic corrosion?

Power lead from shore to boat, no connection to on boat 12v power or engine, no connect of 240v lead to boat, only to heater/dehumidifier which will sit on the main cabin floor.

Thanks for your advice.
 

VicMallows

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Technically, if the mains powered equipment is totally isolated (electrically) you have nothing to worry about as far as galvanic action is concerned. But do make sure your feed to the heater etc is protected by a shore-based RCD (residual current device) . (used to be called an Earth Leakage Circuit Breaker, ELCB)

Vic
 

david_bagshaw

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wont be any problem as you discribe.

However if the dehumidifier is metal & sits in the sink & you have metal plumbing then there is a "connection"
& the possibility of problems.
 

aidancoughlan

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Vic, I notice your comment "But do make sure your feed to the heater etc is protected by a shore-based RCD (residual current device) "
Does this mean that the RCD device should not be physically on the boat?

I got the impression that Simon was just going to bring a shore-power lead on to the boat, and put a RCD (on board) & probably wire a single socket on the end. I've inherited the same arrangement (without the RCD), and was planning to add it for protection. Is it sufficient to just purchase an RCD on board?

dont mean to hijack the original question about galvanic corrosion, just wondering about the RCD comment...
 

fireball

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It doesn't matter where the RCD sits as long as it isn't too far down the line (at the other end of the pontoon!). But I'd trust one I own over someone elses!
You can just buy the plug in ones in B&Q ... short term solution!
 

Colvic Watson

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I wondered the same from "shore based" RCD. I just bought a simple plug/socket RCD to put at the end of the extension reel in the boat, I assume that this would 'trip' if there was a short by - for example - dropping the heater over the side (I've done more stupid things than that!)
 
A

Anonymous

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Yes, it will trip. The way RCDs work is to compare the current in the Line with the current in the Neutral and if these differ by more than a preset amount (usually 30mA) then they trip within 25mS or so - fast enough to protect you. Usually they are made by winding the Line wire a number of turns around a toroidal transformer core and the same number of turns of Neutral round the same core, in the opposite direction. If the currents are identical then the flux in the core is zero. Even a tiny imbalance causes a significant flux in the core which is detected by a third winding, used to trip the switch. Very simple, effective and reliable.
 

TrueBlue

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I can attest to the sensitivity of modern RCDs. We live out in the sticks, where they sheep do Ba, and they cows do poo, and the 'lecky comes through the air (that means no PME). With the live of a circuit disconnected, I can get the RCD to trip if I connect the neutral to earth - usually through me... Didn't feel a thing. With a less sensitive 100mA RCD, I get a tingle.

Beats drugs

FWIW
 

VicMallows

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Sorry for delay replying, but I believe adequately answered by others. My reason for saying 'shore-based' was indeed so that the cable to the boat is also protected--dropping them in the water or touching with wet hands while power is still on are common occurences! An on-board RCD better than nothing though if impractical to fit further upstream.

Vic
 
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