Advice on shorepower?

[VicS]

VicS: Yes agree, but Boathook made no mention of a double pole RCD. Shore power is likely to have its own RCD, but unless the trip current discrimination is adequate (or time delayed), no guarantee which one trips first.

RCBO normally takes up just one width slot in the consumer unit (although one width slot RCBO’s may by now be available, I've not checked recently). So it’s a degree of extra protection if space in the consumer unit is limited. And of course makes nuisance tripping of RCD’s serving multiply circuits easier to trace if using RSBO’s instead, with one per each circuit.Thanks for your ISO document links, I’d not seen them, must read through them over Christmas.

It doesnt matter if the RCBO does trip first. A 2 pole upstream RCD will still offer protection against electrocution arising from contact with the boats neutral wiring when the polarity is reversed.

I've done a bit of reading on RCBOs and the 17th edition of the IEE regs since making my earlier post so beginning to understand the logic a bit better now.

The thing is the IEE regs apply to buildings. There may be some special considerations regarding boats, but we tend to use or adapt the installation components that are produced to comply with the IEE regs.

2 pole RCBOs exist but as far as I can see are 2 bays wide so costly on space. The 17th edition regs only require single pole RCBOs as far as I can see.

It will be interesting to see what changes there are in the next edition of ISO 13297. I believe it has been compiled and submitted for approval. It will take into account some of the current American practices required by ABYC standards etc I would think.

Some explanations of consumer unit wiring in connection with the 17 edition regs HERE Should anyone be interested.

 

[Jean]

It doesnt matter if the RCBO does trip first. A 2 pole upstream RCD will still offer protection against electrocution arising from contact with the boats neutral wiring when the polarity is reversed.

Agree, just a nuisance if it is not the local device that trips safely, and you cannot be sure of the condition of the upstream devices, but one woul hope that they are regularly tested.

Shame about BS7671 not yet covering pleasure craft, but most of it applies. There is even another set of "reg's" for big ships (got a copy somewhere). What is often overlooked by some DIY installers is the need for multi-stranded copper (claimed to reduce vibration damage risks).

 

[VicS]

Agree, just a nuisance if it is not the local device that trips safely, and you cannot be sure of the condition of the upstream devices, but one woul hope that they are regularly tested.

Shame about BS7671 not yet covering pleasure craft, but most of it applies. There is even another set of "reg's" for big ships (got a copy somewhere). What is often overlooked by some DIY installers is the need for multi-stranded copper (claimed to reduce vibration damage risks).

I'd not rely on the pontoon RCD. I think an onboard double pole one in the incoming supply is essential. It's required by ISO13297 unless certain sockets are protected individually by 10mA RCDs. Also required when the shorepower earth is not bonded to the boat's ground system.
Always possible that the pontoon RCD will trip I suppose whatever you do unless its a time delayed type. That would probably not be acceptable anyway ??

 

[nigelmercier]

I'd not rely on the pontoon RCD. I think an onboard double pole one in the incoming supply is essential...

Absolutely.

 

[Jean]

No, time delayed not acceptable on pontoon, but could have one in the marina intake room, and/or a 100mA unit perhaps, depends on supply earthing type.

Agree, an onboard douple pole RCD is advisable, BUT how many boat owners check them periodically (not just the push button test, but a real leakage current check and even that depends on the earth path quality). In a particular house, the earth path tends to be constant, but each marina adds another variable.

 

[Boathook]

Having just revisited this thread I have looked at the paper work for the RCBO's installed at home. They are single pole.
If that is the case, for use on the boat a double pole main RCD is required just in case the wiring is swapped else where. If double pole RCBO's are available I would quite happily use them with a double pole master switch just to save all the circuits going on the boat. I'm not an electrician but pick the brains of the chartered electrical engineers at work ....

 

[rosssavage]

How do you fit a GI to 12v dc??

 

[VicS]

How do you fit a GI to 12v dc??

The GI is connected in series with the incoming shorepower earth as shown in Fig 1 in the diagram below.
The "etc" of "earthing point, anodes etc" includes the DC negative (except where the dc system is fully insulated as defined in p.3.16 of ISO 10133)

 

[Jean]

Boathook, yes RCBO’s are fine used sensibly, especially if you can get quality double pole ones at the right price. The IEE reg’s (BS7671)and the other associated standard’s are not Law, just recommendations, but if you comply with them, it’s likely to be your best defence in Law should you ever have a problem. “Part P” (of the Building Reg’s) only applies to domestic installations, and I’m not aware of any Law that prevents DIY work on pleasure craft, in fact, part P does not even cover testing in domestic premises, so anyone can test their own circuits, but it tends to be the insurance companies that do any policing of this. What I’m really saying is, whatever you have installed (and personally I’d be quite happy with double pole RCBO’s in every circuit on a boat), you must have confidence in it, and the best way for that is regular functional tests (with appropriate records). No guarantee though that your “tester” electrician will get it right (I’ve seen plenty of very bad test reports even from large electrical installation companies). But if the electrician (or “chartered engineer”) has the City and Guilds 2391 Inspection and Testing certificate, you are in with a chance (there are plenty that don’t, even if they are NICEIC registered).
Incidently, "chatered engineers" are not allowed to carry out domestuc electrical installation works unless they are also part P registered.

 

[Colvic Watson]

What's the difference between a double pole and a single pole RCD? How do I know which I have in the consumer unit?

 

[Simondjuk]

1. Single pole isolates only the live. Double pole isolates both live and neutral.

2. The little schematic diagram on the front of the body of the RCD will illustrate that the device switches both L and N.

Like this....

 

[Jean]

BUT both the LINE and NEUTRAL conductors are LIVE, (even the neutral can have quite a few volts relative to earth [and can be dangerously high in some areas], depending on just where the neutral is earthed in the network, and soil conditions), so it’s important to get the terminology right. Domestic RCD’s are normally all double pole, it’s the RCBO’s (combines RCD with MCB) that are currently mostly single pole.