RCD & GI Installation

[Murv]

One of the jobs on the new boat is to fit a galvanic isolator and a RCD.
I was thinking of this for the GI, for the RCD, can I just wire a very basic shed type unit into the output lead of the GI?
I have an external locker that is perfect for installing all of this into, it's watertight and is where the current shorepower lead plugs in so it would be convenient to fit everything in the same place.
Is the RCD circuit simply fitted inline with the 240V in?
I'm quite happy wiring 12V, but tend to avoid mains electricity unless it's very simple replacing sockets etc

 

[PotatoNavigator]

If you don't earth any part of your boat or 12V system to the 240V system (except items running on the 240V) then you don't need a GI.

 

[Tranona]

That one is expensive and you don't need those connectors if you are wiring it in permanently. The Sterling Zincsaver from Force 4 is £70 and simple to install in the 240v cabling between the inlet socket and the RCD.

 

[Norman_E]

I have one of Safeshore's standard galvanic isolators, considerably cheaper, and easy to install.

 

[VicS]

One of the jobs on the new boat is to fit a galvanic isolator and a RCD.
I was thinking of this for the GI, for the RCD, can I just wire a very basic shed type unit into the output lead of the GI?
I have an external locker that is perfect for installing all of this into, it's watertight and is where the current shorepower lead plugs in so it would be convenient to fit everything in the same place.
Is the RCD circuit simply fitted inline with the 240V in?
I'm quite happy wiring 12V, but tend to avoid mains electricity unless it's very simple replacing sockets etc

What Tranona says is true you would be paying a significant amount extra for the convenience of a "plug in" unit. Even Safeshore offer a basic unit, as Norman E points out, for £76. The Sterling one is available from chandlers eg Force 4 for £70.

What Potato Navigator says is also true. A GI is not needed if the boat's DC system, anodes etc are not bonded to the shorepower earth but for them not to be is contrary to the latest standards and recommendations.


The GI is wired into the incoming shore power earth between the inlet plug/socket and the consumer unit/RCD

I assume by "shed type unit" you refer to a "garage consumer unit" which incorporates an RCD and usually a couple of mcbs, typically one at 16amps and one at 6amps. The 6amp one can be used to connect a battery charger if you wish. Choose the best IP waterproof rating and corrosion protection you can find.
Perhaps you are just considering an RCD protected double socket?

EDIT

Rats. I have just discovered that all consumer units , garage units included , and other similar switchgear units must now have non combustible enclosures. This means that the previously available plastic enclosed units that one would naturally choose for a boat are non longer available.

 

[Murv]

Thanks all, much appreciated. Yes, sorry, I did mean a garage type unit, just something very basic so I'll find something suitable.
Thanks for the pointers on the GI, that one looked good as it was very simple, but as I'm modifying the existing wiring anyway it will be completely unnecessary so I'll go for a basic unit.

 

[SiteSurfer]

If this helps, here's my recent installation using a RCD Consumer unit (was on a special from Screwfix at the time) with the Safeshore GI plumbed in next to it.
I used Artic cable for the feed in from the shore socket and (now) out again to a locker weatherproof socket, whilst I have yet to change the twin core and earth laid in by the previous owner internally.

I have used one side for the spurs to the sockets (3) and the other will be used for the calorifier immersion circuit. (but may need uprating).

Untitled by Owen Lees, on Flickr

Following on VicS comment I found the unit here:
http://www.builderdepot.co.uk/mk-se...h3TSMZ-x-nNL3EaTQYhozdC6Cl1-qxDjzsaAhyS8P8HAQ

 

[Murv]

If this helps, here's my recent installation using a RCD Consumer unit (was on a special from Screwfix at the time) with the Safeshore GI plumbed in next to it.
I used Artic cable for the feed in from the shore socket and (now) out again to a locker weatherproof socket, whilst I have yet to change the twin core and earth laid in by the previous owner internally.

I have used one side for the spurs to the sockets (3) and the other will be used for the calorifier immersion circuit. (but may need uprating).

Untitled by Owen Lees, on Flickr

Perfect, thanks for that, that's exactly the sort of thing I'm looking at

If the marina shorepower supply is 30A, would a 32A MCB be sufficient, or do I need a large safety margin?
I'm only going to have the one MCB and RCD fitted to the single lead coming in.

 

[VicS]

If this helps, here's my recent installation using a RCD Consumer unit (was on a special from Screwfix at the time) with the Safeshore GI plumbed in next to it.
I used Artic cable for the feed in from the shore socket and (now) out again to a locker weatherproof socket, whilst I have yet to change the twin core and earth laid in by the previous owner internally.

I have used one side for the spurs to the sockets (3) and the other will be used for the calorifier immersion circuit. (but may need uprating).

Following on VicS comment I found the unit here:
http://www.builderdepot.co.uk/mk-se...h3TSMZ-x-nNL3EaTQYhozdC6Cl1-qxDjzsaAhyS8P8HAQ

The unit in the picture looks like an older type in a plastic enclosure . The one pictured in the link likewise but the description says "metal"

Perfect, thanks for that, that's exactly the sort of thing I'm looking at

If the marina shorepower supply is 30A, would a 32A MCB be sufficient, or do I need a large safety margin?
I'm only going to have the one MCB and RCD fitted to the single lead coming in.

If the consumer unit containing the MCBs can be within 0.5m of the inlet, or the cable between them enclosed in a conduit, my understanding is that an additional MCB in the incoming supply is not required.

The rating of an MCB in the incoming supply, or the combined rating of the MCBs in the consumer unit, which ever is applicable, should be no more than the safeworking current of both your shorepower lead and the pontoon supply. therefore if you have a 16amp and a 6 amp MCB that is well with the rating of a 30 amp supply.

2.5mm² "arctic" cable is a popular cable for the shorepower lead but strictly is not actually approved for the purpose, at least below +5C IIRC. HO7 , a tough rubber sheathed cable, should really be used.

 

[Murv]

Thanks for the advice all, it's much appreciated.
I've just had a chat with a guy at the club who's an electrician, he's going to give me a hand with it as the system past the shorepower is fairly complex.
Talking to him on the phone, I think I'd vastly overestimated the simplicity of it as it depends on what type of ring mains are fitted and how the thing is wired up so a bit of professional help seems a very good idea!
He's also going to order the bits in for me that he thinks are needed so I'll just get a GI as per the above.

 

[SiteSurfer]

When I refitted mine I went looking for complexity. I was put right on here

 

[VicS]

Thanks for the advice all, it's much appreciated.
I've just had a chat with a guy at the club who's an electrician, he's going to give me a hand with it as the system past the shorepower is fairly complex.
Talking to him on the phone, I think I'd vastly overestimated the simplicity of it as it depends on what type of ring mains are fitted and how the thing is wired up so a bit of professional help seems a very good idea!
He's also going to order the bits in for me that he thinks are needed so I'll just get a GI as per the above.

That sound's like an excellent plan but make sure the "guy at the club who's an electrician" is familiar with EN ISO 13297:2014, which is the standard for AC installations in small craft, and is not just going to wire it according to the IEE regulations applicable to buildings.

 

[SiteSurfer]

VicS - out of curiosity, with regard to the plastic enclosures - is it considered necessary to retrofit metal ones - or do the regs apply to new builds (so to speak) and planned refits?
Just thinking from an insurance point of view.

 

[VicS]

VicS - out of curiosity, with regard to the plastic enclosures - is it considered necessary to retrofit metal ones - or do the regs apply to new builds (so to speak) and planned refits?
Just thinking from an insurance point of view.

AFAIK there no need to replace existing plastic ones with metal ones.

It would create an insane situation if everything had to be brought up to date with every new edition of the regs. I believe the 18th edition is on its way.

 

[prv]

If the marina shorepower supply is 30A

A few places have 32A supplies for big motorboats wanting to run air-con etc, but the standard "blue socket" that most of us plug into is only 16A.

Pete

 

[Aurai]

Might be worth checking

The Amendments to wiring regulations have brought the "non-combustible" requirement for Domestic installations. You can still buy "plastic" for other locations, including commercial uses. No mention of boats that I can see, to restrict the use of plastic garage units on a boat.