Ac system requirements

[WotEver]

Well for starters your shoreline connection should not have a plug on it at the boat end.

???

 

OP was talking about the boat wiring. He said

Shore line connection plug fed into an RCD (residual current device) within 0.5 meters form the plug,

This is entirely correct.

 

Why do you think it is not?

 

Tony

 

Edited to make the quote a quote

Edited February 29, 2016 by WotEver

[WotEver]

The ISOs are available FoC here (which is great because they are really expensive to buy.

 

http://www.manchester.gov.uk/info/200062/libraries/110/online_reference_library/4

Brilliant, thanks

[by'eck]

Before embarking on installation of my AC system, if anyone could share any information on the following I would appreciate it.

 

According to the RCD (recreational craft directive) is the following AC system acceptable? (I shall start form shoreline connection to AC outlets)

 

Shore line connection plug fed into an RCD (residual current device) within 0.5 meters form the plug, the RCD shall be housed in a waterproof box next to the plug (a garage box). This RCD shall feed into two single pole MCBs, one connected to the diesel immersion heater, and the other connected to the inverter.

Out of the inverter I propose to feed another RCD, housed within the electrical cupboard which shall feed two other single pole MCBs, a 10A MCB for a ring circuit of ac sockets (12 sockets, which I know is a large amount for one ring, but with 2.5mm cable and a smaller MCB this will reduce loading the sockets with the full whack of the 3KW inverter), and the other 12A MCB for a washing machine.

 

My main question is... Does the galvanic isolator need to be connected at both RCDS or would connecting it to the first RCD ground the inverter through the galvanic isolator? Or do both RCDs and Inverter require grounding through the galvanic isolator.

 

I will also be connecting the inverter to the batteries but that shall be for another day.

 

Thanks,

 

Will

 

Hopefully this diagram of my setup helps and incorporates a few of the concepts suggested above, as well as covering most of your queries.

 

 

The first RCD is not strictly necessary although its incorporated as an RCBO to provide current limiting as well, as the shore side pedestal should protect up to the Combi's inverter. Note that second charger and immersion heater are fed directly before the inverter maintained supply from Combi.

[nicknorman]

Why have a 25A RCBO at the inlet? Surely if you are going to have an over current trip it might as well match the current limit of the connector and cable ie 16A?

[nicknorman]

I thought we had established that a 3kW inverter was unlikely event be centre tapped though?

Yes this is true. I had something in the back of my mind about a need for double pole breakers but as you say, not relevant to this thread.

 

Edit: Oops, it is relevant, breakers on supply circuits (ie shore power, inverter) must be double pole.

Edited March 1, 2016 by nicknorman

[smileypete]

Yes, use flex but I wouldn't use any ferrules. 1. I don't believe that the sockets are specifically "designed" for solid wires. 2. Using ferrules immediately negates one of the main reasons for using flex, the compression of the flexible wire means that the screws in the sockets don't come loose under vibration of the boat.

 

(I'm sure people will disagree with this but my experience has proved that I am right on this)

 

They're designed for solid and stranded wire, but not fine stranded wire. A look at the terminal screws will reveal they likely have rounded ends, when fine stranded wire is terminated under them it tends to splay apart and loosen.

 

cheers, Pete.

~smpt~

[by'eck]

Why have a 25A RCBO at the inlet? Surely if you are going to have an over current trip it might as well match the current limit of the connector and cable ie 16A?

 

It would seem wise yes but you already have one on the pedestal if its a 16 amp feed. Anyway was looking at your skinny shore cable only yesterday

[nicknorman]

It would seem wise yes but you already have one on the pedestal if its a 16 amp feed. Anyway was looking at your skinny shore cable only yesterday

 

I suppose it is easier to reset a breaker on the boat than on a shore bollard. A 25A breaker is never going to trip so why have it?

 

Hmmm, can't remember what size cable I used for that short lead, but it hasn't melted yet and there's been a few times it's been operating at 16A. Probably being outside in the breeze allows a degree of under-rating. Especially the bits dangling in the cut!

 

Anyway, 1.5mm^2 is adequately rated for 2 core sheathed at 16A in free air and I think that is what it is.

Edited February 29, 2016 by nicknorman

[David Mack]

???

 

OP was talking about the boat wiring. He said This is entirely correct.

 

Why do you think it is not?

 

Tony

 

Edited to make the quote a quote

The connection of the shoreline to the boat should be made using a socketon the shoreline and an appliance inlet on the boat as below. If a plug is used on the shoreline with a socket attached to the boat, then live pins could be exposed, if the lead is connected at the shore end but disconnected at the boat.

 

Shoreline socket:

 

Appliance inlet:

[WotEver]

The connection of the shoreline to the boat should be made using a socketon the shoreline...

Absolutely. And what does a socket connect to? A panel mounted plug as you showed:

Appliance inlet:

Call it an "appliance inlet" if you like but it's still a plug - it has pins.

 

So OP's description of "Shore line connection plug fed into an RCD..." was entirely correct.

 

Tony

Edited March 1, 2016 by WotEver

[Robbo]

Thanks for the all the information so far.

I am do plan to have an electrician install all the equipment, but as fitting out on the water in London, they are like gold dust to get a hold of for work. Therefore I aim to purchase the required equipment so I can have it all ready for a professional to install.

I plan to have a victron multiplus charger inverter 3KW.

As CC the 10A MCB was an idea to discourage high AC power use, and an idea i shall put to bed.

I shall put together a diagram to aid my description.

 

Thanks again for all the information,

 

Will

I believe the Victron has two outlets, one is live for shore power only. Both will need RCDs. If it has it will be better rather than splitting before the Victron as the Victron won't overload the shore power where splitting the supply to the water heater before hand could. If it doesn't have two outputs, you can use the alarm relay output to control another relay to turn on/off The AC outputs.

 

Important, don't do a N/E bond, the combi does this for you when not on shore power. If you do it yourself you could make the hull live if the shore power / cable is incorrectly wired.

Edited March 1, 2016 by Robbo

[by'eck]

I suppose it is easier to reset a breaker on the boat than on a shore bollard. A 25A breaker is never going to trip so why have it?

 

Hmmm, can't remember what size cable I used for that short lead, but it hasn't melted yet and there's been a few times it's been operating at 16A. Probably being outside in the breeze allows a degree of under-rating. Especially the bits dangling in the cut!

 

Anyway, 1.5mm^2 is adequately rated for 2 core sheathed at 16A in free air and I think that is what it is.

 

Guess I was thinking along the lines of 30 amp feeds which were popular at marina's I used to frequent - I do carry an adaptor for such.

 

Regarding shore cables, I remember arriving in the USA and meeting up with our Florida neighbours at the first marina we visited. His comment on seeing my shore cable was geez I wouldn't run my toothbrush on that

[WotEver]

Regarding shore cables, I remember arriving in the USA and meeting up with our Florida neighbours at the first marina we visited. His comment on seeing my shore cable was geez I wouldn't run my toothbrush on that

Don't forget that he's used to half the mains voltage than we have - hence twice the current for a given load.

 

Tony

[by'eck]

Don't forget that he's used to half the mains voltage than we have - hence twice the current for a given load.

 

Tony

 

I hadn't - typically US boats have twin 115 volt feeds via humungous cables from a centre tapped 230 volt 50 amp pedestal socket.

[boater123]

I have put together a single line diagram for simplicity and to ascertain if I have all the correct components, and wiring routes.

I have included the grounding line of each piece of equipment, but not shown the grounding wiring of each RCD/MCB again for simplicity. Is there any route that I have missed?

as for second AC output from the inverter, this is some blurb form the inverter spec, ' The second output is live only when AC is available on one of the inputs of the MultiPlus.'

As robbo suggested there would need to be an RCD on both inverter outputs, so I therefore we have 3RCDS in the system. Is this excessive or deemed safe?

I understand RCBOs could be used to save space, but have shown RCD/MCB combinations here.

 

any thoughts on this would be appreciated.

 

Thanks,

 

Will

[John V]

On the subject of double pole as opposed to single pole mcb's, if I was wiring up a boat today with the availability and cheapness of double pole mcbs, that is the way I would go................it might not be necessary but it makes finding which circuit has a neutral earth fault a doddle, much better than having to go through the distribution panel disconnecting neutrals

[boater123]

The RCD standards say '7.2.1 double pole circuit breakers shall be installed in conductors to all supply circuits'. Sounds like it makes life easier

[Paul C]

It is bad practice to have 2x RCDs connected in series - and I know the shoreline bollard probably has one too, but its allowable because basically there's one on the boat and you'd be daft not to have one and rely on the shoreline alone. 2x MCBs in series is fine because in your case they are protecting different things - the first one in the shoreline - inverter is protecting the whole installation; the others are protecting their individual circuits.

Here's my suggestion for a modification:

 

EDIT Scrub that! I just realised you'll need the extra RCDs because without them, it leaves the mains unprotected if you're on inverter only. Its an anomoly with a combi - its both an inverter and a battery charger. If its an inverter it generates electricity so you want the RCD & MCBs on its output; if its a battery charger then it needs to be protected so it needs RCD & MCB on its input! And since the same wires are used when in "pass through" there's no way round the situation....so you're stuck with having 2x sets of RCDs etc in series unfortunately.

[boater123]

Thanks Paul,

 

If the shoreline were to be disconnected and I was running the inverter off the batteries, would I still not need that second RCD for running the washing machine and socket ring?

[Paul C]

Thanks Paul,

 

If the shoreline were to be disconnected and I was running the inverter off the batteries, would I still not need that second RCD for running the washing machine and socket ring?

 

Yes - I'm not sure if you saw my edit, after I looked more closely....

[WotEver]

I have put together a single line diagram for simplicity...

any thoughts on this would be appreciated.

 

Looks good, Will. Just ensure that the earth connection within the garage consumer unit cannot make any connection to the hull.

 

Otherwise I can't see any obvious way of improving on it.

 

Cheers,

Tony

[nicknorman]

You don't need the RCD on the water heater circuit. That is only active when on shore power and you already have a shore power RCD. As mentioned, there is not point and it is possibly a bad idea to have 2 RCDs in series.

 

On the subject of having 2 MCBs for the ring main and washing machine, why bother? Why not just have one MCB for the lot, rated at 16A. Then you can use wiring appropriate for 16A safe in the knowledge that you can never exceed 16A for the whole circuit. More MCBs just complicates things!

 

Well that is with one caveat, depends on whether you are going to use the Victron in power assist mode. This would allow you to have more than 16A on at once with the inverter supplementing the shore power using battery power. We don't use this function and have just one 16A breaker but I suppose if you want to use it then you need breakers with a total of more than 16A to be able to use it.

 

When on shore power we prefer it to be that or nothing and have the combi in charger - only mode, that way if the shore power fails we know about it, rather than the batteries suddenly having to supply all the AC load via the inverter with the consequence of flat batteries.

 

Last point, have you considered having a shore inlet at each end of the boat? I rather wish we had because, depending on which way the boat is moored at our marina, sometimes I have to run a long cable along the roof to the bollard, it drapes over the well deck and is a bit of a pain. If you do decide to have 2 inlets you need switchery (either manual or automatic) to ensure that when shore power is plugged in at one end, the other end isn't live.

Edited March 1, 2016 by nicknorman

[nicknorman]

The RCD standards say '7.2.1 double pole circuit breakers shall be installed in conductors to all supply circuits'. Sounds like it makes life easier

 

Yes it's a bit confusing but note it says "supply circuits" so you can, say, have a double pole breaker for the shore inlet and inverter output, and then use single pole breakers in a consumer unit to supply various services. However I think it is much easier just to use double pole breakers all round.

 

I've edited my earlier post where I said double pole was only needed for non-polarised circuits, which was wrong for supply circuits.

Edited March 1, 2016 by nicknorman

[cuthound]

 

Last point, have you considered having a shore inlet at each end of the boat? I rather wish we had because, depending on which way the boat is moored at our marina, sometimes I have to run a long cable along the roof to the bollard, it drapes over the well deck and is a bit of a pain. If you do decide to have 2 inlets you need switchery (either manual or automatic) to ensure that when shore power is plugged in at one end, the other end isn't live.

I have this facility on DQ and very useful it is too.

 

The manual "switching" is achieved by the leads from each mains inlet terminating in a socket on a flying lead. The flying lead to be used is simply plugged into the single "master" mains inlet plug, all of which are located in a cupboard which also contains the combi and the galvanic isolator. Simple, safe and effective as only one flying lead can be connected at a time.

[nicknorman]

I have this facility on DQ and very useful it is too.

 

The manual "switching" is achieved by the leads from each mains inlet terminating in a socket on a flying lead. The flying lead to be used is simply plugged into the single "master" mains inlet plug, all of which are located in a cupboard which also contains the combi and the galvanic isolator. Simple, safe and effective as only one flying lead can be connected at a time.

 

Hmmm, hopefully this is not a 13A plug and socket arrangement? 16A into 13A doesn't go! Of course if you are using a 16A plug and 2 16A sockets then fine!

 

We don't have 2 sockets but if we did I think I'd go for an automatic switchover (eg masterswitch) - a little pricy but not really, in the context of a new boat.

 

Do you have 2 GIs / ITs or just one, after the sockets (or maybe none!)?