Boathook
Well-Known Member
The RCBO's I have used at home are only single pole. If double pole are made I would use them on board if I was doing a rewire.
240 volt system into yacht
- Thread starter gizzy
- Start date
The RCBO's I have used at home are only single pole. If double pole are made I would use them on board if I was doing a rewire.
VicS
Well-Known Member
They're made. Google soon finds them.
Just have not yet found a suitable consumer unit with one rather than a plain old RCD
Just have not yet found a suitable consumer unit with one rather than a plain old RCD
testmonkey
Well-Known Member
single pole RCBOs are fine for home use. It is pretty unlikely to have a wiring fault at home so no need for dual pole. This is also the reason you won't typically find dual pole circuit breakers at DIY stores.
But - it is VERY DANGEROUS to use single pole breakers in marine applications as you will have a 50/50 chance to have a wiring fault when you plug in shore power using old style euro plug.
Read this:
Separate circuit breakers must never be used for disconnecting live and neutral, because if the neutral gets disconnected while the live conductor stays connected, a dangerous condition arises: the circuit will appear de-energized (appliances will not work), but wires will stay live and RCDs will not trip if someone touches the live wire (because RCDs need power to trip). This is why only common trip breakers must be used when switching of the neutral wire is needed.
http://en.wikipedia.org/wiki/Circuit_breaker
picture of dual pole breaker (which also includes RCD): http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/43444c80d4a0212ac1256f6b00395349/$file/2csc40055f0001.jpg
Basically you see that the two breakers are physically connected, when one trips it also trips the other. This makes it safe for marine applications where wiring faults can happen.
lustyd
Well-Known Member
While that may be true - if it's a completely new installation I would assume all onboard plugs will be british style and if planning to go abroad then a live/neutral indicator should be included. The unit that I have does fulfil all requirements and it perfectly safe for use within the UK - I did plenty of research on this prior to installing.
A single pole breaker will trip with the neutral disconnected as it works by detecting a difference between the live/neutral so if the current does not return then it will trip. This assumes that the live is the wire with the current in and that neutral is effectively earth (back at the substation or marina installation).
As long as there is a DP breaker further up the chain on the boat, then a reverse supply will also be tripped immediately if a neutral fault exists where neutral is live (on the continent generally).
To avoid this, an indicator can be used to show reverse supply and action taken, this can be as simple as a £2 lamp between neutral and earth wires.
This does not have to be as complicated as some are making out. Make sure you read and understand how each component works and why it's there and then make your decisions based on that. If you don't feel confident then I suggest paying a professional to install for you, but make sure they are a marine professional as shore based will probably make some mistakes based on their experience from land installations.
Cheers
Dave
testmonkey
Well-Known Member
well, I would go for a fail safe system. During that euro trip, when the SWMBO or someone else plugs in the shore cord using old style euro plug and doesn't care or understand why the lamp lights you will have danger of being electrocuted. Not necessarily a big risk, but it exists. Simply putting in a dual pole circuit breaker would make this fail safe. Also consider liability, you lend, sell or let someone else use your boat and someone gets electrocuted. Question may arise who built the unsafe shore power connection leading into the event.
Care is needed also when hiring a professional to build shore power, if the person is not familiar with marine installation requirements and the ISO standard, he/she may build it like in a household setting and thus not use dual pole trippers.
lustyd
Well-Known Member
That's effectively the same as I posted. The DP breaker was not optional, the lamp was. To make it fail safe you would need an automatic switch to change the live and neutral back to the correct way around.
VicS
Well-Known Member
You have fitted a garage consumer unit which, like those sold for shorepower intallations, has a DP RCD and SP mcbs for the individual circuits.
ISO 13297 requires that you have a DP mcb in the incoming supply. You do not have that.
northwind
Well-Known Member
As I said earlier, you want one of either of these as a good starting point:
http://www.towsure.com/product/Camping_Site_Mains_Supply_Unit_3_Outlet
"10a Twin pole circuit breaker"
Or the single socket one:
http://www.towsure.com/product/Pitch_Power_Mono_Camping_Site_Mains_Supply_Unit
The single socket one also has a reverse polarity warning light.
I've used the three way socket on my boat, and simply cut the orange cable, and added in a blue plug and socket to make the mains hookup cable. For dead simple wiring of extensions, you can then just plug in the extensions to other parts of the boat.
I'm going to add some of these sockets, as they are nice and neat:
http://www.marcleleisure.co.uk/CBE/CBE01.htm
Its worth looking at the caravan market, as the stuff they sell is often cheaper than marine.. for the same thing
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lustyd
Well-Known Member
Well if you're right then it's lucky that ISO will never check my yacht.
FWIW I don't think you are right. The DP RCD will trip both Live and Neutral if there is any residual current - this means that if there is ANY difference between the current going down the live and up the neutral (or vice versa) then both get disconnected. This device, on mine, will also trip if the total current drawn is above it's rated Amps.
The MCBs will also trip if there is a difference between Live and Neutral but on my installation this will only disconnect the live wire. Since I only use the boat within the UK this is not an issue since there will never be power in the Neutral wire, as previously stated this could easily be checked with a lamp. These MCBs also have overcurrent ratings and will trip at much lower current draw (I have tested this with an overexcited hoover and they work a treat!)
I have researched the consumer units sold as marine units and they are IDENTICAL to the one I have including the modules installed. Mine is IP65 rated with IP68 glands so passes the wetness test too.
FWIW I don't think you are right. The DP RCD will trip both Live and Neutral if there is any residual current - this means that if there is ANY difference between the current going down the live and up the neutral (or vice versa) then both get disconnected. This device, on mine, will also trip if the total current drawn is above it's rated Amps.
The MCBs will also trip if there is a difference between Live and Neutral but on my installation this will only disconnect the live wire. Since I only use the boat within the UK this is not an issue since there will never be power in the Neutral wire, as previously stated this could easily be checked with a lamp. These MCBs also have overcurrent ratings and will trip at much lower current draw (I have tested this with an overexcited hoover and they work a treat!)
I have researched the consumer units sold as marine units and they are IDENTICAL to the one I have including the modules installed. Mine is IP65 rated with IP68 glands so passes the wetness test too.
northwind
Well-Known Member
From here:
http://www.shorelineproducts.co.uk/marine_earthing.php
ISO 13297 section 4.2
The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal.
NOTE: If an RCD (whole-craft residual current device) or an isolating transformer is installed in the main supply circuit of the a.c. system (see Section 8.2), the negative ground terminal of the d.c. Systems need not be connected to the a.c. shore ground (protective conductor)
This particular part of ISO 13297 puts electrical safety totally in the hands of the RCD, but RCDs are not 100% reliable. Using an RCD alone without protective earthing is not acceptable on dry land or in a houseboat.
Note that BS 7671 is the UK version of the international standard EN 60364 electrical installation for buildings which covers the EU area. It has sections applicable to marinas and houseboats but is not applicable to small pleasure boats. However, the general philosophy of how to use mains electricity safely is consistent throughout the EU area;
a) use good quality earthing and Equipotential bonding.
b) an RCD provides additional protection, particularly in high risk areas.
c) RCDs are not allowed as a sole means of protection.
http://www.shorelineproducts.co.uk/marine_earthing.php
ISO 13297 section 4.2
The protective conductor shall be connected to the craft's d.c. negative ground (earth) as close as practicable to the battery (d.c.) negative terminal.
NOTE: If an RCD (whole-craft residual current device) or an isolating transformer is installed in the main supply circuit of the a.c. system (see Section 8.2), the negative ground terminal of the d.c. Systems need not be connected to the a.c. shore ground (protective conductor)
This particular part of ISO 13297 puts electrical safety totally in the hands of the RCD, but RCDs are not 100% reliable. Using an RCD alone without protective earthing is not acceptable on dry land or in a houseboat.
Note that BS 7671 is the UK version of the international standard EN 60364 electrical installation for buildings which covers the EU area. It has sections applicable to marinas and houseboats but is not applicable to small pleasure boats. However, the general philosophy of how to use mains electricity safely is consistent throughout the EU area;
a) use good quality earthing and Equipotential bonding.
b) an RCD provides additional protection, particularly in high risk areas.
c) RCDs are not allowed as a sole means of protection.
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lustyd
Well-Known Member
There is protective earthing in the shore cable which for most purposes is safer than earthing to the water unless you generate your own AC power on board.
VicS
Well-Known Member
You are right about the RCD tripping if there is any imbalance between the current in the live and neutral but I am afraid you are not correct in believing that it will trip on overload It is purely an RCD. The current rating is it is not a tripping current it is its max safe current rating (40A)
The two mcbs on the individual circuits are SP overcurrent trips ( one at 6A and one at 16A) but they are only overcurrent trips, not RCDs, they will not trip on imbalance between live and neutral.
What you have is fine, but you are lacking the DP MCB over current protection in the incoming supply called for by section 7.2 of the ISO.
Talbot
Well-Known Member
Lots of good things already said about RCDs and circuit breakers. However one area that gets missed / and has not been mentioned on any of the other posts, is that the wiring needs to be multi/stranded rather than single. The single strand wiring normally required in house wiring tends to work harden then eventually break on board a boat.
VicS
Well-Known Member
Yes we saw it first time around but we are taking about fixed installations. In particular about the suitability of various consumer units and the application of ISO13297.
The Kampa units from Towsure do however appear to satisfy the requirement for a DPMCB and an RCD ( hopefully that is DP )
Your quotation of section 4.2 from the ISO is out of context. It deals with the bonding of the shorepower earth to the DC negative/ vessels internal earthing system.
Scarboroughsloop
Well-Known Member
I am also looking for a basic way of adding shorepower and am going to fit one of these:
http://www.power-store.com/view-item.asp?itemid=245&id=45&
As a bit of an electrical numpty it looks good to me, but does it fit the bill?
http://www.power-store.com/view-item.asp?itemid=245&id=45&
As a bit of an electrical numpty it looks good to me, but does it fit the bill?
lustyd
Well-Known Member
That is a very expensive solution indeed, and looks to me as though it's basically the same as a garage unit and a charger. I bought all my electrical bits and a multistage charger for around £240. Having said that it's probably nice and simple to install.
lustyd
Well-Known Member
Ignore this post I was wrong - I missed the bit that said "double-pole circuit-breaker
device intended to interrupt both the neutral and live conductors in a circuit simultaneously when a designated
current is exceeded for a predetermined time"
OK I've now read the blasted ISO document. It states that on Unpolarised systems a DP overcurrent protection is required on both Live and Neutral. On polarised systems, only on the Live.
A Polarised system is one where all wiring uses live as live and neutral as neutral. This is what we in the UK have and so is sufficient for most yachts. Even when abroad, if the live and neutral are reversed, as long as you have means to detect and correct this you still have a polarised system and therefore do not require DP overcurrent protection.
I think that Vic is reading a little too much into the wording which is actually not there.
Vic is quite right that extra safety can be added by OPTIONALLY adding overcurrent protection to the whole boat but the standard does not seem to require this.
device intended to interrupt both the neutral and live conductors in a circuit simultaneously when a designated
current is exceeded for a predetermined time"
OK I've now read the blasted ISO document. It states that on Unpolarised systems a DP overcurrent protection is required on both Live and Neutral. On polarised systems, only on the Live.
A Polarised system is one where all wiring uses live as live and neutral as neutral. This is what we in the UK have and so is sufficient for most yachts. Even when abroad, if the live and neutral are reversed, as long as you have means to detect and correct this you still have a polarised system and therefore do not require DP overcurrent protection.
I think that Vic is reading a little too much into the wording which is actually not there.
Does not say that overcurrent is required here and it is not implied by being in the overcurrent protection section.
Does say that overcurrent devices are required on branch circuits.
Vic is quite right that extra safety can be added by OPTIONALLY adding overcurrent protection to the whole boat but the standard does not seem to require this.
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lustyd
Well-Known Member
Here we go an RCBO which will replace the RCD in the consumer units and make it comply with ISO
Then you just need a label maker to comply with the other requirements...
Then you just need a label maker to comply with the other requirements...
VicS
Well-Known Member
Completely revised reply
As said it is an expensive item, in fact it is very expensive, but it is a neat solution to providing the basis for a fairly simple (2 circuits ) shorepower system combined with a good battery charger.
It has the necessary RCD, aka RCCB, and a 2 Pole main circuit breaker.
Each circuit has a single pole MCB .. all that is required with a polarised system
Just the job and meets all the requirements as far as I can see.
Protect the wiring as specified in ISO 13297 7.2.2 if there is more than 0.5m between the input receptacle and the Dolphin unit
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