240v mains

[smileypete]

Yes mind made up 2 radials with 2 x 16amp mcbs, do I just clip the cable to battens or run in conduit, and also the 12v conduit or just in roof void and tunnel void.

 

Neil

 

From another topic 'is that allowed under BSS?'. No-one seems to know for sure (including the BSS inspector bods), it just needs someone to ask BSS head office.

 

Personally I'd just run both radials through a single 16A MCB.

 

Bootlace crimps, put on with a decent ratchet crimper are good but not essential.

 

Maybe, but you might as well wire a narrowboat with twin 'n earth.

 

Ratchet crimper isn't essential for bootlace ferrules, ferrule pliers can be had quite cheaply, normal pliers will do in a pinch. Ebay and CPC are a good source for the ferrules.

 

cheers, Pete.

~smpt~

Edited January 2, 2015 by smileypete

[ditchcrawler]

Yes mind made up 2 radials with 2 x 16amp mcbs, do I just clip the cable to battens or run in conduit, and also the 12v conduit or just in roof void and tunnel void.

 

Neil

Not sure quite what you mean but it is debatable if you can run the 240 volt cable in with the 12/24 volt cables. I say debatable because some people claim thatthe outer sheath of a three core mains flex segregates it from the 12/24 volt system.

[Guest]

 

From another topic 'is that allowed under BSS?'. No-one seems to know for sure (including the BSS inspector bods), it just needs someone to ask BSS head office.

 

Personally I'd just run both radials through a single 16A MCB.

 

 

Maybe, but you might as well wire a narrowboat with twin 'n earth.

 

Ratchet crimper isn't essential for bootlace ferrules, ferrule pliers can be had quite cheaply, normal pliers will do in a pinch. Ebay and CPC are a good source for the ferrules.

 

cheers, Pete.

~smpt~

A pair of end cutters/pincers used gently do a reasonable job (blades along the ferrule not across.) Forms a figure of eight on the cross section. The proper tool is always best of course.

Edited January 2, 2015 by Guest

[NMEA]

Not sure quite what you mean but it is debatable if you can run the 240 volt cable in with the 12/24 volt cables. I say debatable because some people claim thatthe outer sheath of a three core mains flex segregates it from the 12/24 volt system.

No debate really, unless properly seperated or one is in a conduit then you may not run low voltage AC and extra low voltage DC cables together, the exception is if the AC cable has an outer braid capable of carrying a minimum of the cable conductors current, RCD, ISO & NMEA0400 standards are very clear on that.

Edited January 3, 2015 by NMEA

[EEng]

Just to be clear from a technical point of view

 

Its not just 32 amps for a ring (2 x 2.5mm2) or 16Amps for a radial (1 x 2.5mm2)

 

It depends on the calculations done for the circuit and depending on the factors involved you could be using a 20 amp breaker for an RFC (ring final circuit) or a 10 or even a 6 amp breaker for a radial circuit

[bottle]

Yes and perhaps it was remiss of us to not state that we were discussing, what the general public know as a 'ring main' ie. a circuit with 13 amp square pin sockets.

 

A ring circuit can be of any size as you say ie, lighting, that would have a lower fuse/breaker rating.

[Keeping Up]

Yes but under what circumstances on a boat would you need to de-rate a 2 x2.5mm ring circuit to 20A, or 2.5mm radial circuit to 6A ?

[John V]

No debate really, unless properly seperated or one is in a conduit then you may not run low voltage AC and extra low voltage DC cables together, the exception is if the AC cable has an outer braid capable of carrying a minimum of the cable conductors current, RCD, ISO & NMEA0400 standards are very clear on that.

 

There is also a cable (BICC Multiplus) that is constructed within an aluminium tube that is then clad it white xlpe insulation. Visually it is indistinguishable from 2.5mm white 3 core flex. This CAN be run together with ELV as it is classed as being within a conduit. However it generally means major warfare when dealing with surveyors or, in my case consultants, who have never heard of it. (incidentally it can also be run touching polystyrene without degrading although temperature de-rating has to be considered)

There are often alternatives to standard systems that are perfectly safe and legal but you will get very fed up with having to prove it time after time.

[davey b]

No debate really, unless properly seperated or one is in a conduit then you may not run low voltage AC and extra low voltage DC cables together, the exception is if the AC cable has an outer braid capable of carrying a minimum of the cable conductors current, RCD, ISO & NMEA0400 standards are very clear on that.

How far is the minimum separation?

 

Are the RCD standards available on line like BSS? If they all agree, the ISO & NMEA standards are available at a significant cost... A set was well over a £100 when I last looked on behalf of the company - and not a full set either...

[NMEA]

Unless on a ladder with a physical seperator then the seperation is 100mm.

 

ISO, NMEA & RCD documents are copyright and need to be bought, I know that they are all pretty keen to protect that copyright. £74 + VAT ,for BSI members (non members £174) is only the cost for one ISO document and you need at least two, one for low voltage AC and another for extra low voltage DC, it would be nice if they were combined into one document. NMEA0400 standard is $375 for non members (few people in UK are members)

[davey b]

Thank you... very prompt.

 

'Ladder with a physical separation' - would a ELV DC conduit suffice (or do you mean an actual ladder... with rungs?)

[ditchcrawler]

Is this a new boat or are you doing a refit?

[Arthur Brown]

ON a boat a ring or radial circuit properly calculated can be current limited by a breaker (or HRC Link) at currents not usually installed in a house. You don't need an upstairs ring or a cooker point or a shower circuit, probably because the generator or shore line wouldn't support them anyway.

 

Remember also that Arctic cable doesn't comply with the current wiring regs for use at 240v even though it does comply with 110CTE systems.

While almost everyone uses blue arctic for the lead to the bollard that cable should be H07 RNF though HO5RNF is sometimes easier to source but less abrasion resistant. The blue arctic is suitable for use as trunking cable for 240v.

 

For the few of us on 32 or 63A supplies, especially any with three phase five wire please take specialist advice, That would be a LOT for a narrow boat but not much for a seagoing vessel.

 

Yes I know one venue in London that supplies the DJ with a 125/3 which is just a little OTT.

[davey b]

Is this a new boat or are you doing a refit?

 

Is that for me or Neil (the OP)? If its for me, its a mod/refit/update

[Tom Richmond]

Can I confirm if I understand all the above correctly?

 

Low voltage AC = 240v AC also known as "mains".

 

Extra low voltage DC = 12v DC also known as "battery".

 

Cables carrying each of these types of power must be separated from each other, either by conduit, or a gap of 100mm.

 

My previous understanding (from available BSS docs) was that the only instance that cables required conduit was when running alongside a gas line, and then that a three core 240vAC line could class it's outer covering as a conduit.

[alan_fincher]

Can I confirm if I understand all the above correctly?

 

Low voltage AC = 240v AC also known as "mains".

 

Extra low voltage DC = 12v DC also known as "battery".

 

Cables carrying each of these types of power must be separated from each other, either by conduit, or a gap of 100mm.

 

My previous understanding (from available BSS docs) was that the only instance that cables required conduit was when running alongside a gas line, and then that a three core 240vAC line could class it's outer covering as a conduit.

 

I think there is probably a big difference between what is necessary to pass a BSS, and what is required for full compliance with RCD, and other standards. The BSS is currently generally far less demanding, I believe, even if all the other stuff may be good practice.

 

If you have an older boat, and only need to satisfy BSS requirements, then I think what you have put in your final paragraph is correct.

 

Personally I would say even then the minimum "standard" you should set yourself if not putting the 240 volt in a conduit, is that you only use cable with an outer sheath throughout, that is clearly identifiable as being the 240V, and cannot possibly be confused as 12 volt. The idea of having wires running through that do not have an outer sheath, where there could be any ambiguity about which are 12 volts and which are 240 volts fills me with horror.

 

That said, guess who has just bought a boat with very dodgy electrics, and where I have already established that some of the Arctic type cable is being used for 12 volts!

[ditchcrawler]

 

Is that for me or Neil (the OP)? If its for me, its a mod/refit/update

OP

[Helgashumans]

I"d just like to point out that a 3 kva inverter isn't going to put out more than 16 amps continuously anyway. If you have two radial circuits each protected with a 16 amp mcb, you could draw more than 16 amps from the inverter and be reliant on the inverter's overload protection. Also, if you're hooked up to a standard 16 amp shoreline supply and exceed a total of 16 amps, it will be the onshore box that trips out, meaning you have to go ashore to reset it. Surely better to have one 16 amp breaker with all sockets running from a radial circuit connected to it with appropriately sized cable.

[Tom Richmond]

 

I think there is probably a big difference between what is necessary to pass a BSS, and what is required for full compliance with RCD, and other standards. The BSS is currently generally far less demanding, I believe, even if all the other stuff may be good practice.

 

If you have an older boat, and only need to satisfy BSS requirements, then I think what you have put in your final paragraph is correct.

 

Personally I would say even then the minimum "standard" you should set yourself if not putting the 240 volt in a conduit, is that you only use cable with an outer sheath throughout, that is clearly identifiable as being the 240V, and cannot possibly be confused as 12 volt. The idea of having wires running through that do not have an outer sheath, where there could be any ambiguity about which are 12 volts and which are 240 volts fills me with horror.

 

That said, guess who has just bought a boat with very dodgy electrics, and where I have already established that some of the Arctic type cable is being used for 12 volts!

 

 

Thanks.

 

All as per my existing knowledge (and the wiring on my boat!)

 

I just like to have an idea of best practice so I can implicate it if doing anything new...

 

Currently all 240v has outer sheath in white, and is the only white cable on the boat.

 

When I first got the boat there was an instance of two pieces of the same orange three core cable being used side by side, one with 240v running through it, and the other with the blue and brown being used for 12v +ve and -ve. Where the "spare" yellow and green cable emerged from the stripped end of the sheath, it had been wrapped around a screw as a form of locating the cable to the wall. Needless to say this part of the installation has now been removed!

[nicknorman]

I"d just like to point out that a 3 kva inverter isn't going to put out more than 16 amps continuously anyway. If you have two radial circuits each protected with a 16 amp mcb, you could draw more than 16 amps from the inverter and be reliant on the inverter's overload protection. Also, if you're hooked up to a standard 16 amp shoreline supply and exceed a total of 16 amps, it will be the onshore box that trips out, meaning you have to go ashore to reset it. Surely better to have one 16 amp breaker with all sockets running from a radial circuit connected to it with appropriately sized cable.

However if said device is a 3kw combi, it can be used in "power assist" mode to get around 29A, 16A from shore power merged with 13A from the inverter.

[by'eck]

I"d just like to point out that a 3 kva inverter isn't going to put out more than 16 amps continuously anyway. If you have two radial circuits each protected with a 16 amp mcb, you could draw more than 16 amps from the inverter and be reliant on the inverter's overload protection. Also, if you're hooked up to a standard 16 amp shoreline supply and exceed a total of 16 amps, it will be the onshore box that trips out, meaning you have to go ashore to reset it. Surely better to have one 16 amp breaker with all sockets running from a radial circuit connected to it with appropriately sized cable.

 

I wouldn't rely too much on inverter overload protection. Better to limit current draw from it via suitable MCB or better still an RCBO since you need an RCD anyway. A DC fuse rated at no more than max current draw +20% will help as well.

 

When I accidentally drew too much from a 16 amp shore supply, not surprisingly the pedestal breaker tripped. This left my 3.2kW Sterling Combi's inverter making a brave attempt to supply 4kW+. Due I suspect to a well engineered DC supply the battery volts didn't drop as quickly as might have been expected so the unit kept running although probably for less than a minute, until the 500 amp DC fuse blew. Another example of a fuse saving the equipment BTW.

 

I have now fitted a 16 amp RCBO on the inverter/pass through AC outlet to replace the previous RCCD.