ISO10133 small craft wiring exceptions

[mikeb123]

Hi all

I'm designing the electrical system for a new boat, and I have a question on wiring (again - there are few I see, although I can't find this one in the archives)

Specifically, regarding minimum size for wiring the USCG code has the following exception

This section does not apply to communications systems; electronic navigation equipment; electronic circuits having a current flow of less than one ampere; conductors which are totally inside an equipment housing; resistance conductors that control circuit amperage; high voltage secondary conductors and terminations that are in ignition systems; pigtails of less than seven inches of exposed length and cranking motor conductors.

but I can't find a similar exception for ISO-10133, the rest-of-world equivalent. Anyone know if there is one, and can they point me to it? If not then even an NMEA-0183 to USB connector or a VGA cable would have to be wired with 0.75mm2 strands....

 

[mikeb123]

No replies so I'll follow myself up with more detail.

First, I think the important clause here is 7.1 in that specification:

7.1 Electrical distribution shall use insulated stranded-copper conductors....

So this only applies to "electrical distribution", which is a very wooly term. For example, NMEA2000 micro cabling can carry up to 4 amps and uses AWG22 wire - about 0.35mm2, well below the minimum 0.75mm2. So is every NMEA2000 cable over 200mm long disallowed? (Incidentally, this question has been discussed relating to the USCG code as well).

The reason I ask all this is not hair splitting - I don't want to wire the boat up only to be told by the surveyor it's not to up code and therefore uninsurable. So if anyone can clarify this I'd appreciate it.

 

[missinginaction]

Hi mike and welcome.....

First a disclaimer. I'm not an EE or a marine electrician. But I am wiring a 27 ft dual station cruiser and I'm pretty thorough as far as doing my homework.

I've used a couple of resources to guide me as I designed my system.

1. A Book. A really good one. The link is below. It does have a section that covers European standards for cable sizing. A wonderful resource.

http://www.amazon.com/Boatowners-Me...&keywords=nigel+calder+boat+owners+electrical

I've also developed great respect for the people at Blue Sea Systems in Bellingham, Washington USA. I've purchased a number of their products (panels/ACR's/terminals/bus bars/etc.) and have been impressed with the quality of materials and workmanship. They have a number of calculators and technical references on their web site that might be helpful.

http://www.bluesea.com/

I've found that aside from battery cables, inverter cables and DC branch circuit feeder cables I've used mostly AWG 16 cable and occasionally AWG 12 cable. The 16 gauge cable was sometimes overkill in terms of voltage drop but my understanding is that 16 gauge should be the minimum size cable used for most all marine wiring due to it's greater strength and durability. I used a bit of AWG 18 cable (sheathed) for signal cable from oil pressure gauges, temperature, etc.

Perhaps this will help. The lack of responses might have to do with the differences between US and UK standards. I notice there isn't a lot of action on the electrical section. Maybe a lot of guys don't like to tackle electrical.

MIA

 

[mikeb123]

Thanks missinginaction - Calder's book is by my bedside and I'm currently re-reading the relevant chapter nightly It's a piece of work alright, and when my shiny new hulls turn up in a few months it will be put into proper service.

For the individual power carrying cables I completely agree on AWG16 (or 1.5mm2 which is our equivalent). What I'm not clear on is the data cables - i.e. those carrying a digital signal rather than powering a device. Here the current is minimal, typically a few tens of mA, and the voltage drop is irrelevant as you just need to differentiate between 0 and 1.

You guys in the US get an exception for these cables, but do we? I think so, but it's one of those things you want to be sure on before you put in a few hundred metres of wiring. I think it might be time to make friends with a marine electrical supplier.

 

[missinginaction]

I can't say weather you get an exception in Great Britain as I don't have that information.

I would say that everything I've ever read from the US Coast Guard or ABYC and even the ISO info that you posted the link to, every standard was designed to prevent fires. With that in mind it would seem reasonable that your standards in the UK would be designed to prevent fires as well.

I know that here we can use 18 gauge wire to carry signals from fuel senders and the like as long as they are sheathed. That is my understanding. I can see the rational behind the sheathing as unsheathed AWG 18 is pretty spindly stuff, easily damaged. The wiring to my transducers looks like AWG 22 but it's in a protective sheath. Even with a 1 amp load which is way more than a data cable would ever carry, according to my calculator you could run an AWG 18 cable (0.82 square mm) out 90 feet (and back) which would be roughly 27 meters with less than 10% voltage drop. I'll wager that you're over thinking this as thick wiring for the data cables you mention doesn't pass the reasonableness test.

Could you take a look at a reasonably new boat that has systems similar to yours and see what the manufacturer used? Just to put your mind at ease?

Good Luck with your boat!

MIA

 

[Mark Cat]

ISO 10133:2000

Chapter 7

Section 7.6

For Electrical Distribution:

Min single conductor size over 200mm in length 1mm^2 (16 AWG).

Min conductors in multi-conductor cable with outer sheath, extending out individually less than 800mm, 0.75 mm^2 (approx 18 AWG).

Min single conductor in panelbaord 0.75 mm^2 (18 AWG).

Very similar to ABYC.

Regards,

Mark Cat

 

[T0x1c]

It is common for eg Simrad or Raymarine materials, which are CE approved, to find 28 to 20 AWG for signal cables.

See for instance Notice for Simrad AP16 Autopilot: "Signal cables should be 0.5mm2 (AWG20) twisted pairs".

I don't think that signal cable is to be considered as continuous current conductor under ISO 10133. Furthermore under CE, your only obligation is the 95/CE directive and addendum; following material manufacturer's recommendations is also an approved way for CE compliance.