Will this work / is it safe?

[Oddfellow]

A radial main loops from one socket to the next, but does not return to the main breaker. It would be incredibly unusual to see (and rather challenging) to get multiple cores into one breaker connection, though I am certain people who have no real idea might try this.

 

We're talkinig about a 20ft boat here. Put more than two individual double sockets in and you've filled 30% of the available free space anyway!

[ranworthbreeze]

As Andy says there are advantages to radial circuits and this is not purely for boats, domestic installations can and are wired for individual circuits such as fridge or freezer, outdoor sockets, immersion heater, etc.

 

On a small boat (2 or 3 sockets) I would be inclined to run them as separate circuits anyway each with its own breaker, that way if you are on shore power and are away from the boat you can turn all the breakers off other than say the battery charger or frost state controlled engine bay heaters.

 

On Ranworth Breeze when leaving the boat the only breakers left on are the 12 volt breaker for the fridge (the bilge pumps are auto) and  the battery charger/engine bay heaters.

 

Regards

Alan

[Guest]

A radial main loops from one socket to the next, but does not return to the main breaker. It would be incredibly unusual to see (and rather challenging) to get multiple cores into one breaker connection, though I am certain people who have no real idea might try this.

 

We're talkinig about a 20ft boat here. Put more than two individual double sockets in and you've filled 30% of the available free space anyway!

 

Yes, I can see your point about not needing a ring return on a boat's 240v wiring because of the 16 amp breaker, rather than the 30 amp on a house ring main.

 

I was assuming that the radial alternative would be individual spurs, because each time I've checked the 240v wiring in my boats and caravans, they've been cabled individually, as original manufacturer fitments, and one (Sealine), even used a screwed connector block kludge to multiple the cores back into the MCB connector.

 

I was also thinking generally about boat wiring and missed the fact that it was a 20 footer, yes, a full ring main would indeed be overkill !!

[littlesprite]

I know little of electrical wiring except it hurts if you get it wrong, however, I seem to remember reading somewhere that in house installations countries that use the radial system have 4mm cable as opposed to the 2.5mm ring. Britain uses the ring main as it uses less metal than the radial system which was in short supply after the war, I can't remember where I read this but if it's wrong I'm sure someone will correct me.

[ranworthbreeze]

Hi Martin,

 

You are correct re the introduction but for many houses it was into the 60's & 70's before it became common place.

 

http://en.wikipedia.org/wiki/Ring_circuit

The introduction of aluminium copper cables in the 70's (as far as I know) was a dead loss and dreadful to terminate most electricians at the time hated using it.

We electricians had to work with plenty of plain daft regulations such as the Diverity Factor used in the sizing of cables for electric cookers etc. Yes there are times when both ovens and rings not used but on average when cooking there is never enough rings and ovens.

Regards

Alan

Regards

Alan

[BroadScot]

Hi Martin,

 

You are correct re the introduction but for many houses it was into the 60's & 70's before it became common place.

 

http://en.wikipedia.org/wiki/Ring_circuit

The introduction of aluminium copper cables in the 70's (as far as I know) was a dead loss and dreadful to terminate most electricians at the time hated using it.

We electricians had to work with plenty of plain daft regulations such as the Diverity Factor used in the sizing of cables for electric cookers etc. Yes there are times when both ovens and rings not used but on average when cooking there is never enough rings and ovens.

Regards

Alan

Regards

Alan

Yes Alan,

 

Even this retired Electrician, STILL shakes his head, to this day, aye even from the days of IEE Regs 13th Edition. Some regs beggered belief, and still do!!!! 

 

Wimpey Homes were the first as far as I know to wire a complete semi-detached house about 1970/71 with ONE only ring main!. Yes One! SSHA Did also but were only about 6 or 7 sockets in a two bedroom terraced council home.

 

Still I cannot complain, thanks to them doing that it gave me lots of work in later years.

 

 

Iain.

[Guest]

.....The introduction of aluminium copper cables in the 70's (as far as I know) was a dead loss and dreadful to terminate most electricians at the time hated using it.......

 

British Telecom also went over to aluminium cored cables at that time too, as copper was getting so expensive.

 

It's much inferior tactile properties were worse for them because the solid conductor cores were so much thinner in telephone wires than 240v mains.

 

They tried it for a few years and then went back to copper, as the overall long term cost was cheaper, due to the reduction in faults.

[Oddfellow]

Yes, I can see your point about not needing a ring return on a boat's 240v wiring because of the 16 amp breaker, rather than the 30 amp on a house ring main.

 

I was assuming that the radial alternative would be individual spurs, because each time I've checked the 240v wiring in my boats and caravans, they've been cabled individually, as original manufacturer fitments, and one (Sealine), even used a screwed connector block kludge to multiple the cores back into the MCB connector.

 

I was also thinking generally about boat wiring and missed the fact that it was a 20 footer, yes, a full ring main would indeed be overkill !!

I have seen some absolutely terrible wiring on boats and have worked on a couple of unmolested Sealines too and been horrified by some things.

 

 

 

Littlesprite.....   I know little of electrical wiring except it hurts if you get it wrong,

 

Yes, it can hurt. 240v ac can kill. 12v dc can arc and start a fire. At the battery, a short across the terminals can cause horriffic burns and in the presence of sulphur gasses from charginig, can explode too. Mark at MBA Marine knows this only too well.

 

There are lots of ways of doing electrics right, but far more ways of getting it wrong and the BSS is inadequate for properly telling you whether your installations are safe as the BSS does not allow for the tester to remove any part of the boat using tools. Yet, to do any propper electrical examination (particularly 240V), you need to look at the connections to sockets and so on.  Just because you have a BSS, don't assume everything is OK.

[Guest]

I have seen some absolutely terrible wiring on boats and have worked on a couple of unmolested Sealines too and been horrified by some things........

 

Yes, it certainly surprised me.

 

My boat had a quite sophisticated electrical installation, with bespoke led control panels and electronic low voltage circuit breakers, yet the workmanship of the wiring was atrocious.

 

The 240v flex from the posh consumer unit to the sockets had bare copper showing around the cable sheath end, where the installer had simply gone round the sheath with a knife, rather than stripping back with a longitudinal slit. Luckily there was enough cable slack in the run  for me to re-terminate it properly.

 

When I did my apprenticeship in BT, the instructors would have shot anyone who did that.

[BroadScot]

With regards to Aluminium cables, some bright spark excuse the pun, decided to use it in Pyro/MICC cables, you had one go at making off a pot end, if the thread did not take, it was a length of wasted cable. Expleatives were very common place then!

 

 

Iain