240v Installation Info and Advice Please

[muzbaz]

No problem with the long run to the batteries, just position the inverter unit close to them, and run the 240v output 3 core flex to wherever you want to intercept the shorepower feed between the exterior inlet socket and the consumer unit.

 

You're quite right in understanding that the low voltage inverter feed cables need to be as short as practical, because the high current at 12v would demand even thicker cables if the run was 25ft.

 

The mains output flex at 240v has no such length constraints though, and can easily handle that distance.

 

It's just a question of mounting the new additional blue shorepower plugs and sockets anywhere convenient.

 

 

:

 

Thanks Strowager for the detailed images, one small concern:

 

If running the 240v output from the inverter over a distance to hook into the system with a 3 way as MBA described, 'break before make' type switch (before the consumer) then is that supply from the inverter supposed to be fused or have it's own breaker? or is that dealt with by the inverters fuse or on/off control?

 

Freedom great points regarding normal domestic TV's etc, I have got away with going straight to battery DC supply in the past, but fully appreciate that if the TV doesn't have a way of regulating the current it can be terminal or at least damaging to the circuitry, as you say th voltage can vary so much, an old CRT type set would take a pounding but today's panels are so different so I really would consider something like MJT gave a link to. 

[Oddfellow]

Thanks Strowager for the detailed images, one small concern:

 

If running the 240v output from the inverter over a distance to hook into the system with a 3 way as MBA described, 'break before make' type switch (before the consumer) then is that supply from the inverter supposed to be fused or have it's own breaker? or is that dealt with by the inverters fuse or on/off control?

 

 

 

No fusing is needed before the consumer unit.

 

All power supplies run to the Make-before-break selector swicth in the first instance and from there, one supply out to the consumer unit. Don't forget, there will be a 13amp plug and socket on the inverter end anyway.

[Guest]

......If running the 240v output from the inverter over a distance to hook into the system with a 3 way as MBA described, 'break before make' type switch (before the consumer) then is that supply from the inverter supposed to be fused or have it's own breaker? or is that dealt with by the inverters fuse or on/off control?......

 

 

As you correctly surmise, and Freedom has replied, most inverters are designed with one or two standard 13 amp outlet sockets, so the lead from that to the changeover switch will be via a fused 13 amp plug.

 

Likewise, the other input lead from the shorepower lead is protected by the shorepower post's circuit breaker.

[muzbaz]

Ah,,Of course,,,, I overlooked the fused plug. 

Another question comes to mind,,, Should the 240v supply be installed as a 'ring' returning to the consumer as you would have in your home, or would/could it be terminated at the last socket as if creating a spur or essentially a long extension lead?

 

I appreciate your time and knowledge guys 

Thanks

[Oddfellow]

You can install a ring if you like, but unless you are going to be using high power items for long periods, it's pretty unnecessary, AND, the shorepower line will only be 16amps anyway which is why you don't need to use 2.5mm cable around the boat.

 

A radial circuit is all that's necessary. Try to make sure that all connections are in socket boxes as you should in any installation.

[Guest]

 

..... Should the 240v supply be installed as a 'ring' returning to the consumer as you would have in your home, or would/could it be terminated at the last socket as if creating a spur or essentially a long extension lead......

 

 

To expand on what Freedom has already replied with, you could connect the 13 amp sockets either radially or as a ring , whichever is the most convenient for the cable runs.

 

You need to remember the purpose of ring mains in houses.  They save the amount of cable run, and also the physical congestion of cables back at the consumer unit. 

 

The backing fuse in each domestic house ring main is 30 amps, because although the domestic 2.5 t&e cable is about 18 amps, the current is effectively supplied from both directions within the ring, so the cable current rating is effectively 36 amps, so it could safely carry the maximum that it could get from the 30 amp backing fuse.

 

The maximum current from a standard shorepower connection though, as has been said,  is only 16 amps anyway, so a 30 amp fuse or mcb for the ring would be superfluous.

 

The bottom line is that you can connect the 240v sockets back to the consumer unit whichever way is the most convenient for the cable runs.

 

Contrary to what some people might think, you can safely put as many 240v sockets in as you like, near anywhere where mains equipment may be used. It's then neater to just connect them together in ring main fashion, just linking the first and last back to a single 15 amp mcb or fuse. Much neater than trying to terminate several cables on to one screw terminal.

 

Remembering of course that instead of 18amp 2.5mm t&e solid flat cable, only the equivalent three core stranded mains flex cable should be used in caravans or boats, because of the vibration.

[Oddfellow]

Expanding on what Strowager said, never connect more than one circuit to a MCB. That is to say, if you have five sockets, don't run five cables back to the MCB.

 

A radial circuit should run from the consumer unit and into a socket, then out of that socket to another and so on.

 

If you so choose, you can run a cable back from the final socket to the MCB to create a ring main, but it's probably entirely unnecessary as discussed.

[littlesprite]

I won't advice on boats but can help explain the difference between Radial and ring installations.

A ring main supplies current from both cables, a radial obviously only one, this means a radial circuit requires larger diameter cable.

UK ring main uses 2.5mm cable, a radial circuit would require 4mm cable.

 

The UK opted for ring mains after the war to reduce the amount of copper needed in 2.5mm cable over 4mm cable, I believe the USA is predominantly 4mm radial. 

[muzbaz]

Freedom and Strowager that's as clear as gin! (although I prefer vodka  )   but then littlespirit throws a spanner in the works! Humph,,, I was going to go with 2.5mm Arctic cable to satisfy the possible BSS requirements once they decide to incorporate shore power into the requirements for a cert, getting it wrong could mean having to refit.

 

Running a return to make it a ring is the simplest solution I think, conduit large enough to carry a double thickness of wire at 2.5 mm solves the problem for the sake of 12-15 m of cable and is just another 3 connections to make good and tidy.

 

As always

Thank you

[mjt]

The UK opted for ring mains after the war to reduce the amount of copper needed in 2.5mm cable over 4mm cable, I believe the USA is predominantly 4mm radial. 

 

Since the USA is 110V the current would be about double for a given wattage so they'd need heavier cable anyway.

 

[MBA Marine]

I always use 2.5 arctic not because I need to but if the boat leaves the broads (or in a few places on the broads) and ends up in big marinas they can be on a 20a supply and its simple to change out the MCB to be able to harness the larger supply not so easy to change the cables throughout.

 

If all your sockets are down one side than radial is a simple solution, if your going down one side and back up the other the completing the ring would make sense.  

[littlesprite]

mjt, your right 110v would require thicker cable than 240v, the point I was trying to make is that radial also requires thicker cable than a ring main as you only use one cable to feed every socket.

As a matter of interest the USA do use 240v on high consumption items (cookers, emersion) they use the 110v on plugs as it's supposed to reduce the risk of death.

[mjt]

Hi Martin,

 

I take your point. I was simply observing that using 4mm radial at 110V would really be roughly equivalent to using 2.5mm at 230V radial.

 

I didn't realise the USA used 240V for high-wattage wired-in equipment. Incidentally I've always understood that their 110V supply is centre-tapped at the substation thus giving 55V between each conductor and earth, this being much safer in the event of a shock.

[mbird]

I installed the 240v in Tranquil Breeze as a ring, since I needed sockets both sides, and it seemed neater to simply connect the final socket back to complete the ring.

[littlesprite]

Hi mjt,

I think you probably know that 110v is standard site power in the UK as well again for safety, this will also use two 55v cables so that cutting through a single cable will have a much lower risk of fatality.