240v mains

[Neil Smith]

Hi all,

 

thinking about electric wiring soon, on the mains circuit the main power user will be a washing machine which is nearest the inverter so do I put in a complete ring main or just a few spurs from the w/m point.

 

Neil

[Keeping Up]

There is very little point in putting in a ring main on a boat, spurs will be fine.

[Guest]

There is very little point in putting in a ring main on a boat, spurs will be fine.

I agree. No real point in a ring main.

[Phil Ambrose]

Check that you use the correct cable,multistrand not domestic twin and earth, I believe Artic cable is a good choice but hey I'm no expert.

Phil

[alan_fincher]

Check that you use the correct cable,multistrand not domestic twin and earth, I believe Artic cable is a good choice but hey I'm no expert.

 

Yes, it is!

 

If you are going to run a full washing machine through it, including the heater, stick with the fatter 2.5mm stuff, but as has been said, there's little point in a ring main.

 

If you are feeding from a shore based source, (power point, or stand alone genny), the feed to the whole boat is likely to be that cable, or similar, anyway.

[Neil Smith]

Thanks for the help, I can get the 2.5mm multi strand stuff from my wholesaler in white, yellow, orange or blue, I think they are all the same but the white is cheaper.

so I come out of the inverter/charger to washing machine then out to the next socket etc and just terminate at the last one.

 

Neil

[by'eck]

Thanks for the help, I can get the 2.5mm multi strand stuff from my wholesaler in white, yellow, orange or blue, I think they are all the same but the white is cheaper.

so I come out of the inverter/charger to washing machine then out to the next socket etc and just terminate at the last one.

 

Neil

 

Don't forget to check that your Combi (inverter/charger) connects nominal AC output neutral to earth when (and only when) its inverter is running. Then route output to an RCD breaker before its connected to your chain of AC distribution sockets. There are safety implications if you don't ensure both these requirements are met.

[raymondh]

If you are to live aboard think of all the kit you will be using a few may be:- ie kettle,tv,sky box,hair dryer cooker, cooker hood,hoover,fridge, freezer,toaster, electric blanket, table lamp, chargers for phone/laptop.ereader etc etc

 

Unless you want leads all over put in as many sockets as you may need and for the sake of a bit of cable do a propper job as safe as required in your house and meeeting the RCD/BSS

 

Just my opinion as its harder to add later

 

Ray

[BEngo]

Thanks for the help, I can get the 2.5mm multi strand stuff from my wholesaler in white, yellow, orange or blue, I think they are all the same but the white is cheaper.

so I come out of the inverter/charger to washing machine then out to the next socket etc and just terminate at the last one.

 

Neil

 

Thanks for the help, I can get the 2.5mm multi strand stuff from my wholesaler in white, yellow, orange or blue, I think they are all the same but the white is cheaper.

so I come out of the inverter/charger to washing machine then out to the next socket etc and just terminate at the last one.

 

Neil

NO. That would be potentially, if not actually, unsafe. What you describe is half a ring and that does not have the required capacity.

 

The current carrying capacity of 2.5mm sq cable is at best about 27 A and with multi core cable, it can be as low as 17.5 A. See www.elecsa.co.uk/Technical-Library/Wiring-Regulations/Inspection-and-Testing/Current-Carrying-Capacity-of-Cables.aspx If you do as you suggest there is a strong possibility of overloading the cable. Even if your current (sic) inverter won't supply enough oomph to enable the cable to be overloaded you should still do the job properly. Someone in future might connect the boat to a generator/shoreline of sufficient capacity or put in a bigger inverter. If it's you, you won't want to re-do the 240 V wiring.

 

As noted above, you need to sort out the inverter neutral-earth link, create an earth connection between the circuit protective conductor (earth wire) and the hull and include an RCD between the inverter and the sockets. You also need a fuse/breaker panel between the RCD and the sockets for cable protection. Each socket (or double socket) outlet should really have a 15 A fuse or 16 A miniature circuit breaker or possibly 16 A RCBO's ( a combination of RCD and circuit breaker) in the fuse/breaker panel.

 

The wiring then goes:

 

Inverter- RCD- Fuse panel- multiple cables, one to each outlet.

 

Frankly, you sound as though the installation needs the assistance of a capable electrician with some understanding of the Standards set out in the Recreational Craft Directive.

 

N

[ditchcrawler]

 

NO. That would be potentially, if not actually, unsafe. What you describe is half a ring and that does not have the required capacity.

 

The current carrying capacity of 2.5mm sq cable is at best about 27 A and with multi core cable, it can be as low as 17.5 A. See www.elecsa.co.uk/Technical-Library/Wiring-Regulations/Inspection-and-Testing/Current-Carrying-Capacity-of-Cables.aspx If you do as you suggest there is a strong possibility of overloading the cable. Even if your current (sic) inverter won't supply enough oomph to enable the cable to be overloaded you should still do the job properly. Someone in future might connect the boat to a generator/shoreline of sufficient capacity or put in a bigger inverter. If it's you, you won't want to re-do the 240 V wiring.

 

As noted above, you need to sort out the inverter neutral-earth link, create an earth connection between the circuit protective conductor (earth wire) and the hull and include an RCD between the inverter and the sockets. You also need a fuse/breaker panel between the RCD and the sockets for cable protection. Each socket (or double socket) outlet should really have a 15 A fuse or 16 A miniature circuit breaker or possibly 16 A RCBO's ( a combination of RCD and circuit breaker) in the fuse/breaker panel.

 

The wiring then goes:

 

Inverter- RCD- Fuse panel- multiple cables, one to each outlet.

 

Frankly, you sound as though the installation needs the assistance of a capable electrician with some understanding of the Standards set out in the Recreational Craft Directive.

 

N

Wont he be protecting it all with a 16A breaker? less than 17.5 amps cable rating worst case.

Edited December 31, 2014 by ditchcrawler

[BEngo]

Wont he be protecting it all with a 16A breaker? less than 17.5 amps cable rating worst case.

 

The OP's original suggestion did not specifically include any breakers at all- only sockets daisy chained off the inverter, about which there are no details. I assume he either didn't realise the need to protect the cable or perhaps expected the inverter's overload protection to do that.

 

Whilst a single 16A breaker or RCBO would provide protection for the cable and daisy chained sockets, that does not leave any capability for an improved input (32 A shoreline or generator?) or deal with the capacity of the inverter to run at overload for a while (the motor-start capacity). Far better IMHO to do the job properly now, and not have to re-do later it if more capacity becomes available- the costs of the extra cable and the breakers are low (breakers are £3-54 each at Screwfix, for example) compared to the hassle of improving it later.

 

N

[Neil Smith]

A bit more info,

 

combi is 3ooo watts continuous and plan to put in about 10 sockets in various places around the boat, would it not be better to put in a ring main to avoid power loss to the furthest one, I was planning on using a small consumer unit with an rcd and 2 mcbs as used in garages, can I use a 32a mcb for the ring main or is the cable not big enough.

 

Neil

[Keeping Up]

Power loss and voltage drop will be insignificanr on a 240v system, unlike at 12v where the current is 20 times higher and every volt counts. All that matters is the current rating.

[bottle]

A bit more info,

 

combi is 3ooo watts continuous and plan to put in about 10 sockets in various places around the boat, would it not be better to put in a ring main to avoid power loss to the furthest one, I was planning on using a small consumer unit with an rcd and 2 mcbs as used in garages, can I use a 32a mcb for the ring main or is the cable not big enough.

 

Neil

 

Yes, as long as you use 2.5mm² and a ring circuit.

 

exactly as it would be wired in a house.

[Neil Smith]

So would I be better running 2 separate lines down each side and use one mcb for each side.

 

Neil

[EEng]

H07RN-F cable (only in my opinion) is far better than Arctic - some arctic is complete rubbish

[bottle]

So would I be better running 2 separate lines one down each side and use one mcb for each side.

 

Neil

 

Yes if the cable and fusing/breaker was correct as this would give you a get out clause, if one side went down the other would still work

 

You would still need 2.5mm²

 

So it is either

 

32 amp breaker and a ring circuit

 

or

 

2 * 16 amp breaker and two radial circuits

[Keeping Up]

One of the things I dislike about the usual ring arrangement is that if you fuse it for the total current and one side fails, you get no indication of a fault but everything works down the remaining side and potentially overloads it.

[BEngo]

That is one reason why the Europeans don't like the UK ring main. Another is that it's too easy to overload one because there is no limit to the number of sockets one ring can supply.

 

N

[smileypete]

If it's a typical narrowboat, just run a 2.5mm² radial from an RCD and 16A MCB, a garage consumer unit with RCD and matching MCB will do.

 

Best practice to use stranded wire not solid core, but the bare ends of fine stranded wire must be fitted with bootlace ferrules when used in screw terminals.

 

Often people use a big reel of 'blue arctic' to do the fixed wiring and make a shoreline cable, though H07RN-F rubber cable is much better for the latter.

 

Also worth having a cheap socket tester to help check the earthing status of the inverter, and test the installed wiring. An inverter connected to fixed wiring must have a functioning earth.

 

cheers, Pete.

~smpt~

Edited January 1, 2015 by smileypete

[Neil Smith]

Conflicting advice on ring or radial but I think I will go with 2 radials as my eggs will not be in one basket. Interesting about the brass ferrules on multi strand wire as when l wire a plug I just twist wires together on thick wire and double it over on thin wire.

 

Neil

[ditchcrawler]

Conflicting advice on ring or radial but I think I will go with 2 radials as my eggs will not be in one basket. Interesting about the brass ferrules on multi strand wire as when l wire a plug I just twist wires together on thick wire and double it over on thin wire.

 

Neil

Like 99% of the population.

[Guest]

 

Yes if the cable and fusing/breaker was correct as this would give you a get out clause, if one side went down the other would still work

 

You would still need 2.5mm²

 

So it is either

 

32 amp breaker and a ring circuit

 

or

 

2 * 16 amp breaker and two radial circuits

I would go fo that option. Inverters have been known to cause radio interference when a ring main is deployed.

[DHutch]

Our boat has a 32amp ring main, but it also only has a 16amp inlet.

 

I would wire a 16amp radial or two, in 2.5mm^2, which is also exactly what I have done in my garage.

 

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

 

 

Daniel

[Neil Smith]

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