Battery Charger Installation

[Morris]

When setting up a battery charger for occasional use to be powered by shore power on an otherwise 12V only boat what degree of permanence do you feel is advisable/ would you feel comfortable with? 

1) shore lead in through window/pigeon box, 16 to 13a socket converter, charger attached to batteries with croc clips. 

2)as per 1 but battery charger has 16v plug, is attached to batteries and fused

3) as per 2 but with shore power inlet fixed to outside of boat

4) as per 3 but with gi & hull earth bonding

5) as per 4 but with consumer unit. 

6) other 

[Paul C]

I’d not be relying on shoreline to trip in a fault situation, so I’d have proper earthing and RCD on the boat. And proper connections to the battery for BSS req

[blackrose]

Yes, think about it this way. How comfortable would you be putting a loose mains extension lead into a small steel box which is floating in a bath full of water without any consumer unit, breakers or earth bonding point inside the steel box? Then how about putting your bare hands into the box and operating some mains switches and small appliances. If you don't think that's a good idea why would you want to do the same thing on a larger scale?

 

You already know the correct answer to your question. If you're going to install mains on a boat then do it safely and properly.

Edited October 20, 2023 by blackrose

[Jen-in-Wellies]

23 minutes ago, Morris said:

shore lead in through window/pigeon box, 16 to 13a socket converter, charger attached to batteries with croc clips.

Nope. Any sharp edge on the window, or pigeon box can wear through the cable. Croc clips are a BSS fail.

25 minutes ago, Morris said:

2)as per 1 but battery charger has 16v plug, is attached to batteries and fused

Sharp edges again.

24 minutes ago, Morris said:

3) as per 2 but with shore power inlet fixed to outside of boat

Getting better, can't rely on shore bollard earth leakage detector, as per @Paul C.

27 minutes ago, Morris said:

4) as per 3 but with gi & hull earth bonding

The GI means you now have no RCD protection on board. Various earth faults on board can now definitely kill you.

27 minutes ago, Morris said:

5) as per 4 but with consumer unit. 

👍. Do it properly, or not at all. Mains can kill. Not just you, but some one falling in to the water nearby.

[nicknorman]

11 minutes ago, Jen-in-Wellies said:

 

The GI means you now have no RCD protection on board. Various earth faults on board can now definitely kill you.

 

Don’t think that bit is right. Why does the insertion of a GI prevent an upstream RCD from working?

[Jen-in-Wellies]

3 minutes ago, nicknorman said:

Don’t think that bit is right. Why does the insertion of a GI prevent an upstream RCD from working?

You are correct. Scrub that bit.

[jonathanA]

As always you need to assess the level of risk you are happy with (including risk to others). 

 

if you suggesting that whilst say visiting the boat on sunday afternoon you would plug in an extension lead and put the batteries on charge with a portable charger (croc clips) for a couple of hours whilst you are there that is a vastly different situation to leaving it like that for days/weeks unattended... 

 

if you have access to a permanent shoreline then you'd be silly not to set yourself up to use it safely and do a proper install that you can use to keep your batteries charged through Winter and maybe even some frost protection via 'greenhouse' type tube heaters or oil filled electric radiators. 

 

Its easy for me to say its not expensive (to me ) to do it properly, i don't know your circumstances/level of ability, but the costs aren't that great.  A 'garage' consumer unit can be had for less than 40 quid, GI is probably the most expensive bit, one with a status indicator going to be around a £100 and then a 16A inlet - less than a tenner, a bit of 'arctic blue' flex few quid and a bit of 6MM earth cable for the hull bond  a quid or two for a few metres,  then maybe a 13A socket and/or a fused spur to wire the charger (assuming its a proper multistage charger) into.  

 

all assuming steel boat rather than GRP, although I'm thinking the only real difference there is the hull bond. 

 

ETA - obviously this is 'high level' and not meant as complete instructions and if your not comfortable then you should seek advice/someone competent to do it.  Lots of guidance from the good folk here too. 

Edited October 20, 2023 by jonathanA
see ETA.

[cuthound]

35 minutes ago, Jen-in-Wellies said:

Nope. Any sharp edge on the window, or pigeon box can wear through the cable. Croc clips are a BSS fail.

Sharp edges again.

Getting better, can't rely on shore bollard earth leakage detector, as per @Paul C.

The GI means you now have no RCD protection on board. Various earth faults on board can now definitely kill you.

👍. Do it properly, or not at all. Mains can kill. Not just you, but some one falling in to the water nearby.

 

The RCD trips en there is a 30mA imbalance between the live and neutral currents. It does not rely on an earth connection.

[Morris]

Thanks for the replies, fwiw I wasn't trying to get away with an unsafe installation, I'm actually pretty darn risk averse!

I had been reading past threads on the topic and thought that some knowledgeable folks had suggested that something other than option 5 was acceptable, but I probably misunderstood. 

8 minutes ago, jonathanA said:

whilst say visiting the boat on sunday afternoon you would plug in an extension lead and put the batteries on charge with a portable charger (croc clips) for a couple of hours

 

This is what I was envisaging in this (at present completely hypothetical) situation, my thinking being that the charger would only be used very occasionally (once a week/fortnight) and plugged in for maybe 2-3 hours at a time. 

48 minutes ago, cuthound said:

 

The RCD trips en there is a 30mA imbalance between the live and neutral currents. It does not rely on an earth connection.

 

I'm interested in this, because it seems to be the opposite of what is written on this page

http://www.tb-training.co.uk/MarineE11.html#MAINS Electricity 

ie, 'without a working earth system the RCD cannot work'. 

[Tracy D'arth]

1 hour ago, Morris said:

 

 

I'm interested in this, because it seems to be the opposite of what is written on this page

http://www.tb-training.co.uk/MarineE11.html#MAINS Electricity 

ie, 'without a working earth system the RCD cannot work'. 

It would have applied to the older ELCB type protection but not an RCD or RCBO protection.

[cuthound]

1 hour ago, Morris said:

I'm interested in this, because it seems to be the opposite of what is written on this page

http://www.tb-training.co.uk/MarineE11.html#MAINS Electricity 

ie, 'without a working earth system the RCD cannot work'. 

 

This gives a detailed description of how an RCD works.

 

https://www.consumerunitworld.co.uk/what-is-an-rcd-and-how-does-it-work-337-c.asp#:~:text=The Residual Current Device%2C or,a given number of circuits.

 

As I said it operates when there is an imbalance between live and neutral currents of more than 30mA. The difference between the two currents being the current that is leaking to earth.

 

It does NOT need a working earth connection, Indeed most mains operated outdoor tools such as lawn mowers are double insulated and this have no connection to earth.

 

Tony is probably thinking of the predecessor to the RCD, the ELCB (earth leakage circuit breaker) which did require an earth connection.

 

 

Edited October 20, 2023 by cuthound
To add a missing link

[Alan de Enfield]

1 hour ago, Morris said:

I had been reading past threads on the topic and thought that some knowledgeable folks had suggested that something other than option 5 was acceptable, but I probably misunderstood. 

 

There is absolutely no requirements in the BSS to meet any "standards" for your 230v AC wiring - Although potentially dangerous, the BSS will still grant a 'pass' if your wire is poked thru a window and the sheath is chafed all the way thru.

 

They will say to you "we advise you do it properly but there is no requirement to do so".

[Morris]

12 minutes ago, cuthound said:

 

This gives a detailed description of how an RCD works.

 

https://www.consumerunitworld.co.uk/what-is-an-rcd-and-how-does-it-work-337-c.asp#:~:text=The Residual Current Device%2C or,a given number of circuits.

 

As I said it operates when there is an imbalance between live and neutral currents of more than 30mA. The difference between the two currents being the current that is leaking to earth.

 

It does NOT need a working earth connection, Indeed most mains operated outdoor tools such as lawn mowers are double insulated and this have no connection to earth.

 

Tony is probably thinking of the predecessor to the RCD, the ELCB (earth leakage circuit breaker) which did require an earth connection.

 

 

 

Thank you for the link and additional explanation, I appreciate it.

[Chewbacka]

4 hours ago, cuthound said:

 

The RCD trips en there is a 30mA imbalance between the live and neutral currents. It does not rely on an earth connection.

So please explain how you can have a 30mA or greater imbalance between live and neutral if the ‘imbalance’ current isn’t flowing via the earth.  Where does the ‘missing’ current go?

[Tracy D'arth]

2 minutes ago, Chewbacka said:

So please explain how you can have a 30mA or greater imbalance between live and neutral if the ‘imbalance’ current isn’t flowing via the earth.  Where does the ‘missing’ current go?

To a body in contact with the ground?

[Chewbacka]

1 minute ago, Tracy D'arth said:

To a body in contact with the ground?

Exactly, it goes via the earth.

[cuthound]

18 minutes ago, Chewbacka said:

So please explain how you can have a 30mA or greater imbalance between live and neutral if the ‘imbalance’ current isn’t flowing via the earth.  Where does the ‘missing’ current go?

 

It can be going to earth through you (electric shock) or leaking to earth via some other path such as damp connections. 

 

 

13 minutes ago, Chewbacka said:

Exactly, it goes via the earth.

 

But not through a designated earth connection. The original question suggested that 'without a working earth system the RCD cannot work'. 

Edited October 20, 2023 by cuthound
To add spaces between merged posts

[blackrose]

While the RCD or GFCI may or may not work without an earth connection depending on the type (and some do work in different ways), surely that's largely irrelevant. The point of the earth path is to ensure that if the hull becomes live anyone touching the hull does not become a path to earth. 

[Tony Brooks]

3 hours ago, Alan de Enfield said:

 

There is absolutely no requirements in the BSS to meet any "standards" for your 230v AC wiring - Although potentially dangerous, the BSS will still grant a 'pass' if your wire is poked thru a window and the sheath is chafed all the way thru.

 

They will say to you "we advise you do it properly but there is no requirement to do so".

 

No Tony is thinking of how a cut into a conductor onto the hull can provide a reliable alternative path if the hull is not earthed. In my view the water is not a reliable path so you could end you with a live hull yet not enough imbalance between line and neutral to trip the RCD. Better safe than sorry. A live hull can kill if the path to earth is via you.

[BEngo]

The point of the earth path is to ensure that if the hull  ( which must be connected to the earth path) becomes live the current flowing as a consequence is sufficient to operate the protective device ( blow the fuse/trip the breaker).  Circuit breaker devices protect the circuit equipment, not people.

 

If you were to have an earth path, but no protective device, or an earth path with high resistance and a protective device  then with the hull live it is quite possible that someone touching the hull and standing on the bank, say,  would get an electric shock.  This is also why really long extension  leads are a Bad Thing.  The resistance in the earth conductor can become large enough to prevent the circuit breaker or fuse. from operating.

 

RCD's are the thing needed to protect people.

 

N

[Alan de Enfield]

9 minutes ago, Tony Brooks said:

 

No Tony is thinking of how a cut into a conductor onto the hull can provide a reliable alternative path if the hull is not earthed. In my view the water is not a reliable path so you could end you with a live hull yet not enough imbalance between line and neutral to trip the RCD. Better safe than sorry. A live hull can kill if the path to earth is via you.

 

My post was not regarding the 'earth path' I was responding to suggestions that he 'must' wire it up properly and the BSS was mentioned.

 

When it comes to the BSS and 230v AC there are no 'requirements' just 'advisories'

[jonathanA]

I think that is slighlty muddled thinking Tony.  If the imbalance isn't enough to trip the RCD, in theory you might feel a tingle or even a receive a shock, but it should not be enough to kill you (thats why its set at 30mA for RCDs on final circuits).  whenever I've tripped RCDs, usually by touching the neutral on a circuit with the (single pole) MCB off , I've never felt a thing, i'm not sure that would be the case if i was swimming or stood in a canal/river at the time...  which is also why the RCD has to trip more quickly if the imbalance is larger. 

 

your supposed to use 2 pole RCBOs on CUs supplying caravans or boats (caravan site and marina electrical regs ) or an RCD which isolates ALL phases AND neutral usually this is done by having an RCD (shock hazard) and then one or more MCBS (over current protection). So a typical RCBO would not meet this requirement as they are often single pole and do not disconnect the neutral.   And to Bengo's point leads from the 'hook up' point on caravan parks/marinas are supposed to be a maximum of 25M IIRC. 

Edited October 20, 2023 by jonathanA
add shock/over current in brackets and changed MCB to RCBO. (getting myself confused)

[blackrose]

13 minutes ago, BEngo said:

RCD's are the thing needed to protect people.

 

 

Surely both the RCD and the earth path may both be needed to protect people? It doesn't have to be a choice.

23 minutes ago, Tony Brooks said:

In my view the water is not a reliable path 

 

Is it any less reliable than any other path? An unpainted baseplate seems like a pretty good path to me.

[Tacet]

4 hours ago, Alan de Enfield said:

 

There is absolutely no requirements in the BSS to meet any "standards" for your 230v AC wiring - Although potentially dangerous, the BSS will still grant a 'pass' if your wire is poked thru a window and the sheath is chafed all the way thru.

 

They will say to you "we advise you do it properly but there is no requirement to do so".

Whilst they are not that onerous, there are several BSS requirements for AC.  For example 3.3.1 requires all cables to be supported in a safe position.

[Sea Dog]

2 minutes ago, Tacet said:

Whilst they are not that onerous, there are several BSS requirements for AC.  For example 3.3.1 requires all cables to be supported in a safe position.

Yeah, but....

Surely the extension lead, charger and croc clips can all go in the hedge for the duration of the inspection, along with the junk out of the gas locker, the generator and the petrol cans, etc?