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12 v socket wiring - double checking


RickS

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11 minutes ago, ditchcrawler said:

I knew a boater who used all 13 amp sockets so that he could also use his extension leads for 12 or 240 outlets. All his 12 volt appliances were connected positive to neutral and negative to earth in case they got put in the wrong socket. He also had a valve an his water tank vent and a hose adaptor on his filler so at the moorings he could pressurise the system and not need a pump. Some people with active mined are always coming up with "good ideas".

Would he also have had the useful "Male to Male" extension to connect external shore power into a convenient 13A socket onboard?

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47 minutes ago, 1st ade said:

Would he also have had the useful "Male to Male" extension to connect external shore power into a convenient 13A socket onboard?

That is quite possible but as he died a few years back or very old age I can't ask him. 

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1 hour ago, 1st ade said:

Would he also have had the useful "Male to Male" extension to connect external shore power into a convenient 13A socket onboard?

You talking about 13a house plug on each end of an extension cable? Why would you use something like that when you have a shore line socket on boat. Better to just use a 13a plug to shoreline plug short extension and plug your normal shoreline cable into that.

Edited by PD1964
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47 minutes ago, PD1964 said:

You talking about 13a house plug on each end of an extension cable? Why would you use something like that when you have a shore line socket on boat. Better to just use a 13a plug to shoreline plug short extension and plug your normal shoreline cable into that.

We know what's better, we also know what some people do. Not all boaters have a shore supply plug on their boats. and how many times have we seen it suggested to connect a genny to a house during a power cut.

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22 minutes ago, ditchcrawler said:

We know what's better, we also know what some people do. Not all boaters have a shore supply plug on their boats. and how many times have we seen it suggested to connect a genny to a house during a power cut.

I very nearly got bitten by a supposed professionals installation of such a piece of kit. We were fitting out some server racks to provide resilience (using a different make of server and a different operating system) to try and make sure essential IT services kept going from December 31st 1999 to January 1st 2000. There were insufficient electrical feeds in the data hall, the "local engineer" tapped his nose and said "leave it to me". We (perhaps unwisely) did...

 

Came time do dismantle the kit (having had no trouble at all from Y2K) we couldn't find how to turn the rack off!- never mind, pull all the power cables and start removing servers. At some point we found an IEC "male" connector with a cable vanishing down a hole in the floor - it popped in a different rack across the aisle - also with a male IEC on it. And plugged into a distribution board which was live...

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As an addendum to this topic, I traced the wire feeding the twin 13A sockets and found the other end was attached to a 13A plug, plugged into a normal square pin 4-way extension lead tucked away at the back of a cupboard! Also plugged into this extension were leads supplying a light underneath a wall unit and a light in a kitchen cupboard / pantry. Needless to say, these were all unplugged and the extension lead disconnected.

I must admit to being slightly gobsmacked by this. The wire supplying the extension lead disappears into the wall. What I would like to do is extend the cable that was supplying the extension lead as it is not really long enough to be useful.

The cable that was attached to the twin 13A socket has two multi-strand cables within that are about 2.5-3 mm diameter, as is the one I want to lengthen.

Given that I want to run a 65W laptop charger in one 12 volt socket and USBs in the other, is that cable suitable please?

The only other option as far as I can see is stripping the cable back to the battery and inserting new - which I'd rather not do unless I have to - hence my question.

Thanks

Edited by RickS
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1 hour ago, RickS said:

As an addendum to this topic, I traced the wire feeding the twin 13A sockets and found the other end was attached to a 13A plug, plugged into a normal square pin 4-way extension lead tucked away at the back of a cupboard! Also plugged into this extension were leads supplying a light underneath a wall unit and a light in a kitchen cupboard / pantry. Needless to say, these were all unplugged and the extension lead disconnected.

I must admit to being slightly gobsmacked by this. The wire supplying the extension lead disappears into the wall. What I would like to do is extend the cable that was supplying the extension lead as it is not really long enough to be useful.

The cable that was attached to the twin 13A socket has two multi-strand cables within that are about 2.5-3 mm diameter, as is the one I want to lengthen.

Given that I want to run a 65W laptop charger in one 12 volt socket and USBs in the other, is that cable suitable please?

The only other option as far as I can see is stripping the cable back to the battery and inserting new - which I'd rather not do unless I have to - hence my question.

Thanks

 

You need to work out the total cable length (both ways - so if it is say 10 metres from the battery the total is 20 metres) and the total current (the 65 watts for example will be 6.5 amps for example) that will be on the circuit (all plugs / appliances added together.

 

The deciding factor on cable size will be volt drop NOT curremt carrying capacity.

 

Once you know the above information come back and we will work out the volt drop and the best size of cable.

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1 hour ago, jamie preston said:

personally, i would forget what is installed and start again. it's obviously been done by an amateur with an enthusiastic mind! it's quite likely that there are other issues that you can't see that will also need to be rectified.

best to start over!

Probably right, I'm just not sure how I would get new cables through without taking the wall linings down - and that's not happening at this time of year!

39 minutes ago, Alan de Enfield said:

 

You need to work out the total cable length (both ways - so if it is say 10 metres from the battery the total is 20 metres) and the total current (the 65 watts for example will be 6.5 amps for example) that will be on the circuit (all plugs / appliances added together.

 

The deciding factor on cable size will be volt drop NOT curremt carrying capacity.

 

Once you know the above information come back and we will work out the volt drop and the best size of cable.

Will do, thanks Alan

28 minutes ago, PD1964 said:

All these extension cable and plugs you mention are all 12v supply using 240v 13A type sockets/plugs/extensions?

  Have you a proper 12v wiring system with an appropriate and marked control panel or is all your 12v system like this?

  

Seem to be. There is a breaker box but nothing labelled, except the fridge, which I did by trial and error. So yes, there is a proper 12 volt wiring system that seems to have been rewired with 13 A plugs / sockets. Crazy

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10 minutes ago, RickS said:

So yes, there is a proper 12 volt wiring system that seems to have been rewired with 13 A plugs / sockets. Crazy

 

I'm afraid I do not agree.

A 12 volt system wired via  multi-ganged extension leads, thenselves plugged into a double socket and using 230v 13a 'mains sockets' as 12v outlets is as far a way from a 'proper 12v circuit as anything could be. It is probably the most 'unproper' thing I have ever heard of.

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28 minutes ago, RickS said:

 There is a breaker box but nothing labelled, except the fridge, which I did by trial and error. So yes, there is a proper 12 volt wiring system that seems to have been rewired with 13 A plugs / sockets. Crazy

Fridges normally have their own dedicated 12v supply.

  Maybe the 13a type sockets were a thought by the previous owner who couldn’t be bothered to run proper wiring ring hence the extension block and plug system.

  I would trace back all the 13a socket 12v stuff and rip out and start again as mentioned above with the correct gauge cabling to prevent voltage drop, work out exactly what 12v sockets(cig/usb type) you need and only fit those, running back to the control panel. It may be easier then you think but protect them with conduit and you’ll have peace of mind which is the main thing.

  

  

Edited by PD1964
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21 minutes ago, Alan de Enfield said:

 

I'm afraid I do not agree.

A 12 volt system wired via  multi-ganged extension leads, thenselves plugged into a double socket and using 230v 13a 'mains sockets' as 12v outlets is as far a way from a 'proper 12v circuit as anything could be. It is probably the most 'unproper' thing I have ever heard of.

Totally agree, sounds like the previous owner couldn’t be bothered to do it properly. 13a sockets, plugs and extension blocks, totally daft.

 Rip out, re wire using proper sockets, fit a good 12v labelled control panel, job done, peace of mind.

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10 hours ago, RickS said:

Probably right, I'm just not sure how I would get new cables through without taking the wall linings down - and that's not happening at this time of year!

 

Personally I would ever run wring behind the wall panels because it is difficult to get at for additions or repair. I don't know your boat but many will have the possibility of running cables, behind a suitable moulding, where the ceiling joins the cabin sides or where the hull side lining meets the floor. In many cases there is  a full length timber plank under the gunwales where additional cables can be run in plastic clip top trunking.

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10 hours ago, RickS said:

Probably right, I'm just not sure how I would get new cables through without taking the wall linings down - and that's not happening at this time of year!

Disconnect (where possible) the 240v end fittings - by judicious gentle "tugging" establish if you might be able to use the existing wire to pull the right stuff through...

 

Failing that, replace the 240v fittings with unambiguous 12v equivalents even where out of sight - it'll be a lot better than what you have now. Upgrade the cable run later when it's warmer

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11 hours ago, RickS said:

Probably right, I'm just not sure how I would get new cables through without taking the wall linings down - and that's not happening at this time of year!

 

It sounds as if this may be an 'elderly' boat - what insulation does it have ?

 

If it is polystyrene insulation then you should not let your PVC cable get in contact with it. There is a chemical reaction between PVC and Polystyrene which means that the PVC insuation becomes embrittled and can fall off leaving bare copper condustors which can short out and, in the best case blow fuses, in the worse case start a fire. Polystyrene is extremely flammable. You can make napalm using petrol and polystyrene and we all know how nasty Napalm is,

 

Run the cable thru a conduit behind the lining, or use a self adhesive truking under the gunwale - it comes with a removable lid so it is easy to add / remove cables at a later date.

 

It is not expensive, comes in various sizes and makes a tidy job (and is much easier than taking down you walls).

 

Tower uPVC White Self-Adhesive Mini Trunking 25mm x 16mm x 2m | Mini Trunking Lengths | Screwfix.com

 

64026_P&$prodImageMedium$

Edited by Alan de Enfield
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12 hours ago, Alan de Enfield said:

 

I'm afraid I do not agree.

A 12 volt system wired via  multi-ganged extension leads, thenselves plugged into a double socket and using 230v 13a 'mains sockets' as 12v outlets is as far a way from a 'proper 12v circuit as anything could be. It is probably the most 'unproper' thing I have ever heard of.

Poor choice of words on my part. I meant separate 12 volt supply with it's own fuse box - don't know if that would be described as 'proper'. What has been done to it after it has left the fuse box is a bit of a mess.

The run of cable from the batteries to the location of the new sockets is 12 metres - so 24 metres in total. I tried to allow for the bends and twists so 12 m is as near as makes no matter. As I mentioned before, one 12 volt socket to run a 65W laptop charger, the other one to run a twin USB supply - one at 2.1 amps, the other at 1 amp - although if both are used they both run at 1 amp.

Does this help with ascertaining the cable size or is more info needed?

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2 hours ago, Tony Brooks said:

 

Personally I would ever run wring behind the wall panels because it is difficult to get at for additions or repair. I don't know your boat but many will have the possibility of running cables, behind a suitable moulding, where the ceiling joins the cabin sides or where the hull side lining meets the floor. In many cases there is  a full length timber plank under the gunwales where additional cables can be run in plastic clip top trunking.

You're right Tony, I should have explained myself better. There are cables running under the gunwales - amongst other things - so that would present few problems. It's when the odd cable runs into the wall lining i have no idea whether it stays there or reappears under the gunwales.

The insulation is polystyrene so I appreciate the possible issue with PVC, ideally None of the cable would be anywhere near the insulation - although there are a few wall lights in the saloon which do have their cables running behind the lining, and presumably the ceiling lights must do as well

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1 minute ago, RickS said:

You're right Tony, I should have explained myself better. There are cables running under the gunwales - amongst other things - so that would present few problems. It's when the odd cable runs into the wall lining i have no idea whether it stays there or reappears under the gunwales.

The insulation is polystyrene so I appreciate the possible issue with PVC, ideally None of the cable would be anywhere near the insulation - although there are a few wall lights in the saloon which do have their cables running behind the lining, and presumably the ceiling lights must do as well

 

Again, personally and without seeing the boat, I would drill upwards through that under gunwale plank close to the cabin lining and immediately below the socket. The probe about with a long rod or dowel. I think you could easily make a hole up to the socket. Then push some tunking or sleeving past the insulation to accept the cables. Use a fish-wire if necessary. A serviceable fish-wire can be had for a few £ as a tape type drain cleaner.

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2 hours ago, Alan de Enfield said:

 

It sounds as if this may be an 'elderly' boat - what insulation does it have ?

 

If it is polystyrene insulation then you should not let your PVC cable get in contact with it. There is a chemical reaction between PVC and Polystyrene which means that the PVC insuation becomes embrittled and can fall off leaving bare copper condustors which can short out and, in the best case blow fuses, in the worse case start a fire. Polystyrene is extremely flammable. You can make napalm using petrol and polystyrene and we all know how nasty Napalm is,

 

Run the cable thru a conduit behind the lining, or use a self adhesive truking under the gunwale - it comes with a removable lid so it is easy to add / remove cables at a later date.

 

It is not expensive, comes in various sizes and makes a tidy job (and is much easier than taking down you walls).

 

Tower uPVC White Self-Adhesive Mini Trunking 25mm x 16mm x 2m | Mini Trunking Lengths | Screwfix.com

 

64026_P&$prodImageMedium$

Thanks Alan. Lightbulb just flicked on! If the cabling is behind the wall linings, I can just disconnect and leave it there, resupplying via under-gunwale trunking.  Doh!

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20 minutes ago, RickS said:

The run of cable from the batteries to the location of the new sockets is 12 metres - so 24 metres in total. I tried to allow for the bends and twists so 12 m is as near as makes no matter. As I mentioned before, one 12 volt socket to run a 65W laptop charger, the other one to run a twin USB supply - one at 2.1 amps, the other at 1 amp - although if both are used they both run at 1 amp.

Does this help with ascertaining the cable size or is more info needed?

 

Ok. Volt drop (what voltage comes out of the cable compared to what goes in) is affected by Voltage, current drawn and cable copper cross sectional area (size)

The 'normal acceptable volt drop is a maximum of 4% and nearer 2% is the target.

 

Taking 12m (one way) at 12 volts.

You will be using around 7.5 amps, lets call it 10 amps just in case you plug another phone onto charge somewhere in the circuit.

 

The wiring already existing is quite likely to be 1.5mm2 or at best 2.5mm2 so what would be the volt drop on these :

 

1.5mm2 will give 3.04 volt drop (25.4%)

2.5mm2 will give 1.80 volt drop (15.2%)

 

You need to go to 10mm2 cable which will give you a 0.44 volt drop (3.64%) just below the maximum 4%

 

Hope this helps.

 

70 AMP 10mm2 84/0.4 Stranded Thin Wall Single Core Copper Cable Wire 12V 24V | eBay

 

£1.95 per metre.

 

So you see - the current rating of the cable is irellevant (70 amps to supply 10 amps) - It is volt drop that determines cable size on a long boat (NOT a Longboat - Vikings didn't go much on 'leccy)

 

You may find that it will not fit into your terminals so 'work will be needed' to fit it.

 

 

Edited by Alan de Enfield
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11 minutes ago, Alan de Enfield said:

 

Ok. Volt drop (what voltage comes out of the cable compared to what goes in) is affected by Voltage, current drawn and cable copper cross sectional area (size)

The 'normal acceptable volt drop is a maximum of 4% and nearer 2% is the target.

 

Taking 12m (one way) at 12 volts.

You will be using around 7.5 amps, lets call it 10 amps just incase you plug another phone onto charge somewhere in the circuit.

 

The wiring already existing is quite likely to be 1.5mm2 or at best 2.5mm2 so what would be the volt drop on these :

 

1.5mm2 will give 3.04 volt drop (25.4%)

2.5mm2 will give 1.80 volt drop (15.2%)

 

You need to go to 10mm2 cable which will give you a 0.44 volt drop (3.64%) just below the maximum 4%

 

Hope this helps.

 

70 AMP 10mm2 84/0.4 Stranded Thin Wall Single Core Copper Cable Wire 12V 24V | eBay

 

£1.95 per metre.

 

You may find that it will not fit into your terminals so 'work will be needed' to fit it.

 

 

OK thanks Alan. I am going to sound quite dim now but going to ask anyway 🙂 At the moment, the cable carrying the current that was supplying the extension lead debacle is showing 13.4 volts on the multimeter - this is the same as is showing on the battery charger unit. Why are they the same if there is voltage drop - I know no load is being applied at the moment but the voltage is there to be used ?

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On 21/01/2022 at 11:12, ditchcrawler said:

He also had a valve an his water tank vent and a hose adaptor on his filler so at the moorings he could pressurise the system and not need a pump.

 

 

I also knew a guy who did that. He lived aboard but knew nothing about boats and didn't realise that a mains supply would sink his boat in the event of a plumbing leak while nobody was onboard. His girlfriend was even worse. One day she knocked on a handyman neighbour's boat saying she could smell gas on her boat. The neighbour went to investigate and recoiled in horror when he saw several candles alight in the saloon! She'd lit scented candles to mask the smell of the gas! 🤣 Funny if it wasn't so potentially serious. Some people just shouldn't be on boats.

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