12v wiring question

aquaholic

aquaholic

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I want to install a freshwater pressure pump and a cigarette lighter socket and would like to know what voltage/amp cable should be used for these items.
Your would be appreciated.
 
Neil,
To give an accurate figure you need to tell us the maximum amps that each draws and the distance that they are from the supply. The higher the amps the thicker the cable, ditto for distance from the supply.
 
The current rating of the cables will depend on the rating of the pump motor and on the load you want to draw from the socket and on the length of the cable runs.

The pump should be marked otherwise consult the makers literature or website.

This site may help

Make sure you use a significantly higher rating for the wiring than you would for the same current in mains wiring as at 12 volts any small voltage drop becomes important.

Fuse the circuits as near to the source as possible to take account of the pump current rating (or better use an mcb) Similarly fuse (or fit mcb) to the socket circuit to take account of the current you want to draw from it.

I dont recommend the majority of those sockets for more than small loads although I undersatnd that Ford Dealers can supply a good one that's an accessory for commercial vehicles (Transits etc)
 
[ QUOTE ]
This site may help

[/ QUOTE ] Having now looked at it I think the calculator on that site is rubbish
 
I reckon that you are best off using the heaviest wire that will fit into connectors lugs etc. The minimum size of wire can be calculated but heavier means longer life in the corrosion atmosphere of a boat. This will probably be described as 15 amp cable. Get tinned wire if you can.
good luck olewill
 
[ QUOTE ]
Download my spreadsheet

[/ QUOTE ] Love to but I dont have Excel on this computer and I dont think it would work with the spreadsheet in MS Works.

When I get the new one on line I'll try it
 
I hope you have more luck with your cigar lighter sockets than I did when I rewired the boat. All marine quality, and would not make good contact with charger for mobile telephone, and indeed for small portable telly. Sockets in the cockpit got red hot when electric inflator used for rubber dinghy.
Replaced two sockets in the end with gold plated banana sockets from Maplin, which takes banana plugs, spade connectors and even bare wire in an emergency, all of which consistently work and dont get hot when 12 amps put though with dinghy inflator. So not only the wires need a rating... so do the sockets!
 
I agree. It's a bizarre twist of fate that the cigarette lighter has become a de-facto standard power socket. It is hard to imagine a less suitable device. It is useful to have 1 or 2 onboard, but I suggest you do anything you can tp avoid using them for any 'real' systems.
 
Thanks for all your help, the cigarette sockets I have managed to obtain are similiar to those used in ford transits as power points as opposed for just lighting your cigs.
 
Agree completely re the cigarette lighters, another auto device that has somehow found it's way onto boats. A bit like 12V electrical systems.

I made a voltage drop calculator that may help. It will either recommend a wire size (in metric and imperial) or tell you the voltage drop you will get with a selected wire type, along with the current rating in accordance to ISO 10133. Make sure you select the correct temperature rating for the isolation, as this effects the rated load quite a lot.

VoltDropCalc
 
[ QUOTE ]
I want to install a freshwater pressure pump and a cigarette lighter socket and would like to know what voltage/amp cable should be used for these items.
Your would be appreciated.

[/ QUOTE ]

One of the best cables you can use - and it doesn't need calculating etc ...... is trailer Heavy Duty cable. The stuff that caravan shops and Trailer acc's shops sell for wiring up all those items to tow bar sockets etc.
You have multiple cores and all stranded. It's designed to take punishment and also high ampage ...

For leading 12v through a boat it's very good ... with those multi-cores you have very little voltage drop as you utilise a different core for each application ... noting which is which for later fault finding.

As to Ciggy sockets / plugs ... 5 -8A is about max on most ... the cheaper ones can easily melt at that or more. I had one that was fitted by prev. owner - he used it for the Coolbox ... (7A steady ...) So I believed him and used it ... It melted later same day ... Replaced with a HD Maplins one ... and now no problem.
 
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