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Discussion Starter #1
Hi all,

I am about to install a DC DC Ctek 250se in my 2.5L Petrol 2000 Caravelle (AVT). Iv spent a bit of time running through all the wiring (Ex fire service) and Iv worked out what's what I believe. Plenty of relays leading to nothing...

My question is, is there any downfall to using larger diameter wire to link the starter battery and the ctek that what is needed according to the chart in the handbook?

I have heavy gauge battery wire (10mm dia) running from the engine bay to where the ctek wll be, I also have a narrower gauge (4mm dia) taking the same path which is what the old split charge relay system used. But as both wires are there, is bigger better?

Cheers!
 

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Bigger, the better, as long as you can fit the crimps/terminals to them.
Stated wire sizes are "minimum" that should be used....anything bigger just makes routing more difficult, BUT, voltage drops less.
Win, win if you already have the cables.
 

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Laurence.
Don't forget that the diameter of the cable is not the current carrying capacity. That is determined by the cross sectional area of the conductor.
Roger
 

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The WHOLE thing about "12 volt electrics", is the "Rated Current Capacity" is actually meaningless....it's just a safety guidance. (The numbers actually are calculated from the heating effect of the resistance...over the length of the cable....you also see different ratings as to how the cables are run...in conduit/sleeving, the numer is reduced!)
The VW T4 lighting loom is "rated" safely....and we all know how poorly that works!

Use 2.5mm CSA on 230 volts mains for 13 amps, and it may drop 2-3 volts over it's length...NO PROBLEM.
Use the same on a 12 volts system....and that voltage drop is VERY SIGNIFICANT!

When I wired a 12 metre narrow boat up....2.5 was used to feed "lights"...maybe taking 2 amps total.
The fridge was "rated" at 4.5 amps...but start-up current was over 40!
This required 10mm CSA for a 3 metre run! (IF the voltage drops when the compressor starts, it takes longer for the motor to get to speed....and REALLY does burn a load of switch gear, and the motor, out.)
Same for the 3 water pumps...MUST have as near to full voltage as possible...so as little volotage drop on the cables.
3 Amp pump....fed with 6mm CSA cable for a 5 metre run.

Forget EVERYTHING about current ratings, look at the resistance/metre....and use ohms law to calculate the voltage drop. (V = I x R)
 

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Discussion Starter #6
Thanks @Or_GazM - good advice as always. I'll use the bigger cable, given they are both installed already. I was worried about the irony of an ex fire service van setting blaze through melted wires 😅. On a very different topic, have you touched any house wiring in Norway? I changed a light switch here in Sweden and the wire colour coding made me laugh. Black being positive 😵. I used a tester for obvious reason...
 

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Have I done any wiring?.....LOL
I've rewired about 70% of the house we have (built 1940s).
Black/white, then some blue/red, or blue/brown, or...etc.
Also strange, it's 3 phase....but NOT the normal system.
Everything is connected between 2 phases to get 230 volts.
NO neutral, and the only "earth" is a copper rod in the ground outside.
The wiring method means that BOTH wires to any connection, sit at around 115 volts from earth!
Luckily I'm pretty immune to shocks, so I just use a finger to check that either or both are "live".
It's wired so that basement is between phase 1 and 2, 1st floor between 2 and 3, 2nd floor between 3 and 1......
Because there is no neutral, it's a balancing act to TRY to get the same load on each phase.

Fun thing is, possibly due to my high body resistance, those "magical" earth leakage trips never trip for me :whistle:
Current between 115 and "earth" via my body must be less than 30mA.
 

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OH....and most of the cables (both old and new....as I use the same spec cable) are actually covered in "rubber" for the 2 main wires, then a copper "earth" runs between them....
BIGGEST shock (pardon the pun) is that the whole lot is then sleeved in an aluminium sheaving, before a plastic outer!!!
Bend the cable too tight, the ally then pierces the inner insulation.....

NOTHING happens....maybe 'cos we don't have a neutral or earth comtact...
BUT...when the wife washes the wooden floor, and water gets into the wiring...makes her jump when sparks fly!!!
LOLOLOL

In UK, ALL wires for contacts must run 6" (15cm) above floor level, ALL wiring to light switches must run VERTICAL from above to down...also any wiring at ceiling height must also be 6" down from a ceiling.

ALL wires must run at 90 degrees....here in Norway, they just take the shortest route between A and B...in PLASTIC conduit....what happens if someone wants to hang a picture (or wall unit)?!?!!?
NO idea where wires could run, and plastic sleeving does zero for protection.
600mm spacing for wall joists, so all cables run up/down that joist.

Everyone says "UK plugs are so UGLY...big and bulbous"....but at least on a 30 amp circuit, a lamp that requires only 30 watts, will have a 1 amp fuse IN that "ugly plug".:geek:

SORRY for the "tirade", but you did ask....Laurence. :coffee:? (Or beer?)
 

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Discussion Starter #9
Ha ha ha, I can relate to it Or_GazM. The first time I wanted to put up some shelves I touched the drill bit onto the wall, safe in the knowledge - you run cabling vertically from the plug socket, light switch or so... Then it washed over I didn't know what the Swedes do... Dash off to buy a cable finder 😅.

I totally agree with you on the plugs. I find the 2 pin flimsy, and the majority of the outlet covers horrifying. Soon as the two tiny screws are off (hitting it with a vacuum cleaner could do it) you have exposed copper. Seems mad to me...

Glad to hear I havnt had the same amount of issues as you though, well not yet anyway. Not sure Id fancy getting shocked, or mopping the floor :)

I reversed my decision and did not use the 20mm2 battery cable that was installed, it was too stiff to move about, Van is probably 3kg lighter for it. Going to use the factory wiring for the split charge relay to power the CTEK, just need to source some fuse holders that will take a 30A and a large cable diameter. Iv been struggling as everything seems designed for audio applications (AGU fuse).

Fingers crossed Ill get it finished before summer arrives er I mean is over... :)
 
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