Member Eric posted:

weaco fridges run on 24 or 12 volts , my ac aplication is 24 V, this is why I asked if there is a difrence in fuses , are 12 and 24 V fuses the same ?Venus Bay

Member Eric posted:

Thanks eskimo , Its been working fine since i changed the fuse at 4 Pm today , Ill fill it with drinks tomorrow and see how it goes .Any idea on the fuse rating , question 2 ?Venus Bay

Member - Eskimo posted:

eric,
once had a debate about 10amp/12 versus 10amp/240 volt

The conclusion:
the fuse blows at the same current draw in both instances ( and it is'nt any different at any other voltages)

I dont know what the rating should be but your manual should tell you what the fuse protection should be. This is generally the max fuse size! but could be varied by + 5amps if absolutely neccessary

Wow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.

Member - Eskimo posted:

pick me up on the way to LD and i'll keeep your fridge going lol lolWow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.

The Publican posted:

ff90 with large compressor requires 25 amp fuse
16mm din plug is not really sufficient for ff90 fridge
if you must use a 16mm din plug and socket make sure it is hella not the cheep chinese c**P
if you keep that cigarette lighter plug you will end up with a fire
direct wire is preferable or use clipsal T plug

Member Eric posted:

I think thats a little extream isnt it ? Weaco supply something that wont work , I agree with possible bigger fuse . I will get a 12 amp tomorrow and see how it goes .

About the house grade wire , I was told that it was more efficent due to been less strands and thicker , was I misinformed ?

cheers
Venus Bay

The Publican posted:

mate if Waeco had a choice they would supply a fridge with 2 bear wires and no c**p cigarette lighter plug as they cause so much problems
you need a fuse in DC twice the starting current
mate house wire is c**p in a car and breaks internally from vibration
house wire insulation is not suitable for a car
car wire has 90c flame retardant insulation and is harder than house wire
mate square area of wire is square area and number of strands mean nearly stuff all
technically more strands are better as the outside of the wire is where the power is conducted and more strands gives larger surface area which is better.
mate the guy who told you to use house wire in a car is a dummy
for your fridge you need 6mm2 twin sheathed auto wire with a 25 amp blade fuse

Member - Eskimo posted:

I think what The Publican is trying to say is:
House wiring does not have enough strands and as such is prone to break at terminals/connection points in plugs etc. This can happen due to vibration but the incidence can get worse when subjected to man handling....

Cable size is important...Wow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.

Rosco - Bris. posted:

Just had a flash back to senior physics.

V=iR hence with 240 V cable and 30 A capacity ...
240=30*R
R=240/30
=8 Ohms (I think)

12 V cable and 30 A capacity ...
12=30*R
R=12/30
=0.4 Ohms (I think)

So would I be correct in saying you require much bigger cable in 12 V to safely carry 30 A current i.e. much less resistance.

I know there is a difference between AC and DC but the principle is more or less the same.

I may well stand corrected though .... and most probably will be.

.... ;-DFidei defensor

Rosco

Member Eric posted:

I think I need to explain myself a little better lol . The cable from battery to rear of car is , 400 amp battery cable , the house grade wire , is less than a meter long just to make the gigi lighter connection . Does this help ?Venus Bay

Rosco - Bris. posted:

Cobber I reckon the same still applies. House cable has much higher resistance (20 times if my above sums are correct). Even with a short length the fridge requires whatever watts to run, so with much higher resistance many more amps will be drawn to achieve the result, hence blown fuse.

(i think)

Fidei defensor

Rosco

Member - Captain (WA) posted:

There is no difference in the electrical resistance of AC or DC wire, its all down to the size of the wire (ie. 6.0mm2 cross sectional area) not the number of strands or size of individual strands. Copper wire has a resistance of 0.0000017241 ohm-cm (volume resistance at 20C)

Copper wire resistance is a function of cross-sectional area and say a 1.0mm2 cross sectional area (csa) wire is availble as either 1 strand of 1.13 dia or 32 strands 0.2 dia. Both have a csa of 1.0mm2 and both have a resistance of 0.019 ohms per metre and both are rated at 10 amps (for 12v dc).

AC wire is generally rated differently to automotive DC wire as AC wire has significantly longer cable runs compared to automotive DC wire. Remember, resistance is a function of distance and an automotive wire is rarely longer than 6 metres, unlike the 100's of metres in AC wire. AC wire also has twin insulation, unlike automotive DC wire which has single insulation. But a good automotive electrician will always put the dc wire in convoluted tubing to help protect it.

The 32 strand wire in the above example will be far more flexible than a single strand wire, but there is no electrical difference. Thicker individual strands generally suffer stress fatigue (vibration) and can lead to breaking. But a well supported thick strand wire will not simply break.

Also, crimping is favoured compared to soldering as a soldered joint is more prone to stress fatigue. However, the cheap crimping tools seen in discount stores give a poor crimp connection and you would often be better off soldering the connection. The proper crimping tool leaves an imprint of the connector size in the plastic cover, one easy way to tell if the proper crimping tool has been used.

In a nutshell, if wire of sufficient diameter has been used there is no pratical difference between AC or DC wire for 12V automotive use, apart from the ease of use of multi strand wire.

Cheers

Mark

(NOTE- do not apply this "general" advise to high voltage AC applications, insulator resistance becomes significant, amongst other factors).Nissan 2003 GU 3.0TD
Windsor Rapid Offroad

Nudenut posted:

at last some one who knows what he is talking about has finally taken the time to spell it out correctly.

Tinned copper wire is better than plain copper though. It doesnt corrode ie doesnt get a tarnish which can increase resistance through a terminal which can increase voltage dropI am human ...I think?
Must be....make too many mistakes!

Member Eric posted:

thanks captain , I think your on the moneyVenus Bay